Endoscopic Ultrasound-Guided Fine Needle Aspiration and Biopsy

Melinda C. Rogers, MD

V. Raman Muthusamy, MD

Endoscopic ultrasound (EUS) was first introduced in 1980 as a transluminal imaging modality and has evolved to include therapeutic interventions such as fluid sampling and tissue acquisition of lesions in and adjacent to the gastrointestinal tract. Tissue acquisition has advanced from fine needle aspiration (FNA) for cytology to include fine needle biopsy (FNB) for histology with the development of new tools that allow for the capture of a piece of core tissue with preserved architecture and morphology. These techniques reliably give the ability to sample lesions that conventional cross-sectional imaging (computed tomography or magnetic resonance imaging) cannot identify due to their small size and may be inaccessible by percutaneous techniques. Additionally EUS can achieve a tissue diagnosis less invasively than procedures such as mediastinoscopy, diagnostic laparoscopy, laparotomy, and thoracotomy. It is important to note that the sensitivity and specificity are practitioner dependent and competency requires focused training to achieve technical mastery of this skill set. Additional factors, such as the presence of on-site cytopathology and the specific characteristics of the lesion, can influence the accuracy of EUS-guided tissue acquisition. EUS with FNA/FNB has become the standard of care for many conditions of the gastrointestinal tract and adjacent structures due to its high diagnostic accuracy as well as the minimal invasiveness and safety of this procedure.

INDICATIONS

Endosonography-guided tissue acquisition can be safely performed from the esophagus, stomach, duodenum, and rectosigmoid colon. Indications for EUS include the following:

1. Primary diagnosis of lesions within the gastrointestinal tract (esophagus, stomach, duodenum, and rectosigmoid), adjacent
organs (pancreas, liver, kidneys, adrenals, spleen, gallbladder, bile duct), and spaces (mediastinal, pleural, peritoneal, and pelvic)
2. Staging of metastatic disease
3. Evaluation of unexplained lymphadenopathy in the mediastinum, abdomen, or retroperitoneum
4. Sampling of peritoneal or pleural fluid
5. Liver biopsy for unexplained liver test abnormalities or presence of fibrosis
6. Prior nondiagnostic biopsy

RELATIVE CONTRAINDICATIONS

1. Altered anatomy prohibiting access
2. Vessel present in between the needle and target lesion
3. Mediastinal cystic lesions
4. Lymph node or other lesion biopsy in which the primary tumor is within the needle path
5. Small lesions (<5 mm)
6. Active use of antithrombotic or anticoagulant medications (with the exception of low-dose aspirin and nonsteroidal anti-inflammatories).¹ In select cases, the benefit of performing FNA with a 25 G needle may outweigh the risk of bleeding in select patients requiring the use of antithrombotic or anticoagulant medications

ABSOLUTE CONTRAINDICATIONS

1. Uncorrectable bleeding diathesis (international normalized ratio [INR] >1.5, platelets <50,000)
2. Unacceptable sedation risk

PREPARATION

EUS with FNA can be performed in both the ambulatory and inpatient settings. Initial patient evaluation should include a history, physical examination, and review of the pertinent medical records, including available imaging. Informed consent must be obtained and should include a thorough discussion of the indication, risks, benefits, alternatives, and timing of the EUS procedure. Consent must also be obtained for the administration of the appropriate level of sedation. It is our practice to perform most diagnostic EUS procedures with monitored anesthesia care; however, general anesthesia may be most appropriate if the patient is at risk for sedation-related complications, airway obstruction, aspiration, or in the setting of combined procedures, such as EUS and endoscopic retrograde cholangiopancreatography (ERCP).

Patients are required to fast for a stated period of time prior to EUS of the upper GI tract. This practice is to allow for sufficient gastric emptying to occur before the procedure so as to reduce the risk of aspiration and also to allow for adequate endoscopic visualization. There is currently no universally accepted standard for the time frame that a patient must be fasting prior to the procedure. Our practice follows the American Society of Anesthesiologists (ASA) guidelines, which indicate that patients should be fasting a minimum of 2 hours after ingestion of clear liquids and 6 hours after ingestion of a light meal before sedation is administered.² Patients with a documented history of delayed gastric emptying may require longer periods of fasting. For patients undergoing EUS of the lower GI tract, a full colonoscopy prep is also recommended. In select cases of distal lesions (rectal) or the inability to tolerate an oral preparation, a series of enemas may be administered to cleanse the distal colon.

EUS with FNA has a higher risk of procedure-related bleeding compared with diagnostic upper endoscopy.¹ As such, patients on anticoagulants and antithrombotic medications should be instructed to discontinue these medications at an appropriate interval (depending on the medication) prior to their procedure.³ In certain patients with high-risk cardiac and/or hypercoagulable conditions, the risk of discontinuing these medications may outweigh the risk of bleeding. In such a situation, using the smallest FNA needle (25 G) with a limited number of passes and avoidance of suction would seem appropriate.

The risk of bacteremia related to EUS with FNA of solid lesions of the upper GI tract is low (0% to 5.8%) and comparable to that of diagnostic endoscopy.⁴,⁵,⁶ Similarly, rates of bacteremia or clinically significant infectious complication associated with aspiration of rectal or perirectal lesions are low, and routine antibiotic prophylaxis for these indications is not recommended. The risk of infectious complication related to aspiration of pancreatic and peripancreatic cysts varies in published reports, ranging from 0.6% to 14% but is generally considered to be very low.⁷,⁸ In one large retrospective study, there was no difference in infectious complications after EUS-FNA of cystic lesions with or without antibiotic prophylaxis. Additionally, there were reports of adverse events related to antibiotic usage, including allergic reaction and Clostridium difficile diarrhea.⁹ There are currently no prospective studies examining the effectiveness of periprocedural antibiotics in reducing procedure-related infectious complications. It is the recommendation of the American Society for Gastrointestinal Endoscopy (ASGE) to administer prophylactic antibiotics before and for 3 to 5 days after aspiration of pancreatic and peripancreatic
cysts.¹⁰ Additionally, there are limited data available on the risk of infectious complication associated with aspiration of fluid compartments. It is reasonable to consider periprocedural antibiotics when aspirating fluid compartments, such as ascites, especially in patients with cirrhosis so as to reduce the risk of spontaneous bacterial peritonitis. There is a significant risk of infectious complications related to aspiration of mediastinal cysts with reports of mediastinitis even with the use of periprophylaxis. Thus, we would advise avoiding aspiration of mediastinal cysts.

EQUIPMENT

EUS is currently available in two primary imaging planes; radial and curved linear array. EUS with FNA and/or FNB is performed using a linear-array echoendoscope since the imaging transducer is oriented parallel to the long axis of the endoscope, allowing for clear visualization of the biopsy needle as it exits the therapeutic channel of the echoendoscope and into the target lesion in real time (Fig. 30.1). Doppler and/or power flow imaging-equipped echoendoscopes allow for easy identification of vascular structures.

EUS-FNA needles are available in multiple sizes including a 19, 22, and 25 gauge. Most aspiration needles have a handle assembly for the controlled advancement of the needle, an attachment for a vacuum syringe, a protective sheath, a stylet to avoid damage
to the working channel, and a hollow needle in one of the above sizes. The primary aim of FNA is to acquire an adequate tissue sample with minimal number of passes while avoiding injury to the surrounding tissue. Studies comparing 22 G and 25 G aspiration needles for histology did not show a significant difference between the two, while several studies and a meta-analysis comparing 22 G and 25 G aspiration needles for cytology from solid pancreatic lesions show a higher diagnostic accuracy with the 25 G needle.

FIG. 30.1 Echogenic needle tip exiting the working channel of a curved linear-array echoendoscope (Boston Scientific Expect needle). (Permission for use granted by Boston Scientific Corporation.)

FNB needles also come in a 19-, 22-, and 25-gauge size (Fig. 30.2). The bevel of the needle is variably shaped depending on the manufacturer to allow for shearing of the target lesion in order to acquire a histologic sample (Figs. 30.3 and 30.4). FNB needles are a relatively new development in the field and an area of ongoing clinical research. Initial studies of core biopsy needles failed to show a significant difference with regard to sample adequacy, diagnostic accuracy, or acquisition of a histologic core tissue sample compared to a standard aspiration needles.¹¹ Some studies have shown an improved sample cellularity and fewer passes required to obtain an adequate sample when using a core biopsy needle. A recent study looking at core biopsy of multiple types of solid lesions showed a diagnostic adequacy of 98.5% with a mean of three needle passes¹² through the target lesion. A prospective randomized controlled trial comparing FNA and FNB in patients referred for EUS with tissue acquisition showed significantly higher specimen adequacy with FNB
needles for all solid lesions. There was no difference in diagnostic yield in the two groups for pancreatic masses, and primary advantage observed with FNB needles was for subepithelial lesions and lymphadenopathy.¹³ Importantly, these studies have not demonstrated an increased rate of complications with the use of core biopsy needles.

Only gold members can continue reading. Log In or Register to continue