16 Endoscopic Retrograde Cholangiopancreatography
Christine Boumitri, Nikhil A. Kumta, and Michel Kahaleh
Endoscopic retrograde cholangiopancreatography (ERCP) has reshaped the management of biliary and pancreatic disease since its introduction in 1968. From a diagnostic tool to a therapeutic tool with expanding use and indications, ERCP continues to be an innovative and exceptional technique with continuous improvements to provide the safest and most effective procedures. While its use as a diagnostic tool is falling out of favor with advances in noninvasive imaging, its therapeutic applications continue to expand for biliary and pancreatic strictures management, stone extraction, and biliary leaks. This procedure has proven to be safe in the pediatric and pregnant population. Performance in high-volume centers by experienced endoscopists is essential with increasing demand for complex cases, which raises the question of training and credentialing.
16.2 Overview of Procedure
The first attempt to cannulate the ampulla of Vater was in 1968 by a group of surgeons in the United States. 1 In 1969, Dr. Itaru Oi presented the first endoscopic cholangiopancreatography (ECPG) at an international meeting and was considered one of the pioneers along with Dr. Kazuei Ogoshi from Japan. 2 , 3 ERCP started to gain success in the early 1970s. Soon after, therapeutic applications of ERCP were developed starting with the first reported sphincterotomy in 1974 by Dr. Kawai in Japan and Dr. Classen in Germany followed by the first biliary stenting in 1979 by Dr. Soehendra. 4 , 5 , 6 Over the last four decades ERCP has shifted from being a diagnostic tool to being used almost exclusively as a therapeutic tool especially with the presence of other diagnostic tools such as magnetic resonance cholangiopancreatography (MRCP), and endoscopic ultrasound (EUS).
16.3 General Diagnostic Techniques
With advances in imaging modalities of the biliary tree and pancreas including computed tomography (CT) scan and magnetic resonance imaging (MRI), the use of ERCP as a diagnostic tool has significantly decreased except for certain instances such as sphincter of Oddi manometry. Regardless of the final intent of the procedure, biliary cannulation remains the first and most important step of all ERCPs.
16.3.1 Biliary Cannulation
The first step starts by establishing the duodenal position to achieve an “en face” position with the major papilla. This can be achieved by advancing the endoscope 2 to 3 cm after reaching the second part of the duodenum with counterclockwise torque. The right left wheel is then turned right and locked followed by clockwise rotation of the shaft with upper deflection of the big wheel. Another technique is to advance the tip of the endoscope to the distal second part of the duodenum and then repeat the same steps mentioned above. 7 Once the duodenal position is achieved, biliary cannulation is attempted. Selective biliary cannulation remains one of the most difficult aspects of the procedure with failed cannulation occurring in up to 20% of cases outside of high-volume expert centers. 8 It is important to know that repetitive and prolonged cannulation increase the risk of post-ERCP pancreatitis (PEP). Cannulation can be achieved with either catheters or sphincterotomes. Most endoscopists use sphincterotomes for biliary cannulation since diagnostic ERCP has fallen out of favor and most procedures are performed with a therapeutic intent. Contrast opacification of the biliary tree is a long-established technique but is being used less due to the increased risk of PEP with inadvertent contrast filling of the pancreatic duct (PD). Wire-guided cannulation is becoming the preferred method of cannulation. This could be achieved by either direct access with the sphincterotome (ST) or by advancing the ST 2 to 3 mm beyond the luminal aspect of the papilla, then gently advancing the guidewire, or the “wire lead” technique where the wire acts as an introducer especially in situation where the papilla is small. Cannulation can fail in certain instances and is considered difficult after 5 minutes of attempting common bile duct (CBD) cannulation, five failed attempts or after more than two inadvertent pancreatic duct cannulation. 9 , 10 Multiple risk factors have been associated with failed cannulation such as Billroth I and II surgeries, Roux-en-Y gastrojejunostomy, hepaticojejunostomy, Whipple surgery, gastric outlet obstruction, or duodenal narrowing and malignant biliary tract obstructions such as periampullary tumors distorting the ampulla of Vater. 11 , 12 , 13 , 14 , 15 , 16 The literature is not clear whether periampullary diverticulum is a risk for failed cannulation or not. Boix et al reported that cannulation is more difficult in type 1 diverticula (where the papilla is inside the diverticulum). 12 , 17 , 18 , 19
In the instance of failed or difficult access, the endoscopist should consider alternative ways of cannulation. If repetitive attempts of biliary cannulation result in access to PD, a PD stent can be placed thus decreasing the chance of PEP and facilitating access into the bile duct. Another option would be to use the dual-wire technique in which case the wire is left in the PD and sphincterotome is withdrawn from the papilla and loaded with a second guidewire for biliary cannulation. This technique can be used in patients with pancreas divisum. Access sphincterotomy describes techniques where cutting is performed prior to cannulation in order to facilitate access into the bile duct, another term is needle–knife sphincterotomy or precut sphincterotomy.
16.3.2 Sphincter of Oddi Manometry
Sphincter of Oddi manometry (SOM) is the gold standard to study pressure dynamics of the sphincter of Oddi in patients with high clinical suspicion for sphincter of Oddi dysfunction (SOD). According to the Milwaukee classification, there are three types of SOD. A recent update of Rome criteria (Rome IV) for sphincter of Oddi disorders considered that the classification of SOD into three types no longer applies since patients with SOD type I (dilated bile duct and elevated liver enzymes) have organic stenosis and benefit from sphicterotomy. 20 On the other hand, patients with SOD type II (dilated bile duct or elevated liver enzymes) should be labeled as suspected functional biliary sphincter disorder (FBSD). 20 SOM can be especially helpful in establishing the diagnosis of patients with type II and III SOD and sphincterotomy should be considered based on manometry results. 21 , 22 However, the EPISOD trial revealed that patients with SOD type III do not respond to sphincter ablation better than sham intervention and only patients with type II SOD would benefit from manometry directed sphincterotomy. 23 , 24 , 25 This procedure is technically challenging and requires high expertise in a center that is known to provide it. There is variation in pressure measurements depending on catheter size, probe position, and point of time when spasm is captured. 26 It is also associated with high risk of pancreatitis up to 9%. 27 The patient should be well sedated during the procedure and any drugs that might stimulate (narcotics, cholinergics) or relax (nitrates, calcium channel blockers, glucagon) the sphincter should be avoided 8 to 12 hours before the procedure and intraprocedure. Opioids should be avoided due to risk of inducing SO spasms. 28 , 29 , 30 , 31 Meperidine at a dose less than or equal to ≤ 1 mg/kg, ketamine, droperidol (discontinued in the united states), and propofol use have not been shown to significantly affect the basal pressure of the sphincter. 32 , 33 , 34 , 35 , 36 Two types of catheters are available for SOM: water perfused and solid state. 37 The procedure starts by passing the catheter along the working channel of the duodenoscope; once the duodenum is reached, a baseline or zero duodenal pressure is measured and recorded before cannulation. 22 This is followed by cannulation of the biliary or pancreatic duct. The need to measure both pancreatic and biliary sphincter remains controversial. 38 Cannulation can be achieved with the manometry catheter or with the aid of a 0.018 guidewire. It is reasonable to perform ERCP prior to manometry to make sure that there is no stone or obstruction that might obviate manometry. Contrast injection has not been shown to affect manometry results. 39 Once cannulation is obtained, measurement of ductal pressure is noted. This is obtained by the slow flow of pressurized water from an external pump to the sphincter of Oddi through the catheter. The catheter is then withdrawn at 1 to 2-mm intervals by station pull-through technique pausing for 60 to 90 seconds once the area of the sphincter is reached. 40 A basal sphincter pressure of greater than 40 mm Hg is used to diagnose SOD. 41 , 42 , 43 This is the calculated mean pressure readings from three pull-throughs. 44 Patients with SOD type I (evidence of SO obstruction) are treated with sphincterotomy without manometry. 43 Patients with type II SOD may benefit from sphincterotomy if manometry reveals increased basal pressure. This was the case in three small-randomized studies, which showed that sphincterotomy was more effective than a sham procedure in these patients. 24 , 25 , 45
16.4 General Therapeutic Techniques
The innovations in technologies and equipment led to the expansion of the therapeutic applications of ERCP. A brief review of the most common therapeutic techniques is described below. Among others, sphincterotomy, endoscopic papillary balloon dilation, stone extraction, and stent insertion are considered an integral part of therapeutic ERCP that advanced endoscopists should master.
16.4.1 Biliary Sphincterotomy
Having the ampulla between the 11 and 1 o’clock positions facilitates deep cannulation, after which, the sphincterotome can be withdrawn to the desired incision length. The sphincterotomy should be performed in the longitudinal axis and never be continued beyond the junction of the intramural segment of the CBD and the duodenal wall. There is significant variation in choice of electrosurgical current used (cutting current, blended current, “ENDO CUT” mode). Possible complications include bleeding, pancreatitis, as well as retroperitoneal perforation resulting from a fast and uncontrolled “zipper” cut. 46 , 47 The most common indications for biliary sphincterotomy are CBD stones with or without cholangitis, facilitation of biliary stent placement for malignant or benign biliary obstruction, benign papillary stenosis, SOD types I and II when manometry reveals high basal pressure, biliary leaks, and others. 48 Pancreatic sphincterotomy (PS) is usually performed for pancreatic SOD, biliary SOD that does not respond to treatment with biliary sphincterotomy, chronic pancreatitis with papillary stenosis or stricture, and pancreas divisum. PS can also be used to facilitate other biliary pancreatic intervention such as transpapillary drainage of pancreatic pseudocysts, chronic pancreatitis with ductal stones treated with pancreatic stents, and/or stone removal and malignant strictures. 49
16.4.2 Endoscopic Papillary Balloon Dilation
Endoscopic papillary balloon dilation (EPBD) is an alternative to sphincterotomy, first introduced in 1983. 50 It carries less risk of perforation and bleeding compared with sphincterotomy. Reports of increased risk of PEP with the use of EPBD led to a decrease in use, though in the 1990s it regained popularity with multiple reports showing its safety and noninferiority to sphincterotomy. 51 , 52 , 53 Ideal patients to be selected for EPBD as a substitute to sphincterotomy are those with fewer than or equal to three stones, stone less than 10 mm in diameter, age less than 50, impaired hemostasis, CBD less than 12 mm, no previous or ongoing pancreatitis. 54 , 55 , 56 Endoscopic papillary large balloon dilation can also be used as adjunctive tool with sphincterotomy for large complicated CBD stones, where a small endoscopic sphincterotomy (ES) can help direct the direction of sphincter of Oddi dilation and prevent postprocedure pancreatitis by decreasing periampullary edema. In addition, the combination of a small ES with EPBD reduces the need for mechanical lithotripsy when compared to ES alone. 57 After cannulation, a 0.025- or 0.035-in guidewire is inserted into the bile duct followed by removal of the cannula and insertion of a balloon-tipped catheter (CRE Wire-Guided Balloon, Boston Scientific, Natick, Massachusetts) over the guidewire. Usually, two-thirds of the balloon is inside the distal CBD and one-third is outside the papillary orifice. The balloon is then inflated with diluted contrast until the waist disappears. The dilation is maintained for 15 to 30 seconds. Different dilator balloons sizes are also available depending on the size of the bile duct. When dilating strictures, the endoscopist should be cautious for an increased risk of perforation.
16.4.3 Stone Extraction
Stones that are less than 1 cm will pass spontaneously after performing sphincterotomy and stones larger than 2 cm will most likely require additional fragmentation either mechanically using baskets or with intraductal electrohydraulic or laser lithotripsy and, rarely, extracorporeal shock wave lithotripsy (ESWL). 58 Sphincterotomy should be large enough to allow passage of the stone, otherwise impacted stones may result. Extraction can be achieved using retrieval balloon catheter or Dormia basket to sweep out the stone; mechanical lithotripsy (BML-V237QR-30 or BML-V242 QR-30, Olympus Medical Systems, Tokyo) can be used to fragment large stones. In complicated cases where stone extraction cannot be achieved, temporary biliary stenting to achieve biliary drainage and prevent sepsis and cholangitis should be performed while medical therapy with oral dissolution agents are used to decrease stone size and facilitate endoscopic extraction. 59 , 60 If stones are unable to be visualized, then the endoscopist has to change scope position to the long position to make sure no stones are hidden behind the endoscope. Small stones can be missed when a large amount of dense contrast is injected into a dilated duct. 61
16.4.4 Biliary Stenting
Indications for biliary stenting include treatment of obstructive jaundice from benign causes, such as biliary stones or bile leaks, and malignant etiologies. Both plastic and metallic stents can be used. Plastic stents are more commonly used for benign strictures. With the emergence of metallic stents, their use for malignant strictures has decreased but are still considered and used for palliation in patients with distal malignant biliary tumors when the expected survival is 3 to 6 months. 62 They are usually formed of Teflon, polyethylene, or polyurethane, and come in different configurations (straight, single pigtail, or double pigtails), lengths, and width. They tend to be obstructed by food debris and biofilm and usually require exchange within 3 to 6 months. Stents less than 8.5 F are usually advanced over the guidewire using a pushing catheter. Stents greater than 8.5 F have an inner guiding catheter that passes over the guidewire. When stenting a distal malignant biliary stricture, a 10-F plastic stent is preferable to a 7 F due to prolonged patency. Sphincterotomy or balloon dilation of the stricture is not necessary; however, this is not the case when dealing with hilar strictures or when placing more than one biliary stent.
Self-expandable metallic stents (SEMS) can be uncovered (uSEMS), partially covered (pcSEMS), or totally covered (cSEMS). These were introduced after plastic stents and are primarily used for palliation and drainage of malignant obstruction secondary to surgically unresectable tumors. These offer longer patency due to a larger diameter. 63 , 64 , 65 , 66 uSEMS are associated with higher occlusion rate due to tumor ingrowth, this problem is surpassed by using cSEMS, however, the latter is associated with higher migration rate. pcSEMS were created to overcome the issues faced with uncovered and fully covered metallic stents. No benefit to survival or morbidity was observed when comparing uSEMS to cSEMS. 67 , 68 Innovative mechanisms to decrease the rate of duodenal biliary reflux and metallic stent obstruction has led to the creation of antireflux valve metal stent (ARVMS) with preliminary results revealing superior duration of patency compared to cSEMS. 69 There is an increased use of SEMS for benign biliary conditions such as strictures, leaks, and postsphincterotomy bleeding. 70 , 71 , 72 While placing SEMS, it is crucial to obtain an adequate cholangiogram prior to deploying the stent that will help the endoscopist in assessing the location and length of the stricture and guide on the choice of stent to be used. Once the endoscopist has made the decision with the type of stent to be used, deployment of the stent should be performed under endoscopic and fluoroscopic guidance. The stent is passed over the guidewire and advanced to the stricture level; the introducer catheter is passed over it. Fluoroscopic images are obtained to give an approxima tion of the postdeployment proximal and distal ends of the SEMS.
16.5 Accessory Devices and Techniques
Duodenovideoscopes are side-viewing endoscopes that are designed for both diagnostic and therapeutic ERCP. They are equipped with an elevator that allows the manipulation of the accessories introduced in the working channel. The side-viewing endoscopes are available for the pediatric and adult populations. The adult duodenoscope is available from three different manufacturers (Olympus, Pentax, and Fujinon) (▶Fig. 16.1). The insertion tube diameter can range between 10.8- and 12.1-mm diameter with a biopsy channel diameter between 3.2 and 4.8 mm according to the manufacturer. 73 The pediatric duodenoscopes have an outer diameter of 7.5 mm and an accessory channel of 2 mm. The use of the latter is limited though due to the paucity of accessories available for the smaller working channel especially when performing therapeutic ERCPs. In a recent review, Troendle et al suggested that pediatric duodenoscope should be the instrument of choice in patients less than 10 kg (22 lb), whereas adult duodenoscope could be safely used in patients greater than 10 kg. 74 We suggest that the use of the duodenoscope be at the discretion of the endoscopist based on a case-by-case basis and taking into account the patient’s age and weight, nature of the ERCP procedure, and anticipated accessory channel equipment to be used.