Endoscopic Retrograde Cholangiopancreatography for Stone Burden in the Bile and Pancreatic Ducts

Stones in biliary and pancreatic ducts are entities that plague hundreds of thousands of patients worldwide every year. Symptoms can be mild (pain) to life threatening (cholangitis, severe acute pancreatitis). In the last few decades, management of these stones has transitioned from exclusively surgical to now predominantly endoscopic techniques. This article reviews the evolution of endoscopic techniques used in the management of stones in the common bile duct and pancreatic duct.

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Stones in the bile duct and pancreatic duct are entities that plague hundreds of thousands of patients worldwide every year.
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Symptoms can be mild (pain) to life threatening (cholangitis, severe acute pancreatitis). In the last few decades, management of these stones has transitioned from exclusively surgical to now predominantly endoscopic techniques.
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This article reviews the evolution of endoscopic techniques used in the management of stones in the common bile duct and pancreatic duct.

Key Points

Bile duct stones

Conventional Endoscopic Therapies

The management of common bile duct (CBD) stones was predominantly surgical for almost 100 years. The introduction of endoscopic sphincterotomy (ES) by Classen and Demling and Kawai and colleagues in the early 1970s not only pioneered therapeutic endoscopy but set in motion a shift to its predominant use in the management of biliary stones ( Fig. 1 ). ES over the years has become well established as a safe technique, with an overall complication rate of approximately 5%. Additional early developments of tools such as extraction balloons and the Dormia basket led to successful endoscopic removal of bile duct stones in more than 80% of patients.

Demling and colleagues published the first experience of mechanical lithotripsy to fragment difficult stones and thereby facilitate successful removal in 1982. Mechanical lithotripsy has been shown to be a relatively simple and cost-effective way of fragmenting stones. This modality entails capturing the stone within a basket and then closing it against the metal sleeve of the basket catheter, causing fragmentation of the stone. A variety of both reusable and single-use through-the-scope mechanical lithotripsy devices are available. One of the major potential hazards of stone extraction using a standard plastic-sheathed basket is impaction of stone and basket at the level of the ampulla. In this situation a Soehendra-type “emergency” metal lithotripter sheath is passed over the impacted basket’s exposed wires, following cutting off the basket handle and removal of both the duodenoscope and the plastic sheath covering the basket wires. Under fluoroscopic guidance, additional traction is applied resulting in fragmentation of the stones or rupture of the basket wires, facilitating either stone or basket removal. Failure to have available or use this device has led to inadvertent surgical intervention. Demling’s study and other subsequent studies have shown mechanical lithotripsy to improve endoscopic bile duct clearance rates to approximately 90%.

Failure with the aforementioned modalities has been associated with the following clinical situations: (1) stones exceeding 2 cm in size; (2) limited sphincterotomy owing to anatomic constraints (small papilla, periampullary diverticulum); (3) stones proximal to a stricture or in difficult locations (cystic or intrahepatic ducts); and (4) impacted stones. The next 3 sections review the nonconventional methods used to remove difficult bile duct stones, and should be used only when the previously mentioned techniques have failed.

Balloon Sphincteroplasty

Endoscopic balloon dilation (EBD, sphincteroplasty) was introduced in 1983 by Staritz and colleagues as an alternative to ES for the treatment of bile stones. EBD refers to the controlled expansion of the sphincter of Oddi with a 4- to 8-mm dilation balloon, usually over 30 seconds to a few minutes. This action facilitates extraction of moderate-sized stones (5–8 mm) from the bile duct using conventional tools such as baskets or balloon catheters; however, this approach frequently requires mechanical lithotripsy for stones larger than 8 mm. Two meta-analyses comparing EBD and ES for stone clearance found similar success rates between the two therapies with a decreased rate of pancreatitis in the patients treated with ES. Although EBD offers theoretical advantages of a sphincter-preserving alternative to sphincterotomy, serious complications such as severe pancreatitis have brought the safety of this technique into question. One multicenter, randomized controlled trial of EBD versus ES was discontinued because of preliminary findings of increased risk of short-term morbidity and death related to pancreatitis in the EBD arm. Alternatively, EBD appears to carry a lower risk of bleeding and perforation, leading to its recommendation for treatment of choledocholithiasis in patients with coagulopathy.

In 2003, Ersoz and colleagues introduced a novel approach for the management of difficult stones that has since been termed endoscopic sphincterotomy with large balloon dilation (ESLBD) or endoscopic papillary large balloon dilation (EPLBD). A small sphincterotomy is made followed by a large (10–20 mm) balloon dilation, allowing for extraction of very large CBD stones ( Fig. 2 ). The size of the balloon is matched not to exceed that of the distal bile duct, and is inflated with contrast under fluoroscopic guidance until the waist at the level of the sphincter is obliterated. A recent meta-analysis comparing EPLBD with ES for treatment of large stones noted fewer complications in the EPLBD group and decreased need for mechanical lithotripsy. Unlike EBD, EPLBD does not appear to be associated with an increased risk of pancreatitis ( Table 1 ). The initial separation of biliary from pancreatic sphincters created by the biliary ES appears to then facilitate a controlled balloon-induced tear away from the pancreatic orifice. EPLBD seeks to combine the advantages of dilation with the safety profile of ES, and has thus far shown promising results in the United States and elsewhere.

Table 1

Results of EBD and EPLBD for the treatment of large CBD stones

Authors	No. of Trials/Patients	Balloon Size (mm)	Clearance (%)	Complications Overall/Pancreatitis (%)
EBD
Baron and Harewood	8/552	≤8	94	11/7
Weinberg et al	15/878	8–12	90	10/9
Disario et al	117	≤8	97	18/15
EPLBD
Feng et al	7/378	12–20	97	6/4
Ersoz et al	58	10–20	89	15/3
Draganov et al	44	10–15	84	7/0

Electrohydraulic Lithotripsy

When mechanical lithotripsy and or EPLBD have failed, shock-wave lithotripsy can be used to fragment bile duct stones and thereby facilitate removal. In electrohydraulic lithotripsy (EHL), shock waves are created in a liquid media by the generation of high-voltage sparks across a pair of electrodes at the tip of the EHL probe, which instantaneously evaporates fluid, creating a cavitation bubble. The oscillation of this bubble then forms a mechanical shock wave that subsequently fragments the stone, a process termed the electromechanic effect of EHL. EHL generates considerable thermal energy, which can cause significant bile duct injury and is thus performed under direct visual guidance.

Intraductal shock-wave lithotripsy can be performed under peroral cholangioscopic (POC) guidance currently by 1 of 2 methods. The mother-daughter endoscopic system has been in use since the 1970s and entails the passage of a cholangioscope (daughter) through the working channel of a duodenoscope (mother). This system requires 2 experienced endoscopists to operate the endoscopes. Ultrathin (3.1–3.4 mm) video cholangioscopes with 2-way tip deflection offer excellent imaging but tend to be fragile, requiring frequent repairs. Because of these limitations, this system has predominantly been restricted to use in high-volume academic centers.

The recently developed single-operator catheter-based system (SpyGlass; Boston Scientific, Natick, MA, USA) has gained increasingly widespread popularity since its introduction in 2005. This system uses a 10F (3.3 mm) disposable catheter with 4-way tip deflection and a reusable fiber optic probe. The catheter is passed over a guide wire through the working channel of the duodenoscope, and its 1.2-mm working channel allows for passage of an EHL probe or other tools such as biopsy forceps. Other channels in this catheter allow for passage of the optical probe and simultaneous fluid irrigation and/or aspiration. Whereas the mother-daughter system offers quality video imaging, the catheter-based system offers a slightly more user-friendly platform to perform intraductal lithotripsy.

EHL probes, typically 3F (1 mm) in diameter, are advanced through the working channel of the POC to the level of the stone. A foot pedal is used to activate 1- to 2-second impulses of EHL in 1- to 2-second bursts at energies ranging from 70 to 100 W. Continuous irrigation of saline into the bile duct seems to increase the conductance of the EHL. Repeat applications are performed until desired fragmentation is achieved.

Piraka and colleagues reported their prospective experience with cholangioscopy-guided EHL for the management of difficult bile duct stones in 30 patients. These patients had previously undergone a mean of 3.3 failed attempts at stone extraction using conventional endoscopic techniques. Complete stone clearance was achieved in 81% with a mean of 1.4 sessions of EHL, with 3 minor procedure-related complications. Long-term follow-up (mean 29 months) revealed recurrent stone formation in 18%.

Several other studies have reported favorable results with EHL, and are summarized in Table 2 . EHL appears to be effective in the fragmentation and removal of large bile duct stones in 79% to 98% of cases. Overall complication rates seen with this technique range from 3% to 15%. The potential for major complications (perforation, hemothorax, and bile leak) represent the major obstacle to using this technique. EHL creates a significant amount of thermal effect; considerable caution must be taken to keep the EHL probe in view and off the biliary mucosa to minimize the risk of ductal injury.

Table 2

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