Technical aspects 275
General EUS examination technique 281
EUS-guided FNA 282
How to examine tumors of the esophagus and mediastinum 286
How to examine the stomach 289
How to examine the pancreaticobiliary region 291
How to examine the anorectal region 308
Ultrasound terminology 310
Endosonography in gastrointestinal oncology 314
Pancreatic disease 326
Biliary EUS 350
Assessment of submucosal tumors of the digestive tract 353
Assessment of other GI disorders 362
Celiac plexus neurolysis (EUS-CPN) 363
Drainage of pancreatic fluid collections (PFC) 365
EUS fine-needle injection and fiducial placement 369
Endoscopic ultrasound (EUS) is firmly established in the locoregional staging of cancers of the esophagus, stomach, pancreas, extrahepatic bile duct, anal canal, and rectum.
EUS is complementary to cross-sectional imaging, e.g. CT, MRI, PET in the evaluation of GI cancers and benign pancreaticobiliary disease.
It also has a major role in the diagnosis and management of submucosal lesions of the GI tract, choledocholithiasis, chronic pancreatitis, and cystic pancreatic lesions.
A thorough understanding of anatomy and experience are key to accurate EUS performance.
Radial and linear EUS are complementary: for many indications, radial examination is easier to learn and quicker to perform; linear EUS is necessary for performing FNA biopsy.
Interventional EUS is a key component of modern EUS.
EUS-FNA is safe with a major complication rate of <1%.
EUS-FNA will yield a diagnosis in >80% of solid masses.
Optimum handling and preparation of cytology samples is critical for diagnosis.
EUS is the preferred method for performing celiac plexus neurolysis.
EUS-guided drainage of pancreatic pseudocysts offers many potential advantages over other methods.
Therapeutic EUS relies on a combination of EUS imaging and other endoscopic procedures, e.g. guidewire exchanges and stent insertion.
Further new roles for therapeutic EUS are likely to be developed soon, but will require new accessories and devices and possibly modified echoendoscopes.
By introducing a miniature ultrasound probe into the gastrointestinal tract, bringing the structure to be examined close to the transducer, high frequencies can be used, achieving a satisfactory compromise between excellent image resolution and the resulting poor depth of field that can be assessed. Endoscopic ultrasound (EUS) is a particular aspect of gastrointestinal ultrasonography, since the miniature transducer is placed at the tip of an endoscope equipped with video optics. Gastrointestinal endosonography began in the mid-1970s, was developed in the mid-1980s, and is now used in current practice in gastrointestinal oncology, but also in the diagnosis of biliary obstruction and in assessing neoplastic and inflammatory disorders of the pancreas. Several other less common indications have been developed, for example submucosal tumors of the gut wall, portal hypertension, esophageal motor disorders and assessment of various anorectal and gynecological disorders, in particular deep subperitoneal endometriosis.
This imaging technique, which has the highest resolving power currently available for evaluating the digestive tract wall and the organs in contact with it, has undergone a rapid evolution in the last decade with the development of EUS-guided histology, the development of EUS-guided therapeutic techniques and the advent of technological refinements such as elastography and contrast-enhanced EUS.
It is important to bear in mind that this imaging technique, in which the quality of the results depends directly on operator experience, requires considerable investment in terms of diverse, expensive equipment, long specific training (except for therapeutic endoscopic ultrasound which is easy for an interventional endoscopist to learn) and finally the recruitment of many types of personnel. Its use is therefore justified only at referral centers where all these conditions are met.
Although therapeutic endoscopic ultrasound is the most exciting part of the technique, it is not currently in widespread use because of the limited indications and small number of patients who may benefit from it.
Diagnostic EUS and EUS-guided FNA thus remain more than ever the main applications of the technique and are its future in the short and medium term.
The resolving power of an ultrasound probe is directly proportional to the frequency emitted: with a frequency of 7.5 MHz, widely used in EUS, the spatial resolution is in the order of 1 mm. On the other hand, the depth of field that can be analyzed is inversely proportional to the frequency used ( Table 1 ).
|Frequency (MHz)||Depth of field (cm)|
In recent years, equipment manufacturers have increased the range of frequencies that can be used on the same endoscope by adding relatively low frequencies (5 and 6 MHz), which allow accurate analysis to a depth of 6–8 cm, thus achieving better management of some pancreatic disorders.
Two types of ultrasound technique are used in endoscopic ultrasound.
Radial imaging provides 360° ultrasound images perpendicular to the axis of the endoscope.
This technique has many advantages, namely:
Excellent image quality, allowing real-time study of the circumference of the digestive tract through 360° ( Fig. 1 ), making the examination easier overall for all types of gut pathology, particularly for assessing locoregional involvement of cancers and their surveillance or other indications related to diseases of the gastrointestinal wall
The ability to visualize constantly the major vascular landmarks, facilitating localization of pathology regardless of the oblique optics of the ultrasound image obtained, thus allowing precise evaluation of the structures and organs around the intestinal lumen, particularly the pancreaticobiliary region.
Its main drawback is that it is impossible to carry out EUS-FNA as the path of the needle passes through the plane of the ultrasound image and cannot therefore be monitored in real-time.
Because radial imaging is long-established and relatively easy to perform, it currently remains the most widely used EUS technique. Three types of apparatus have been developed as a result:
Video-EUS ( Fig. 2 ) for the study of the esophagus, stomach, duodenum, pancreaticobiliary region, anal canal, rectum and colon, with the option of simultaneously visualizing the ultrasound image and the endoscopic image. There are two types of radial video-EUS:
Rotating mechanical: this is the oldest type (developed in the early 1980s). It is used increasingly rarely and Doppler studies are not possible.
Electronic in B-mode. The three companies that manufacture echoendoscopes supply this type of apparatus. The endoscopic view is either end-viewing (Pentax, Fig. 2A , or Fujinon, Fig. 2B ), or oblique-forward (Olympus, Fig. 2C ). The instruments produce several frequencies (5–12 MHz) and thus allow Doppler studies and power Doppler sonography. The latest instruments, which are connected to very sophisticated ultrasound consoles, allow contrast harmonic ultrasound after intravenous injection of ultrasound contrast agents.
Rigid probes are designed for examination of the anal canal and its sphincters and the lower and mid-rectum. Both rotating mechanical or electronic transducers are available.
Miniprobes ( Fig. 3 ) can be introduced into the operating channel of conventional endoscopes, and are particularly suited to the use of very high frequencies (20 and 30 MHz). They were developed in the mid-1990s, and are used before curative endoscopic treatment of superficial flat cancers of the digestive tract (0–IIa, b, c) and high-grade dysplasia; these very high frequency miniprobes allow accurate patient selection for curative endoscopic treatment of superficial cancers whether for endoscopic mucosectomy, submucosal dissection, photodynamic therapy or radiofrequency ablation.
Mid-way between the miniprobe and the echoendoscope, is the ‘blind’ probe ( Fig. 4 ; Box 1 ), a flexible instrument with a small diameter (7.8 mm) and lacking endoscopic optics, with a miniature transducer at its end; it uses the rotating mechanical radial technique, emitting at 7.5 MHz, and is tapered at its end (3 mm). The blind probe can be passed over a guidewire previously positioned under endoscopic control. It is intended for the examination of stenotic esophageal or rectal lesions.
For the esophagus, use a transnasal or pediatric gastroscope, which can pass through the stenosis without previous dilation. Aspirate the air present in the gastric lumen, position a 0.035 inch guidewire in the stomach, withdraw the endoscope, slide the blind probe onto the guidewire and insert, under ultrasound control, into the stenosis, moderately inflating the balloon to facilitate its passage. Then advance the probe into the stomach (celiac region). The examination is performed by withdrawing the probe under ultrasound control as far as the cervical esophagus.
Curved linear array ( Fig. 2 )
The ultrasound image obtained in electronic B mode is a sagittal image ( Figs 5, 6 ) provided by an electronic transducer. The plane of the image is parallel to the axis of the endoscope.
The main advantage of this technique is the ability to carry out intra- or transmural EUS-guided FNA ( Fig. 7 ) as the path of the needle to the target can be followed in real time on the ultrasound image.
As a result of this option, therapeutic EUS uses echoendoscopes with a large operating channel.
The drawback of this type of equipment is the nature of the sagittal images as these are inappropriate for studying the circumference of the GI tract and thus assessing locoregional involvement prior to treatment or surveying cancers of the GI tract.
Two types of instrument use this technique: video-echoendoscopes and rigid probes.
Video-echoendoscopes can be used to study the esophagus, stomach, duodenum, pancreaticobiliary region, anal canal, rectum, and colon. They are less suited to examining the esophagus, common bile duct, anal canal and rectum than instruments using the radial technique, because of the nature of the images obtained. They are also more difficult to use for the stomach and duodenum. On the other hand, they allow very satisfactory examination of the pancreas and the peripancreatic region, particularly its vascular aspect, and the posterior mediastinum.
Rigid probes are designed for examination of the anal canal and rectum. Although the image obtained is not very practical for studying the anal sphincters and the pre-treatment assessment of rectal and anal cancers, it nevertheless allows an accurate measurement of the distance between the lower margin of a rectal cancer, the pelvic floor and the internal anal sphincter, thus providing valuable information on whether intersphincteric resection is indicated for low rectal cancers. Rigid probes are also very well suited to dynamic studies in patients with pelvic floor disorders since they allow the simultaneous examination of the lower part of the anterior rectal wall, the anal sphincters, the urethra and bladder, and the rectovaginal septum. Hitachi consoles can provide a useful three-dimensional evaluation of the mesorectal region.
Sedation analgesia and general anesthesia
EUS, even if performed without FNA sampling, usually requires intravenous sedation or light general anesthesia because the procedures can be prolonged and require the patient to remain completely still. The use of a benzodiazepine (Midazolam) may be sufficient for examination of the esophagus, stomach and mediastinum. Combining this with an opiate or Propofol, to produce short-term general anesthesia may be necessary for pancreaticobiliary examination or for any EUS-FNA, depending on local custom. This means that EUS needs to be performed at centers with appropriate outpatient facilities.
In contrast, endorectal or endoanal ultrasound without FNA may be performed without sedation (except for painful cancer of the anal canal, or perianal abscess or fistula).
How to position the patient, doctor, and console
For gastroesophageal or duodenal examination, the left lateral decubitus position is usual. The patient’s head and chest may be raised if water is instilled into the stomach or duodenum.
For pancreaticobiliary examination, left lateral decubitus, tilted forwards by 30°–45°, is the best position ( Fig. 8A ). The left shoulder should therefore be moved back and the right leg brought to the front. If the patient is very thin, it is often useful to have him/her lie almost prone, to examine the common bile duct and pancreatic head.
For anorectal examination, supine is the simplest position. Instilled water pools at the most dependent point and therefore indicates the posterior wall of the lower and mid-rectum at the bottom of the screen, and the anterior wall at the top of the screen, the right wall to the right of the screen and the left wall to the left of the screen.
If there is a second monitor in addition to the console screen and this is positioned behind the patient’s back, the examiner is usually facing the patient, at an angle of 45° facing the patient’s feet when he has to use an open handle position, or at an angle of 45° facing the patient’s head when he has to use a closed handle position. This is the most ergonomic position for the examiner, regardless of the position of the console which can be positioned either close to the patient’s head or by the patient’s legs.
If there is no second TV monitor, the examiner’s position will depend on the position of the console (see below).
Position of the echoendoscope handle
Definitions concerning the position of the echoendoscope handle:
The neutral position ( Figs 8B, 9 ) is where the front of the handle is facing the patient.
The open position ( Figs 8C, 9 ) is where the front of the handle is facing the patient’s feet. It is reached by turning anti-clockwise through 90° from the neutral position.
The closed position ( Figs 8D, 9 ) is the opposite of the open position. It is reached by turning clockwise through 90° from the neutral position.
The extreme closed position ( Figs 8E, 9 ) is reached by continuing to turn the handle clockwise through a further 90° by shoulder rotation, bringing the handle opposite the neutral position.
The neutral and open positions account for at least 75% of the positions used for pancreaticobiliary and rectal examination.
The closed position is used to examine the pancreatic tail and is one of the three positions used to examine the uncinate process of the pancreas.
The extreme closed position is used for pancreatic tail biopsy and is one of the three positions used to biopsy the uncinate process of the pancreas.
When the ultrasound console is at the patient’s head ( Fig. 10 ), the closed position of the handle (facing the console) is used for examination of the posterior mediastinum: the spine and the aorta (posterior) being at the bottom of the screen and the left atrium (anterior) at the top of the screen; the right side of the screen then corresponds to the left of the posterior mediastinum and the left side of the screen to the right of the posterior mediastinum.
When the console is at the patient’s feet, the open position ( Fig. 11 ) of the handle (which is facing the console) is used ( Fig. 8F ) for examination of the posterior mediastinum: the spine and aorta (the back) are at the top of the screen and the left atrium (the front) is at the bottom of the screen; the right side of the screen then corresponds to the right side of the posterior mediastinum and the left side of the screen to the left of the posterior mediastinum.
The console position is unimportant if there is a second monitor positioned behind the patient’s back. If not, you can choose between the top and bottom of the patient.
The majority of endosonographers place the console (and therefore the screen) at the patient’s head ( Fig. 10 ), i.e. to the right of the examiner when he/she is facing the patient. As such, the most natural position of the handle is facing the screen, which corresponds to the closed position described. For the handle to face the patient, i.e. in the neutral position, it must be turned anti-clockwise through 90° from the most natural position and this is not problematic. On the other hand, it is difficult to continue to turn the handle anti-clockwise through a further 90° to reach what is described as the open position because the screen is then 180° opposite this position.
It is because the neutral position and the open position account for three-quarters of the positions that are useful for pancreaticobiliary and rectal examination that this console position has not been considered.
It is advisable to place the console alongside the patient’s legs ( Fig. 11 ). The open position of the handle ( Fig. 8C,F ) is therefore the natural position, because the examiner is then positioned at an angle of 45° in relation to the screen. The neutral position ( Fig. 8B ) is easy because the examiner is then facing the patient. The closed position ( Fig. 8D ) is easy because the left hand, which is holding the endoscope handle, is up against the examiner’s right clavicle and you are facing the patient. Only one handle position is uncomfortable for the examiner when the console is placed at the patient’s feet: this is the extreme closed position ( Fig. 8E ), i.e. with the handle opposite the patient. It is then difficult to see the screen positioned along the patient’s legs, while maintaining this extreme closed position for any length of time. This handle position is useful only for biopsying certain tumors of the uncinate process and pancreatic tail. In these two situations, it is advisable to change the position of the console and place it at the patient’s head.
It is best to have a second monitor positioned behind the patient’s back
Otherwise, it is best to position the console beside the patient’s legs, since this facilitates pancreaticobiliary and rectal examination ( Fig. 12 ) in which the extreme closed position is rarely used and since this does not complicate esophageal or mediastinal examination; on the contrary, the right side of the screen corresponds well to the right part of the patient’s mediastinum and the left side of the screen to the left part of the patient’s mediastinum.
General EUS examination technique
EUS examination uses two different methods that are sometimes combined to obtain a satisfactory acoustic window between the transducer and the gut wall, as well as the surrounding region. The first is the balloon method, and the second is the instillation of water through the operating channel of the echoendoscope.
The balloon technique is often essential for the examination of the esophagus, the adjacent mediastinum, the duodenum and the adjacent pancreaticobiliary region, but also for the anal canal, rectum and sigmoid colon as well as of the surrounding pelvic area. The balloon method is also used alone for the stomach after aspiration of the air present, for examination of the antrum, where this technique is sufficient, but also for examination of the pancreatic neck, body and tail, the left liver lobe or the spleen.
The instillation of water into the gut lumen is a technique used mainly in the stomach for the examination of the gastric wall, body and fundus, and for the characterization of wall lesions (thickened gastric folds, cancer, lymphoma or submucosal tumor). It is also useful for the examination of minor lesions of the duodenum or the ampulla of Vater region.
Because of the risk of pulmonary aspiration, the volume of sterile water instilled into the upper GI tract at EUS must never exceed 100–150 mL.
The use of deaerated water (i.e. boiled and cooled beforehand) is preferred for the examination of small superficial lesions in the stomach, because the acoustic window is far better. Water instillation is required for examination of rectal lesions, since this allows the endoscope to reach and pass the rectosigmoid junction (where the examination should begin) without the need for air instillation, i.e. without the need to view the wall endoscopically during progression, being guided simply by the stream of water instilled into the rectum, so as not to impair the ultrasound examination. The use of deaerated water is particularly useful for villous tumors or superficial cancers.
Examination technique using miniprobes
The miniprobes are introduced into the endoscope operating channel and slid in endoscopic view over the lesion to be studied:
For the stomach, 100–150 cc of deaerated water should be instilled. Examination is easy, the images are very clear and interpretation is usually easy, except for the angularis incisura which should be examined after positioning the patient prone.
For the esophagus, an ultrasound interface needs to be created between the miniprobe and the esophageal wall. This can be done with either a purpose-designed disposable balloon (Olympus) which requires the use of an endoscope with a large operating channel, or a condom fixed to the end of the endoscope; the condom can then be filled with water using a catheter previously attached along the endoscope. The best technique is to flood the esophagus with deaerated water, which requires tracheal intubation of the patient beforehand. Paralysis of esophageal peristalsis is often necessary, using intravenous atropine or glucagon.
Examination of the bile and pancreatic ducts has also benefited from the introduction of miniprobes. Miniprobes are available mounted on a guidewire, and these can be introduced into the desired duct without previous sphincterotomy. This type of technique can be used only in an interventional endoscopy room equipped with fluoroscopy and with the ability to produce X-ray images.
The blind probe used in cases of stenotic esophageal or rectosigmoid cancers requires prior introduction of a guidewire through the stenosis, under endoscopic control. The air introduced during endoscopy must be carefully aspirated, because the blind probe has no suction channel. The probe is then advanced over the guidewire into the stenosis and positioned beyond it. Examination takes place as the probe is progressively withdrawn.
Indications and contraindications
There is a broad range of indications for EUS-FNA and these are outlined in Box 2 .
These indications will continue to evolve, especially with advances in oncology, e.g. restaging after neoadjuvant therapy or to provide tissue for molecular genetic analysis to guide treatment and/or prognosis.
N1 or M1 lymph nodes (LN) in patients with primary esophagogastric cancer.
Evaluation of pancreatic cystic lesions.
Mediastinal LN (N2 or N3) in patients with known or suspected lung cancer.
Mediastinal masses of unknown etiology.
Retroperitoneal LN or masses.
Perirectal LN or masses.
Lesions in the left lobe of liver.
Left adrenal masses.
Thickened gastric or intestinal wall with negative mucosal biopsies.
These are few and are listed in Box 3 .
Severe coagulopathy or thrombocytopenia.
Inability to visualize lesion clearly.
Large interposed vessels.
Risk of tumor seeding, e.g. resectable pancreatic body or tail lesion.
The needles are disposable and designed for single use.
22 G Needle. A 22-gauge needle is used for pancreatic and lymph node fine-needle biopsy (if the lymph nodes are small) and for pancreatic cystic tumors.
19 G Needle. A 19-gauge needle is recommended when biopsying a submucosal tumor of the digestive tract, or a large mediastinal lymph node. A 19-gauge needle can be used to obtain a true core biopsy, which is useful if a stromal tumor or lymphoma is suspected since this helps histological interpretation. The 19-gauge needle is difficult to use because it is fairly stiff and usually cannot be used for transduodenal biopsy. The stylet must be routinely withdrawn by 5 mm to pass through the wall.
25 G Needle. 25-gauge needles have recently become available, and are mainly indicated for sampling tumors of the uncinate process of the pancreas which are sometimes difficult to reach in the short position and require a long position with extreme angulation in the second part of the duodenum. They can also be used for hypervascular tumors and particularly for biopsying renal cancer metastases or endocrine tumors. These needles provide better, less hemorrhagic cytological smears and they are therefore preferred when working without a specialist cytopathologist. On the other hand, the sample obtained for a cell block preparation is poor. The 25 G needle is not widely used in Europe, where it is unusual to have a cytologist present in the examination room and where cytologists are usually cytopathologists who prefer to work on high-quality cell blocks.
Tru-Cut 19 G Needle. A 19-gauge Tru-Cut needle is available (Cook Medical), which provides a true core biopsy. It is indicated for submucosal tumors, lymph nodes when lymphoma is suspected, and in the pancreas when autoimmune pancreatitis is suspected. It cannot normally be used in the duodenum owing to its rigidity. The path of the lesion to be biopsied must be at least 20 mm long for it to be biopsied safely. Unfortunately, this device has not been as effective as it could be, it is costly and for this reason it has not replaced the 19 G needle in many centers.
22 G – the most widely used needle: mediastinum, celiac region, pancreaticobiliary region including the uncinate process of the pancreas, submucosal tumor and rectum. Allows cytology and histology (cell block preparation).
19 G: cannot be used in the second part of the duodenum, allows cytological study, histological study by cell block preparation and often a core biopsy. It is particularly useful for submucosal tumors, large lymph nodes (suspected lymphoma or sarcoidosis) and autoimmune pancreatitis. It is essential for therapeutic EUS since it allows the insertion of a 0.035 inch guidewire before interventional procedures.
25 G: can be used for all EUS-FNA indications. It is particularly useful for hypervascular tumors and tumors of the uncinate process of the pancreas. It provides better cytology (less bloody) but poorer histology (poorer quality cell block) for solid pancreatic lesions.
Tru-Cut 19 G: It is particularly useful for submucosal tumors, large lymph nodes and autoimmune pancreatitis because it can theoretically provide a core biopsy. It is not always effective and design improvements are required.
EUS-FNA requires adequate sedation or general anesthesia and patient monitoring for at least 4–6 h afterwards. Many factors influence the success of EUS-FNA ( Box 5 ).
Nature of lesion – metastatic LN → solid pancreatic masses.
Operator experience: success increases after at least 50–100 cases.
Needle size: 25 G needle may have higher yield for solid pancreatic masses.
Sample preparation technique.
Presence of rapid on site evaluation: maximize yield of adequate specimens.
Before undertaking EUS-FNA, check by power Doppler imaging that there is no vessel in the intended path of the needle. Before removing the needle from the sheath, check endoscopically that the sheath around the needle is visible, but only barely visible.
Upwards deflection of the scope tip keeps the transducer tip pressed against the wall and creates a shallow exit angle for the needle. The needle is advanced from its sheath and applied against the gut wall at an exit angle pre-determined by the endoscope being used. The path of the needle towards the target must take account of this predetermined angle making pre-positioning of the echoendoscope in relation to the target essential. Once pre-positioned against the wall, it may be necessary (depending on the needle type) to retract the small central stylet by 5 mm (if there is a blunt end) in order to be able to pass through the wall, especially with 19-gauge needles.
The latest generation Olympus and Pentax echoendoscopes have an elevator and are therefore easier to handle than older echoendoscopes, because the angle of passage through the digestive wall to the target can be adjusted. This is particularly useful for lesions that are difficult to access, notably those of the uncinate process, for lesions remote from the digestive wall (more than 15 mm away), or for very small lesions (≤1 cm in diameter). The Fujinon echoendoscope has a virtual target line ( Fig. 7C ) that shows the operator the path the needle will take. The exit angle of the needle is very shallow and is comparable, without an elevator, to that provided by Olympus and Pentax instruments when used with their elevators.
The value of intravenous antibiotic prophylaxis is debatable for solid lesions unless indicated for prevention of infective endocarditis. Antibiotic prophylaxis is essential for biopsy of a cystic lesion, whether of the pancreas or digestive wall. It is also required if the patient is using gastric antisecretory drugs (PPI) since this type of product encourages gastroduodenal microbial overgrowth. Antibiotic prophylaxis is also required for transrectal FNA. The antibiotic therapy must be continued orally for 3 to 5 days.
Should be given by the intravenous route.
Before biopsy of cystic lesion including cystic pancreatic lesion.
If the patient is taking gastric antisecretory medication.
Before transrectal biopsy.
Must be continued orally for 3–5 days.
Use amoxicillin-clavulanic acid or a second- or third-generation cephalosporin, or a latest-generation quinolone.
Pancreatic cancer biopsy
A 22 G needle is advanced under ultrasound control into the tumor. Once in position, the stylet, if it has been partially retracted, is pushed back into the needle so that any fragment of the digestive wall present at the tip of the needle will not obstruct it; the stylet is then removed completely and a 10–20 cc syringe, preferably with a continuous negative pressure instrument, is fitted to the needle. Once continuous negative pressure has been obtained, the needle should be moved slowly to and fro several (about 20) times in the lesion without hurrying, without removing the needle from the lesion, and trying, if possible, to change the angle of penetration of the lesion; this is helped by having an elevator, if the target is small and close to the lesion or if the lesion is soft, which is rare in cancer of the pancreas; if, as is more common in pancreatic cancer, the lesion is large, far from the probe or hard, angulation of the endoscope should be adjusted (from up to down angulation) to change the path of the needle in the lesion.
The needle must always be monitored in real time on the screen, during these movements, to avoid vascular or organ injury. To be sure that the needle is correctly centered in the lesion during aspiration, make small clockwise and anti-clockwise movements of the handle. Avoid penetrating any vascular and particularly arterial structures which may be present between the digestive wall and the target. Power Doppler imaging should be used for this purpose. On the other hand, unexpected passage through intramural or adjacent collateral venous circulation does not usually cause any significant complications if the vein is <3 mm in diameter. As little healthy pancreatic tissue should be traversed as possible, in order to limit the risk of acute pancreatitis. It is also advisable to avoid penetrating the common bile duct and main pancreatic duct, particularly if the latter is dilated upstream of a tumor, since the risk of acute pancreatitis is then increased. Do not puncture the gallbladder or the common bile duct above the pancreas owing to the risk of biliary leakage. Once the biopsy has been completed, release the negative pressure otherwise tumor cells may be deposited in the needle tract as it is withdrawn. Once negative pressure has been released, the needle is withdrawn into its protective sheath and the EUS-FNA needle is removed from the operating channel of the echoendoscope, which is left in position over the lesion. The biopsy sample is then checked. It is ideal to have a cytologist present in the biopsy room since he/she can immediately assess the quality of the sample. If there is no cytologist available, several biopsy passes (two to three on average) should be made in the tumor. The sample should preferably be placed in a tube containing formaldehyde or formalin so that histology can be performed on a cell block preparation. For this purpose, the stylet is advanced through the needle, gradually expelling the sample. Once a sufficient sample has been obtained for histological study, the remainder is divided, giving preference to smears (two to three slides should be prepared), and the rest is placed in CytoLyt medium for liquid-based cytology. This is particularly useful if the sample is poor or liquid, as in cystic tumors of the pancreas. Liquid-based cytology involves the automated concentration of the cells and produces a slide that is easy to process with a thin, even layer of cells. Liquid-based cytology can also be used for immunohistochemistry, unlike slide smears. Once the three types of sample have been obtained, the stylet should be withdrawn and the needle purged, using a 10 cc syringe filled with air, onto slides, yielding a further 1–3. The inside of the needle should be purged with 30 cc of physiological saline between biopsies. If the same patient with pancreatic cancer has several targets, the procedure should start with a biopsy of a hepatic metastasis, then a lymph node biopsy and finally the tumor itself. For lymph node biopsies, start with the lymph node least likely to be involved by tumor and end with the most suspicious.
The biopsy procedure must be stopped if blood is aspirated into the syringe.
If the pancreatic cancer is very hard and the sample is very poor (just some serous fluid) and there is no cytologist available in the examination room, a 50 cc or 60 cc suction syringe should be used. For cancer of the pancreatic body or tail, the needle can also be changed for a 19 G needle combined with a 50 cc or 60 cc suction syringe.
Biopsy of a cystic lesion
For a cystic lesion biopsy, puncture only once to avoid introducing infection. A cystic lesion should be punctured boldly and cleanly by quick, firm pressure so as not to tear the wall (this can happen if you push in the needle slowly while the patient’s respiratory movement causes the lesion to move). After withdrawing the stylet, attach a 10 or 20 cc suction syringe, according to the volume to be aspirated. If no fluid is visible after a few seconds, check that the needle is positioned correctly. If it is, wait because this means that the fluid is viscous (IPMN or mucinous cystadenoma).
Where possible, i.e. if the cystic lesion is not too large, it should be drained completely, in particular if it is a cystic lesion of the pancreas. Cystic lesions of the mediastinum, esophagus or rectum should not be punctured since several cases of abscess formation and in particular mediastinitis have been reported in the literature. The same applies to infected necrosis following acute pancreatitis.
Lymph node biopsy
For lymph node biopsy, adjust the needle and sampling technique according to the suspected nature of the lymph node and its size.
For a large lymph node with suspected lymphoma or sarcoidosis in the mediastinum or around the stomach, use a 19 G needle, moving it back and forth a number of times (about 20) without suction, then end with suction with a 10 cc syringe for just a few movements. Give preference to cell block preparation and place part of the sample in an appropriate fluid for the study of lymphocyte populations by flow cytometry.
For a lymph node that is a suspected metastasis from a gastrointestinal or pancreatobiliary (non-endocrine) cancer, use a 22 G needle adopting the same procedure for the first pass as described for the 19 G needle. If the sample from the first pass is poor, use a 20 cc suction syringe for the second pass and begin to aspirate after just a few back and forth movements without suction and carry out about 30 back and forth movements with suction. Preference should be given to liquid-based cytology if the sample is poor and to cell block preparation if the sample is hemorrhagic. If the sample is rich (presence of whitish material), smears and cell block preparation should be preferred.
If a lymph node metastasis from an endocrine tumor is suspected, use a 22 G or 25 G needle (depending on whether you are working with a cytopathologist or a cytologist), carry out numerous back and forth movements without suction, then aspirate with a 2 cc or 5 cc syringe during a few back and forth movements. If the sample is very hemorrhagic and a 22-gauge needle has been used, use a 25-gauge needle for the second pass with even less or no suction at all. If the sample is poor, use a 10 cc suction syringe and aspirate more vigorously (10–20 back and forth movements).
Some lesions are difficult to biopsy, for example some benign or malignant pancreatic tumors, either because they are hard (or very fibrotic) or because they are very small (usually endocrine tumors), because they are far from the gut wall, or because they are in areas where the needle has little penetration force.
Biopsy of the uncinate process of the pancreas
In this case, the endoscope is sometimes looped in the long position in the second part of the duodenum so that the biopsy path avoids the dilated common bile duct or the dilated pancreatic duct, or because it is the only way to approach the target with the echoendoscope. Looping the echoendoscope in the second part of the duodenum prevents the needle leaving its protective sheath and reduces the exit angle of the needle, so that the combination of these two factors limits penetration force into the lesion. This technical problem is best solved by using echoendoscopes with a large operating channel (therapeutic echoendoscope), using new latest-generation Teflon-coated needles with lower friction, or by using 25 G needles.
During FNA sampling of hard lesions or where the tip of the echoendoscope is acutely angulated, the needle may become bent, making it difficult to visualize during further passes. Always check the needle and reshape it so that it is straight between passes.
Biopsy of the pancreatic neck
Patients with a long stomach usually require more than 50 cm of the echoendoscope to be introduced so that it is positioned in the stomach over the lesion. The biopsy path towards the target is then at a tangent to the gut wall (distal lesser curve), which reduces penetration force and causes, when the needle is advanced, the gastric wall and the lesion to move, without the needle penetrating the lesion. The echoendoscope, which is lying along the posterior side of the lower vertical lesser curve, tends to withdraw to the greater curve as the needle attempts to puncture the wall. An elegant way of resolving this problem is to accelerate the puncture of the needle through the wall into the lesion, using a sudden, firm thrust, having previously measured the distance between the wall and the lesion, so as to limit the penetration of the needle by means of the adjustable lock on the handle. This avoids accidentally passing through the target. An alternative effective way of biopsying neck tumors is to position the echoendoscope in the duodenal bulb and hyper-inflate the balloon then withdraw the echoendoscope to 50 cm from the incisors, leaving the tip in position in the bulb. The neck and the lesion then appear under the transducer, and the needle exits immediately upstream of the pylorus into the distal antrum. Full penetration of the needle can then be obtained either by pushing the needle progressively towards the tumor or using a sudden, hard thrust.
Renal cancer metastases and endocrine tumor
The biopsy technique for a pancreatic mass suspected of being an endocrine tumor or a renal cancer metastasis must be different as regards the suction force exerted. Make several back and forth movements without suction, then lightly aspirate using a 2 cc syringe for 1–2 s. Cells from this type of cancer, which are very fragile, thus remain analyzable. This also lowers the risk of post-biopsy hematoma (see Fig. 138 ) associated with these hypervascular tumors.
Complications of EUS-FNA
EUS without FNA can be performed on patients receiving anticoagulant treatment in the therapeutic range. It does not require specific antibiotic prophylaxis. Provided the duodenal anatomy is normal and compliant, diagnostic EUS has no specific complications compared with conventional upper GI endoscopy.
The main complications of EUS-FNA are superinfections of pancreatic cystic lesions, pseudocysts and other cystic lesions (bronchogenic or foregut duplication cysts). Bleeding and, in particular, hematomas in the gut wall or in biopsied cystic lesions have also been described, but without major consequences. A few cases of pancreatitis have been described, mainly after biopsy of a benign pancreatic lesion (cystic tumor, IPMN of the uncinate process or endocrine tumor), where it was necessary to pass through healthy pancreatic tissue, whereas the risk of pancreatitis is very low in pancreatic cancer biopsy. Complications of EUS-FNA occur in 2–6% of cases. These complications are very rarely severe, for example complicated acute pancreatitis. Mortality is estimated at 0.2% and is observed almost exclusively in EUS-FNA of benign pancreatic lesions.
To summarize, EUS-FNA is an invasive technique with low morbidity but it is nevertheless associated with a small number of severe complications.
BEWARE! Do not perform FNA of mediastinal cystic lesions: abscess or mediastinitis can occur.
How to examine tumors of the esophagus and mediastinum
After upper endoscopy (EGD) to identify the location of the tumor (distance from the incisors, length, circumferential involvement, degree of stenosis and ulceration), EUS begins in the stomach, 45–50 cm from the incisors, over the posterior side of the lesser curve, at the junction between the upper and middle thirds of the lesser curve. The echoendoscope must be pressed (by up angulation) against the lesser curve, between the liver (segment II) and the junction between the pancreatic neck and body. The air present in the stomach must have been completely aspirated beforehand, especially if EGD has been carried out previously.
The celiac region and the subcardial and left gastric artery lymph node areas are examined by progressively withdrawing the echoendoscope, keeping the transducer pressed against the wall by up angulation of the scope tip.
The anterior subcardial lymph node areas between the anterior surface of the upper part of the stomach and the apex of the left lobe of the liver should also be examined. The splenic hilum should also be examined; this can be a drainage region, in the event of subcardial involvement by esophageal cancer, following the splenic artery and vein to the spleen. If a suspicious lymph node is discovered in the celiac region, the examination should be continued as far as the second part of the duodenum, to examine the retroduodenopancreatic and lumbar aortic lymph node areas and the hepatic pedicle, which may be affected.
By withdrawing the instrument into the posterior mediastinum, the esophagus and peri-esophageal region can be visualized:
Over the lower third, i.e. below the left atrium, between 40 and 35 cm from the incisors
Over the left atrium, between 35 and 30 cm from the incisors
Over the subcarinal region, the carina and the arch of the aorta, between 30 and 23 cm from the incisors
In the supra-aortic and upper thoracic region between 23 and 20 cm from the incisors
In the cervical region ( Fig. 13A,B ) between 20 and 16 cm from the incisors.
Generally speaking, the lymph node drainage areas of esophageal cancers are often ipsilateral (right or left) to the predominant spread of the cancer on one or other of the lateral walls.
Five major regions should be examined very closely for metastatic adenopathy. They are, from the top down:
The cervical region, below the thyroid lobes, in the right and left tracheo-esophageal angle
In the upper thorax, latero-esophageal region and tracheo-esophageal angle ( Fig. 13C ) between 18 and 22 cm from the incisors above the aortic arch
In the aortopulmonary window ( Fig. 13D ), below the inside edge (right) of the aortic arch between the left side of the esophagus, the anterior part of the origin of the descending aorta, the left pulmonary artery, the termination of the trachea and the origin of the left main bronchus
In the subcarinal region ( Fig. 13E ), behind the right pulmonary artery, which crosses the anterior side of the esophagus, and behind the upper part of the left atrium
Over the lower third and the junction between the middle third and the lower third of the esophagus, and the peri-esophageal region, particularly the posterior part.
Tumor stenoses are impassable in only a few cases if a gastroscope has passed through beforehand. If a stenosis is impassable, a blind probe, capable of passing through almost 95% of malignant stenoses, should preferably be used. If a blind probe is unavailable, cautious dilation can be considered. Dilation up to a diameter of 13 mm is usually sufficient to allow the latest generation echoendoscopes to pass through. This type of dilatation is usually safe. The use of a 7.5 or 12 MHz miniprobe is a less satisfactory alternative to a blind probe.
Special features of radial examination
While studying an esophageal tumor using a radial echoendoscope fitted with a balloon, the balloon should be inflated moderately so that the endoscope can be advanced and retracted without creating an oblique image. The endoscope should be kept angulated so that the transducer remains perpendicular to the lesion examined. This means making sure that the muscle layer is visible through 360° around the lesion examined. For a small lesion, the inflated balloon should be positioned between the lesion and the transducer, with the aid of sufficient angulation so that it is not pressed against the lesion.
Left lateral decubitus.
Use a moderately inflated balloon (15–20 mm in diameter).
Begin the examination in the stomach over the celiac region.
Bring the scope up to the cricoid cartilage (landmark for the start of the esophagus).
Special features of linear examination
Examination of an esophageal cancer or a submucosal tumor of the esophagus is not optimal with a linear instrument because the entire lesion does not appear on the same image when it is advanced or withdrawn, and the endoscope handle has to be rotated in addition to the forwards and backwards movement. This is tedious if the tumor is of a considerable length and is near-circumferential, which is almost always the case if the patient is dysphagic. On the other hand, linear examination has the advantage of being able to differentiate better between a celiac or left gastric location of a suspected malignant lymph node located in front of the abdominal aorta, and clearly allows it to be biopsied. It is therefore preferable to perform this after a radial examination if lymph node biopsy is indicated.
The transducer must be pressed against the wall for lymph node examination and separated from the wall by the inflated balloon for examination of the lesion, particularly if it is small. Serosal involvement of the cancer or the originating layer of a submucosal tumor should be interpreted only if the image plane is perpendicular to the lesion, in the craniocaudal direction, i.e. if the muscle layer is clearly visible, longitudinally, above, over and below the lesion, of consistent thickness, and in the axis of the lesion. This technique requires far more training than radial EUS.
Examination of the celiac region
The celiac region is examined by inserting from the cardia, where the aorta should be located longitudinally, then descending 3–6 cm along the vertical lesser curve, along the aorta with small clockwise and anti-clockwise movements of the endoscope handle, since the celiac trunk often takes off laterally from the anterior face of the aorta. After locating the origin of the celiac trunk, follow it to the origin of the left gastric artery (see Fig. 52 ) which can be seen climbing vertically along the stomach then as far as the bifurcation of the hepatic artery and the splenic artery (see Fig. 52 ). The upper margin of the pancreatic body appears 1 cm below this bifurcation (see Fig. 53 ). The celiac lymph nodes are sometimes located in this bifurcation, sometimes along the lateral sides of the celiac trunk, which is examined by turning the endoscope handle clockwise and anti-clockwise in front of its origin. The left gastric lymph nodes are closer to the stomach along the left gastric artery, which is examined by following it upwards while withdrawing the echoendoscope from its origin at the celiac trunk.
Examination of the posterior mediastinum with linear instruments
The lymph node areas of the posterior mediastinum and the celiac and mesenteric region should be examined in patients with cancer of the esophagus and cardia, when assessing bronchogenic cancer or in patients with benign or malignant mediastinal masses.
The examination always begins in the stomach over the celiac region. The left adrenal gland, readily located by turning the endoscope handle clockwise from the celiac trunk, should then be examined. The left lobe of the liver is easy to locate by turning the handle anti-clockwise from the celiac trunk.
The endoscope is then brought up to the cardia (40 cm from the incisors), following the aorta longitudinally. At this point the suprahepatic venous confluence at the inferior vena cava ( Fig. 14A ) and the dome of the liver, which is located around it, can be observed by turning the handle clockwise and anti-clockwise, then climbing along the inferior vena cava as far as the right atrium ( Fig. 14B ). When the right atrium disappears on withdrawal of the endoscope (35 cm from the incisors), the left atrium ( Fig. 14C ) can be examined by making small clockwise or anti-clockwise turns of the handle, and the endoscope is brought up along the central part of the left atrium (the largest part) as far as its upper margin (28–30 cm from the incisors). On withdrawal, the subcarinal region then appears and the screen shows, below the transducer, from top to bottom, the air present in the trachea and carina, the subcarinal region, the right pulmonary artery in cross-section ( Fig. 14D ) and the upper part of the left atrium. Turning the handle clockwise and anti-clockwise then allows all the subcarinal lymph nodes ( Fig. 14E ) to be examined (the right group, which is close to the large azygos vein, the central group between the esophagus and the right pulmonary artery, and the left group near the descending aorta).
With maximum up angulation, withdrawing the endoscope 1–2 cm and turning the handle anti-clockwise, the aortopulmonary window (region IVL) will become visible between the aortic arch, round in section, at the top of the screen, and the left pulmonary artery, round in section, at the bottom of the screen ( Fig. 14F ).
Continuing withdrawal of the endoscope reveals the supraaortic (left paratracheal and para-esophageal) region with the left common carotid artery ( Fig. 14G ) and the left subclavian artery ( Fig. 14H ), then the origin of the left vertebral artery and the left retroclavicular lymph node region, finally, above the left thyroid lobe.
If the handle is turned clockwise from the aortic arch, the trachea, then the supra-azygos region (above the arch of the azygos vein), and if the endoscope is retracted keeping the same image plane, the brachiocephalic trunk will appear followed by its bifurcation into the right subclavian and right carotid artery, the origin of the right vertebral artery, then the right thyroid lobe.
How to examine the stomach
It is advisable to almost always start with a radial instrument. It is far easier and more comprehensive. The linear instrument can be used first only if the examiner has to biopsy a large submucosal tumor suspected of being a GIST. By contrast with conventional teaching, it is advisable to instil water into the stomach only very rarely, because it is usually ineffective and may cause pulmonary aspiration.
Examination of the stomach with a radial instrument
For malignant or suspected malignant tumor disease, the examination begins in the duodenum, as for pancreaticobiliary examination, looking for retropancreatic and interaortocaval metastatic adenopathy, particularly at the base of the posterior segment of the hepatic pedicle. Returning into the bulb allows examination of the preportal (pyloric) hepatic chain. Moving into the stomach allows examination of the left gastric, celiac and cardiac lymph node regions. Each part of the stomach should be examined systematically, the antrum, body and fundus, to be sure you have examined the lymph node areas adjacent to these regions. The liver is the key landmark anteriorly, the pancreas is the key landmark posteriorly, the spleen for the greater curve, and the lesser curve can be readily located at the junction between the posterior and anterior walls ( Fig. 15 ).
The key to success when performing EUS of the gastric wall is to try to obtain a study of the layers of the wall so that they are perpendicular to the ultrasonic beam ( Fig. 1 ). EUS is not possible across the whole circumference of the stomach simultaneously. In other words, once the anomaly to be examined has been located roughly on one wall of the stomach, focus on this anomaly so that the layers of the wall over and below the anomaly, but also at its edges, are clearly individualized. It is only by proceeding in this manner that you can be sure that the EUS abnormalities are real and not due to an ‘oblique image’ which may be misinterpreted (overlapping of several structures creating false images that suggest serosal involvement of a tumor or wrongly attributing the anomaly to a layer other than the one in which it is actually located). Examination of the fundus is sometimes difficult when the lesion in question is small. It is sometimes easier to perform the examination without instillation of water, after aspirating all the air present. It is sometimes necessary to work with the echoendoscope in retroflexion to visualize the anomaly if it is small. Examination of the body of the stomach is easy, and examination of the antrum is equally easy for the horizontal portion. On the other hand, examination of the incisura is more problematic. The best solution is to inflate the balloon immediately upstream of the pylorus, maintaining maximum up angulation, to check that the gallbladder is facing the anterior side, which means that the lesser curve is then at the bottom of the screen and the greater curve at the top. Once this has been confirmed, withdrawal of the echoendoscope, with the balloon inflated and up angulation, usually means that it can remain perpendicular to the lesser curve, whether in the horizontal portion, the incisura itself or the vertical portion immediately above the incisura. Examination of an immediate prepyloric lesion is difficult because it is often impossible to avoid oblique images of the pylorus itself which will give the impression that there is a submucosal tumor in the muscle layer. This is a frequent cause of false positive results for stromal tumors. This type of error obviously occurs only with small tumors, since large tumors are usually clearly visible, regardless of the image plane used.
Left lateral decubitus position.
Use a balloon for the antrum, lesser curve, posterior side and anterior side.
Instil 50–100 cc water into the stomach only if essential to improve visualization of the superficial layers (then raise the patient’s head and chest). To be avoided if the patient is under deep sedation or general anesthesia, or has a hiatus hernia.
Examination of the stomach with a linear instrument
It is advisable to use a linear instrument only to biopsy a submucosal tumor whose exact location has already been determined by UGIE or by a radial examination performed immediately beforehand.
How to examine the pancreaticobiliary region
Essential anatomic knowledge for correctly performing a pancreaticobiliary examination
Familiarity with the celiac and mesenteric anatomy is required:
The celiac trunk takes off from the anterior side of the aorta, 3–4 cm below the cardia. The celiac trunk sometimes takes off to the front perpendicular to the aorta, but it usually runs at an oblique angle to the right and front and sometimes, very rarely, it runs first diagonally to the left before bending to the right. Its first branch is the left gastric artery towards the top; this is not clearly visible in its initial portion in a radial image, although it is very clearly visible on linear imaging. It then splits into the splenic artery and the hepatic artery.
The hepatic artery heads right, usually horizontally, and then becomes the gastroduodenal artery and the hepatic artery proper. The gastroduodenal artery is the key landmark for the anterior part of the pancreatic head. A tumor located to the right of the origin of the gastroduodenal artery can be resected only by Whipple’s pancreaticoduodenectomy, whereas a tumor located to the left of the origin of the gastroduodenal artery can be resected by middle pancreatectomy or by left pancreatectomy. The gastroduodenal artery is visible behind the duodenal bulb. It is therefore examined best through the duodenal bulb. This artery leads into the anterior and superior pancreatico-duodenal artery, which in turn becomes an arterial branch that descends along the second part of the duodenum to the region of the ampulla of Vater. This arterial branch is therefore usually parallel to the path of the common bile duct and Doppler imaging can distinguish the artery path from the bile duct, if the latter is narrow.
The splenic artery, at its origin, may head slightly right before turning left. Its path is almost always downwards initially, before turning left and following a more upwards route to the left. The splenic artery extends along the upper edge of the body-tail of the pancreas, it has a snake-like sinuous path and is visible in radial images in only small portions.
The splenic vein usually runs over the posterior segment of the pancreatic body and tail. It extends horizontally and a long segment of the vein can be examined in a radial imaging. There is usually some pancreatic parenchyma visible, between the stomach and the splenic vein, but the central segment of the pancreatic body and tail is usually below the level of the splenic vein, so that the pancreatic duct which is in the central segment of the pancreatic gland appears horizontally in a transverse radial image, when the splenic vein is no longer visible.
The right hepatic artery, which branches off from the hepatic artery proper, generally crosses the common bile duct below the hilum. It may indent the common hepatic duct, causing an appearance of pseudostenosis on MRCP. This artery, which is often infiltrated in the presence of cholangiocarcinoma of the common hepatic duct, normally takes off from the hepatic artery proper in the middle part of the hepatic pedicle. It may take off early and intersect the portal trunk prematurely, then run along its right edge, parallel to the common bile duct before intersecting it at the top right and entering the hilum of the liver.
In 15% of cases the right hepatic artery takes off from the superior mesenteric artery. It then extends initially into the area known as the retroportal region, when it is visible between the right edge of the portal vein and the common bile duct. The retroportal region is a very important region for assessing the spread of cancers of the pancreatic head, which cause jaundice. This region is located between the posterior side of the portal vein in front, the superior mesenteric artery to the left and the anterior side of the inferior vena cava to the rear.
After crossing the retroportal region, the right hepatic artery, which is a branch of the superior mesenteric artery, intersects the posterior right edge of the portal vein and then extends along the right edge of the portal vein, along the common bile duct (between the portal vein and the common bile duct), before intersecting the common hepatic duct at the top right, and then entering the hilum of the liver.
To summarize, when you see an arterial structure at the right edge of the portal vein, between this and the bile duct, on a radial EUS image that passes through the common bile duct examined longitudinally at the common hepatic duct and the cystic duct-common bile duct junction and through the portal vein (likewise in a linear image), this is the right hepatic artery. If you see the right hepatic artery here, i.e. distinctly under the hilum of the liver, this means that the artery takes off either prematurely from the hepatic artery proper (which is rare), or from the superior mesenteric artery (which is usually the case).
The ampulla of Vater is the extreme right posterior segment of the pancreatic head. The uncinate process is located below and behind the ampulla of Vater, and the posterior segment of the pancreatic head is located above it. If you can see the common bile duct running towards the ampulla of Vater, you are over the posterior segment of the pancreatic head; if the common bile duct disappears into the duodenal wall, you are in the region where the uncinate process begins. This is therefore the lowest and most posterior segment of the pancreatic head.
The common bile duct follows a retropancreatic path, i.e. it is very posterior to the pancreatic head, even its most posterior segment. It terminates in an intrapancreatic path measuring no more than 15 mm in height in front of the duodenal wall. This means that, if necessary, an experienced surgeon can detach the anterior side of the common bile duct from the channel in which it runs in the posterior part of the pancreatic head, with a view to sectioning the bile duct at the point where it enters the pancreatic head. This type of surgery is sometimes performed during liver transplants for primary sclerosing cholangitis to minimize the length of the residual biliary stump and to reduce the subsequent risk of bile duct cancer. It is also performed in order to resect the common bile duct in patients with choledochal cysts.
The cystic duct terminates at the right wall of the hepatic duct to form the common bile duct in 85–90% of cases. In 10% of cases, there is a low insertion of the cystic duct and common bile duct, i.e. located in the retropancreatic segment of the common bile duct.
In 10–15% of cases, the cystic duct intersects the common bile duct, terminating at its left edge. This is why the cystic duct does not terminate in the place where you might expect (at the right edge of the common bile duct) in one in 10 cases, in a radial image. It is therefore important to be aware of this possibility and to try to create ultrasound images which show the intersection of the cystic duct with the bile duct.
The gallbladder has three segments: the fundus, the body, and the left segment which is the infundibulum. The infundibulum is hook-shaped. It is the most frequent site of small stones that have gone undetected during percutaneous ultrasound. The gallbladder fundus is sometimes best examined through the antrum by pushing the echoendoscope with the balloon inflated towards the pylorus. Gallstones are generally located in the fundus of the gallbladder, and are therefore sometimes visible only when the echoendoscope is placed in the antrum, pushing towards the pylorus. The gallbladder may be bilobed, i.e. with a partial septum in the middle segment of the body which separates the gallbladder fundus from the infundibulum. This encourages formation of stones in the gallbladder.
The main pancreatic duct, which is known as Wirsung’s duct in the absence of pancreas divisum, runs along the central segment of the pancreatic gland, i.e. in the middle of the pancreas along the tail, body and neck. In the pancreatic head, however, the main pancreatic duct extends first along the anterior segment of the head, then along the middle of its right segment, and finally along its posterior segment, towards the ampulla of Vater, which is the most posterior segment of the pancreatic head. The main pancreatic duct thus lies in the path of pancreatic cancers that can cause jaundice, as 70% are located in the posterior segment of the pancreatic head. This is why cancer of the pancreatic head causing jaundice is almost always accompanied by dilation of both the bile duct and the pancreatic duct. Paradoxically, this dilation of both ducts sometimes does not occur in cases of tumor of the ampulla of Vater since this may be located purely in the biliary segment of the ampulla, leaving the termination of the main pancreatic duct unaffected. The main pancreatic duct can be visualized through the duodenal bulb using EUS, starting at the pancreatic neck and advancing to the right part of the pancreatic head. From this point on, the duct can sometimes be seen, in 10–15% of cases, terminating horizontally in the upper segment of the pancreatic head, while the common bile duct is still visible in the hepatic pedicle, and the gallbladder is still visible. If you see the pancreatic duct terminating in or running very close to the duodenal wall while the bile duct is still visible in its suprapancreatic course and has not yet begun its retropancreatic path, this is known as a dominant dorsal main pancreatic duct, which in most cases indicates the presence of pancreas divisum. Pancreas divisum may of course be incomplete, i.e. there may be a small passage between this dominant dorsal duct and the main pancreatic duct, which is in the ventral pancreas, but this passage is often extremely narrow and may not be detected by EUS or MRCP. On the other hand, if the main pancreatic duct is followed into the pancreatic head then appears parallel to the bile duct, running towards the ampulla of Vater, this means that the main pancreatic duct that you saw in the upper segment of the pancreatic head, coming from the neck, and that can be followed towards the ampulla of Vater, is the main pancreatic duct (also known as ‘Wirsung’s duct’), and that the ventral and dorsal segments of the pancreatic gland have fused, which in turn indicates that there is no pancreas divisum. A simple way to determine this using EUS is to find the main pancreatic duct in the upper part of the pancreatic head, which is usually bright and echogenic, corresponding to the dorsal pancreas, and then observe the pancreatic duct entering the hypoechoic segment of the pancreatic head, corresponding to the ventral segment from the embryological standpoint. If the pancreatic duct extends from the echogenic segment of the pancreas to the hypoechoic segment of the pancreas, it can be concluded that there is no pancreas divisum.
The pancreatic tail is usually located above the pancreatic body. The pancreas extends diagonally from right to left and bottom to top. In 10–15% of cases, however, the pancreatic tail is lower than the pancreatic body, in which case it is at a distance from the stomach and is not clearly visible with a radial echoendoscope. In this specific case, you cannot be sure whether the whole of the distal end of the pancreatic tail has been examined. This is clearly visible on CT scans. In the vast majority of cases, the pancreatic tail is easily seen close to the posterior side and the greater curve of the stomach, but the pancreatic tail is sometimes remote from the posterior side and the greater curve of the stomach, and it is easy to understand why it is difficult to examine it completely with a radial echoendoscope. In this case, switch to a linear echoendoscope, which allows visualization, in 100% of cases, of the entire pancreatic tail, even in patients in whom it is remote from the stomach.
Liver segments I, II and III are visible via the stomach using a radial instrument. The liver segment that is visible around the gallbladder through the duodenum is a part of segment IV. When the right kidney becomes visible on advancing the echoendoscope into the duodenum, the liver segments in contact with the right kidney are segment V and segment VI. Segment VII, segment VIII and the anterior part of segment IV can never be viewed with a radial instrument.
Radial EUS pancreaticobiliary examination
The vascular structures are the anatomical landmarks for the examination of the pancreaticobiliary region ( Fig. 16 ).
Left lateral decubitus, tilted towards the examination table at an angle of 30–40°.
Use a moderately inflated balloon.
Begin the examination in the stomach 45–50 cm from the incisors, to examine the body and tail region.
After advancing through the pylorus under endoscopic control, proceed from the bulb to the second part of the duodenum by pushing the echoendoscope gently under ultrasound control, turning the handle clockwise if the superior duodenal angle is open, then push the echoendoscope in the long position towards the ampulla of Vater, adding up angulation. Use the ERCP withdrawal maneuver under endoscopic control, from the apex of the bulb if the superior duodenal angle is closed (thin patient), and allow the head of the echoendoscope to fall into the second duodenum, then push the tip over the ampulla of Vater, in the long position, and start the examination at this point.
Examination of the pancreatic head and the common bile duct
There are three ways of examining the head of the pancreas and the common bile duct:
Start in the duodenal bulb, with the handle in the neutral position, and advance the echoendoscope under ultrasound control, turning the handle clockwise (which brings it to the closed position). Proceed from the duodenal bulb to the superior duodenal angle and then add up angulation to bring the echoendoscope in front of the ampulla of Vater. The gallbladder can then be visualized above the bulb, then the common bile duct, the portal vein and the mesenteric-portal vein confluence, followed by the superior mesenteric vein, the posterior segment of the pancreatic head, the main pancreatic duct parallel to the common bile duct and finally the ampulla of Vater, between 9 and 8 o’clock on the duodenal circumference.
Start over the aorta and inferior vena cava viewed in transverse section, in the ‘long’ position ( Fig. 17 ), i.e. with the tip of the echoendoscope pushed immediately below the ampulla of Vater region, with up angulation, and the handle in the neutral position ( Fig. 18A ). The spine ( Fig. 18B ) is to the rear (top of the screen), and the right kidney may be visible to the right of the inferior vena cava (right of the screen). The liver is sometimes to the front (bottom of the screen) if it overlaps extensively. The gallbladder, which is distended in obstructive jaundice, can also be visualized to the front (bottom of the screen) in this plane. A pancreatic segment is sometimes visible in this image, at the bottom left of the screen. This is the lower anterior segment of the pancreatic head and uncinate process. In this transverse section ( Fig. 18B ), the top of the screen corresponds to the back, the bottom corresponds to the front, and the right and left correspond to the right periduodenal and left periduodenal regions, respectively. The mesenteric vessels are often visible (arteries and veins) in a transverse image, to the left of the duodenum.
By withdrawal of the instrument ( Fig. 19 ), with maximum up angulation, and turning the handle anti-clockwise, which advances the tip into the inferior duodenal angle bringing it upright ( Fig. 20 ), you can see in succession at the top of the screen or the top and right: the aorta ( Fig. 21 ), in a longitudinal image, then the superior mesenteric artery, also in a longitudinal image (to the left on the screen), and the left renal vein in a transverse image between the aorta to the rear and the superior mesenteric artery over and to the front. By withdrawing the echoendoscope a little more, turning anti-clockwise, with up angulation, this image is replaced by a image through the inferior vena cava ( Fig. 22 ), which, like the aorta, occupies the top right of the screen, above the duodenum, the superior mesenteric artery being replaced by the superior mesenteric vein and the mesenteric-portal vein confluence. The segment of the pancreatic head adjacent to the duodenum, between the duodenum, inferior vena cava and superior mesenteric vein, corresponds to the uncinate process of the pancreas then to the posterior segment of the pancreatic head when the echoendoscope is retracted above the ampulla of Vater region. This region is located by the termination of the bile and pancreatic ducts but also by the junction between the two echogenically different regions of the pancreatic head ( Fig. 23 ), present in 75% of patients. These are the hypoechoic right posterior juxta-duodenal area corresponding to the ventral pancreas, and the more echogenic left anterior juxta-mesenteric region corresponding to the dorsal pancreas.
The secret of pancreaticobiliary examination is, while continuing to withdraw the endoscope, to obtain a long view of the mesenteric-portal vein confluence and the common bile duct ( Figs 24, 25 ), which is the non-vascular ductal structure located closest to the duodenal wall. If you obtain an image lengthwise through the common bile duct and the mesenteric-portal vein confluence, what appears on the left of the screen is in fact at the front left, what is on the right of the screen is at the back left, what is at the top corresponds to the hepatic hilum and the liver, and what is at the bottom corresponds to the ampulla of Vater region. The segment of the pancreas between the duodenum and the superior mesenteric vein and the mesenteric-portal vein confluence is the posterior segment of the head.
The ampulla of Vater region can be examined in several ways: the simplest is to push the endoscope gently, following the common bile duct, once it has been brought into vertical view during the initial withdrawal of the instrument ( Fig. 26 ). When trying to follow the common bile duct, turn the echoendoscope handle gently clockwise from the open position to the neutral position while pushing the instrument. Once you can see the bile duct close to the duodenal wall ( Figs 27, 28 ) slight up angulation should be added which causes the bile duct to disappear and the terminal main pancreatic duct to appear ( Fig. 29 ). The ampulla of Vater is then visible between 8 and 9 o’clock in contact with the balloon ( Figs 28, 30, 31 ). An important point to note is that the ampulla is not satisfactorily visible until the bile duct disappears into the duodenal wall.
There is another way of visualizing the ampulla of Vater, but it is fairly difficult because the echoendoscope tends to withdraw rather too quickly during the maneuver. It involves starting from the long position with the handle in the neutral position and withdrawing the echoendoscope with up angulation, turning the handle anti-clockwise, or angulation to the left, which amounts to the same. After visualizing the superior mesenteric vessels in longitudinal section, at the point when the mesenteric vein appears on the screen ( Fig. 22 ), the termination of the main pancreatic duct is usually visible in contact with the duodenal wall ( Fig. 29 ), which means that the ampulla of Vater is exactly over the transducer. Stop withdrawing and advance again slightly so that you can see the last cm of the pancreatic duct along with its penetration point in the duodenal wall, which is then an indication of the presence of the ampulla of Vater between 8 and 9 o’clock on the duodenal circumference ( Figs 30, 31 ).
The third way of examining the pancreatic head and the common bile duct is by specific withdrawal. Unlike the withdrawal described previously ( classic withdrawal), specific withdrawal starts from the long position, with maximum up angulation of the echoendoscope and above all maximum angulation to the right, turning the echoendoscope handle clockwise towards the closed position, i.e. by pressing the endoscope against the top right part ( Fig. 32A ) of the examiner’s chest, withdrawing the echoendoscope in this way will place it in the short position. This is the same maneuver that is carried out with a duodenoscope to place it in the short position, but in this case the maneuver is started from a long position. You will see the aorta first of all, followed by the inferior vena cava at the bottom left of the screen, then the junction between the two echogenically different regions of the pancreatic head (ventral and dorsal) between 5 and 6 o’clock and the main pancreatic duct ( Fig. 32B ) at about 6 o’clock, which means that the ampulla of Vater is visible at this point, if you stop withdrawal and push the echoendoscope again slightly. The ampulla of Vater appears as a small swelling ( Fig. 32C ) in the duodenal wall, surrounded on all sides by a little submucosa and separated from the pancreatic head by a hypoechoic border corresponding to the muscle layer of the ampulla of Vater ( Fig. 32D ). This is the best way of examining tumors of the ampulla of Vater and determining whether the submucosa has been infiltrated. This is also the best way of examining the uncinate process of the pancreas and the last 2 cm of the common bile duct and the main pancreatic duct.
Examination of the gallbladder. The gallbladder can be examined after entering the bulb by inflating the balloon and pushing the transducer towards the superior duodenal angle, handle in the neutral position. The gallbladder is then visible above the balloon ( Fig. 33 ); it disappears as you press on the apex of the bulb and the neck is the last part of the gallbladder visible. If you continue pushing, the bile duct and portal vein then become visible in the left half of the screen ( Fig. 34 ).
If the superior duodenal angle is compliant (rarely the case in slim patients under 40, or in very thin patients of any age), the bile duct can be followed ( Fig. 35 ) to the ampulla of Vater, advancing the endoscope by turning the handle clockwise, with neutral angulation then adding up angulation.
Large diverticula in the medial duodenal wall hinder the examination of the pancreatic head, the ampulla of Vater region and the terminal common bile duct. Instillation of water into the second part of the duodenum usually allows the diverticulum to be filled temporarily and its presence confirmed. If there is no fluid in the diverticulum, it appears as hyperechoic harmonic air gap between the transducer and the pancreatic head, over the region where the pancreatic duct and the common bile duct terminate.
Pneumobilia also hinders the examination of the common bile duct. If it is related to previous endoscopic sphincterotomy, it is usually possible to visualize the bile duct termination by instilling water into the second part of the duodenum, over the ampulla of Vater region. This procedure is brief but usually allows a distinction to be made between residual stones and air in the lower common bile duct. Air remains pressed against the duodenal side of the common bile duct, whereas stones tend to sink against the opposite or pancreatic side of the common bile duct. The common bile duct is usually invisible in the hepatic pedicle in patients with choledochoduodenal anastomosis, despite the instillation of water through the anastomosis.
Examination of the common hepatic duct. The upper part of the common bile duct, i.e. the common hepatic duct and the biliary confluence, can be examined if the diameter of the duct is 5 mm or more. There are two complementary ways, which means that they are rarely both effective in the same patient and depend on his/her specific anatomy.
The simplest way is to start from a neutral handle position, in the duodenal bulb, and advance the echoendoscope, keeping the gallbladder or liver above the balloon and observing the appearance of the common bile duct. At this point, rather than turning the handle clockwise to advance to the second part of the duodenum, turn the handle anti-clockwise to the open position and push the instrument against the superior duodenal angle. You can then see the bile duct running toward the liver: this is the common hepatic duct ( Fig. 36 ) and the superior biliary confluence, often intersected at this point by the right hepatic artery.
If this method is ineffective, you can push the echoendoscope to the long position in the second part of the duodenum and carry out specific withdrawal ( Fig. 32 ). Once the ampulla of Vater has been visualized at 6 o’clock, release right angulation and partially release up angulation, and continue withdrawal of the echoendoscope, with the handle in the closed position.
The common bile duct appears horizontal under the duodenum ( Figs 37A, 37B ). The cystic duct joins the common bile duct from below if you continue withdrawal very gently by adjusting the path of the common hepatic duct, keeping it horizontal by means of up angulation under the duodenum, aiming at the liver which is on the left of the screen. The vessel in this image, which is parallel to the common bile duct visible below it, is the inferior vena cava.
This also allows examination of the gallbladder ( Fig. 38 ), which is to the left of the screen between the liver and the duodenum, turning the handle anti-clockwise from the neutral position and adding up angulation. The gallbladder fundus is at the top of the screen in this image, and the neck level with the balloon with its characteristic hook shape. The cystic duct can be followed from the gallbladder neck to the hepatic duct.
Examination of the anterior side of the pancreatic head and neck. The following image, continuing to withdraw the instrument, reveals the portal vein in a transverse plane in the place of the common bile duct, under the balloon, with the hepatic artery in a transverse image extending in front and above it, almost in contact with the bulb wall ( Fig. 39 ).
This view, which visualizes the portal vein below the transducer ( Fig. 39 ), shows the anterior and superior segment of the pancreatic head between the bulb wall and the anterior side of the splenoportal vein confluence. At this point there is usually a bifurcation between the hepatic artery and the gastroduodenal artery, which can be followed to the rear of the bulb wall (i.e. below the bulb wall on the screen) by making back and forth movements advancing then withdrawing the endoscope, with up angulation, handle in the closed position ( Figs 40, 41 ).
Examination of the pancreatic neck and body
If you continue progressive withdrawal of the echoendoscope, with the balloon very inflated, into the bulb, inverting the pylorus, you will see the pancreatic neck between the pylorus and the anterior side of the splenoportal confluence, below and to the right of the balloon. The landmark which indicates that you are opposite the neck is the superior mesenteric artery which is then visualized below the mesenteric-portal vein confluence ( Figs 42, 43 ), in a transverse image. The main pancreatic duct in the neck is visible between the duodenal wall and the portal confluence.
Entering the stomach, continuing to retract the instrument, with the handle in the neutral position and up angulation, usually positions the instrument in the middle of the gastric body (between 45 and 50 cm from the incisors), over the pancreatic body ( Figs 44, 45 ), with the handle in the neutral position. If you angulate to the right and slightly down, the echoendoscope is pressed against the posterior side of the stomach, which usually allows the left portion of the pancreatic body and tail to be examined, along with the splenic vein ( Fig. 46 ). If you angulate up, this usually places the echoendoscope along the vertical part of the lesser curve, and this allows the right part of the pancreatic body to be examined at its junction with the neck ( Fig. 47 ).
Changing from one of these positions to the other is usually done by slightly withdrawing the echoendoscope 1–2 cm to examine the left side of the pancreatic body and tail ( Figs 48, 49A,B ) and slightly advancing the endoscope 2 cm to visualize the right segment of the pancreatic body and neck ( Fig. 49C ). Apply slight up or neutral angulation when descending to the neck, and neutral or slight down and right angulation when withdrawing the echoendoscope to examine the pancreatic tail.
An important point is that it is as easy to examine the whole of the neck, body and tail, including the angle of the main pancreatic duct ( Fig. 49C ), through the stomach in women (shorter stomach) as it is difficult to visualize the neck and the junction between the neck and the head through the stomach in men. The junction between the neck and the head can thus be visualized (50 cm from the incisors) under the transducer through the bulb ( Fig. 42 ), with the balloon very inflated pulling on the pylorus, with maximum up angulation, and with the handle in the closed position.
The celiac region can be examined immediately above the neck by withdrawing the instrument 1 cm, with maximum up angulation, and the handle in the neutral position ( Fig 50A,B ). An alternative method of examining the celiac region is to follow the aorta from the cardia, descending along the lesser gastric curve ( Fig. 50C ).