Electrohydraulic lithotripsy (EHL) has emerged as a vital adjunct to endoscopic retrograde cholangiopancreatography (ERCP), providing an effective means of fragmenting large, impacted, or otherwise difficult-to-extract stones within the pancreatic and biliary ducts. This review integrates current evidence and technical considerations, with emphasis on clinical application by outlining the indications for EHL, strategies to optimize procedural safety, and its role in relation to mechanical lithotripsy, laser lithotripsy, and extracorporeal shock wave lithotripsy (ESWL).

Background

Electrohydraulic lithotripsy (EHL) is a critical adjunct to endoscopic retrograde cholangiopancreatography (ERCP) for the fragmentation of large, impacted, or otherwise difficult-to-remove pancreatic and biliary stones.^,,,, The technology generates microsecond-duration spark discharges at the probe tip that create cavitation bubbles, which collapse into high-pressure shock waves capable of fracturing mineralized concretions under direct vision.^, Over the past decade, integration of EHL with digital single-operator cholangioscopy has led to improved ductal clearance rates with acceptable adverse event rates in patients with difficult stones.^,

Indications for EHL Biliary Stones

For most common bile duct (CBD) stones, standard ERCP techniques such as sphincterotomy with balloon or basket extraction, and, in selected cases, endoscopic papillary large-balloon dilation
(EPLBD), achieve ductal clearance in a single session.^1,2 A subset of stones remains difficult to manage. EHL should be considered for stones ≥15–20 mm, those impacted proximal to a biliary stricture, intrahepatic calculi not amenable to standard techniques, and in patients where conventional extraction methods have proven unsuccessful.^,,,,,,,, (Figure 1) When performed under direct cholangioscopic visualization, EHL allows precise fragmentation of stone surfaces and is particularly valuable in cases where conventional or mechanical lithotripsy has limited efficacy.^3,6 Meta-analyses of cholangioscopy-guided lithotripsy consistently demonstrate technical success and ductal clearance rates of  ≥85–95%, with adverse event (AE) rates in the range of 8-10%, especially when performed under direct digital visualization.^3,4 The most frequently reported AEs include cholangitis, post-procedural fever, and, less commonly, pancreatitis; most are mild and manageable with supportive care.^3,4 The evidence suggests that EHL may be most effective when introduced earlier in the treatment course, rather than being deferred until after several unsuccessful ERCP attempts.¹² Pooled data from Jin et al. and Amaral et al. similarly demonstrated ductal clearance consistently exceeding 90% with acceptable adverse event rates ranging between 8-12%.^11,13 Recent systematic review by Manti et al. reported pooled ductal clearance rates of 90–94% with adverse event rates between 6–10%, confirming the efficacy of EHL in difficult biliary stones.

Pancreatic Duct Stones

In chronic calcific pancreatitis with obstructing main pancreatic duct stones, extracorporeal shock wave lithotripsy (ESWL) combined with ERCP continues to serve as the cornerstone of therapeutic management if stones cannot be removed via pancreatic sphincterotomy and balloon or basket extraction. Pancreatoscopy with intraductal lithotripsy (using either EHL or laser) has emerged as an effective second-line or alternative strategy, particularly in cases refractory to ESWL or when stones are concentrated in the head/neck adjacent to strictures.^,,, (Figure 2) These locations are particularly amenable to intraductal therapy, as direct visualization permits targeted fragmentation of impacted stones, while adjunctive maneuvers such as stricture dilation and temporary stenting facilitate fragment clearance and ductal drainage.^21,22,23,24

Systematic reviews have demonstrated high technical success rates and significant improvements in pain outcomes with this approach, with most adverse events related to mild post-ERCP pancreatitis.^23,24 Multicenter data from Gutierrez et al. demonstrated clearance rates > 95 % with low adverse event rates (< 5 %), confirming the safety and efficacy of digital cholangioscopy-guided lithotripsy in complex biliary stone disease.⁸ These findings support the use of pancreatoscopy with intraductal lithotripsy as a salvage therapy following failed ESWL and as a potential first-line option in patients whose anatomy or clinical profile favors direct intraductal intervention.^21,22,23,24

Set-up and Technique

Access and Visualization

For biliary stones, digital single-operator cholangioscopy performed in the context of ERCP offers a stable platform for targeted lithotripsy and subsequent stone retrieval. Adequate irrigation is essential to maintain a clear visual field, as rapid accumulation of debris can obscure visualization and potentially increase intraductal pressure.^5,6

For pancreatic stones, pancreatoscopy with intraductal lithotripsy requires careful advancement of the pancreatoscope to the level of the target stone to ensure stable positioning and safe energy delivery. This may include passage of the pancreatoscope across strictures, which may be technically challenging.²² In many cases, pre-dilation and temporary stent placement are required to facilitate passage of the scope through strictures to reach offending stones before EHL can even commence.^3,22 

Probe Selection and Energy Settings

Modern electrohydraulic lithotripsy (EHL) probes (1.9–2.5 Fr) are compatible with the working channel of digital single-operator cholangioscopy platforms, which can be applied for both biliary and pancreatic duct interventions. The commercially available electrohydraulic lithotripsy (EHL) probes used in gastrointestinal (GI) endoscopy are typically 1.9 French (F) and 3 French (F) in size, with vendors including Boston Scientific Autolith Touch Biliary EHL system and Walz Elektronik (Germany). These probes are designed for use through the working channel of cholangioscopes or pancreatoscopes during ERCP or direct peroral cholangioscopy and are compatible with both single-operator and mother-baby endoscopic systems.²⁷ Direct peroral cholangioscopy using multibending ultra slim endoscopes has further expanded therapeutic access to difficult bile duct stones. The 1.9F probe is most commonly used due to its compatibility with the narrow working channels of digital cholangioscopes (e.g., SpyGlass DS), while the 2.5F probe is used in larger-caliber scopes or for intraoperative applications.²⁷ Some suggest that power and frequency should be set at low-to-moderate levels, with stepwise escalation only as needed to gradually fragment the stone while limiting the risk of injury to the ductal wall, but in practice settings are left to the discretion of the operator.²⁷ Safe use requires frequent probe repositioning and delivery of short, focused bursts to the stone surface rather than the surrounding mucosa.^5,6

EHL probes have a limited life span, which is proportional to the potency chosen during the procedure. The American Society for Gastrointestinal Endoscopy, in its most recent guideline, does not specify an exact number of shocks or procedures per probe, but clinical studies referenced in the guideline and in the broader literature support the practical approach of monitoring probe function and replacing the probe when performance declines and/or failure occurs.

Irrigation Strategy

Continuous irrigation is necessary to dissipate heat, clear debris, and effectively transmit shock waves to target stones.²⁶ Liberal intermittent suction is recommended by some authors to reduce intraductal pressure, as high-pressure irrigation may increase the risk of cholangitis and post-procedural fever. Evidence regarding prophylactic antibiotics is inconclusive, with large studies showing limited overall benefit, although in general they are given to patients. Nevertheless, prophylaxis is indicated in specific contexts, including obstructed systems, primary sclerosing cholangitis, and procedures requiring prolonged intraductal manipulation.³²

Fragment Clearance

Following stone fragmentation, meticulous duct clearance is performed using balloons and retrieval baskets, while endoscopic papillary large balloon dilation (EPLBD) may be employed to expedite fragment removal when appropriate.^16,17 Cholangioscopy facilitates identification of residual stones or stone fragments that may have been overlooked on occlusion cholangiography; therefore, a final direct inspection is often performed prior to confirming complete ductal clearance.¹⁵

Outcomes and Comparative Effectiveness

Cholangioscopy-guided EHL vs conventional ERCP in Biliary Stone Management

Randomized trials demonstrate that cholangioscopy‑guided lithotripsy improves single‑session clearance and reduces the need for crossover to other rescue modalities (e.g., mechanical lithotripsy, repeat ERCP, or surgical intervention).¹⁸ This advantage derives from direct intraductal visualization, which allows targeted fragmentation of difficult stones while minimizing the need for multiple procedures.³ Several meta-analyses support these findings, showing high technical success rates and acceptable adverse event profiles when EHL is used earlier in the treatment course.^3,13 Korrapati et al. similarly reported ductal clearance rate of 88%, with an adverse event rate of 7%.⁴

Comparative Role of Mechanical, Laser, and Electrohydraulic Lithotripsy

Mechanical lithotripsy works by capturing the stone with a basket and fracturing it, which often allows immediate extraction.² In contrast, EHL and laser lithotripsy use energy-based fragmentation to break stones into smaller pieces that typically require balloon or basket extraction for clearance.² Mechanical lithotripsy remains the most established rescue modality for large or impacted bile duct stones, valued for its technical simplicity, low cost, and widespread availability. Mechanical lithotripsy achieves clearance in more than 85% of cases involving stones ≤15–20 mm. In contrast, success rates decline markedly when stones are very large, heavily calcified, or located intrahepatically, where basket capture may be difficult and/or incomplete.¹⁸

Laser lithotripsy has emerged as a highly effective alternative, particularly when combined with digital single-operator cholangioscopy.^10,12 It achieves high ductal clearance through precise photothermal fragmentation under direct visualization, with excellent fragmentation efficiency; pooled data suggest that in some series it may outperform EHL.^10,12 Its drawbacks include high equipment costs, requirement for specialized staff training, need for laser certification, and limited availability in many centers. 

EHL occupies an intermediate position when compared to laser lithotripsy: it is broadly accessible, compatible with existing single-operator cholangioscopy platforms, and consistently achieves ductal clearance with low adverse event rates.^8,10 Veld et al. found comparable safety between EHL and laser, with fragmentation efficiency numerically favoring laser, while overall clearance remained high for both technologies.¹⁰ Amaral et al. directly compared EHL with laser lithotripsy and confirmed both to be safe, with no significant difference in AE profile.¹¹

Pancreatoscopy with Intraductal Lithotripsy vs. ESWL

Pancreatoscopy with intraductal lithotripsy has demonstrated high technical and clinical success in patients with pancreatic duct stones, resulting in significant pain relief, with AE rates comparable to other ERCP-based therapies such as balloon or basket extraction, mechanical lithotripsy, and stenting.²² Comparative studies suggest that pancreatoscopy with intraductal lithotripsy may serve as a reasonable alternative to ESWL-first strategies, particularly when stone location, ductal strictures, or other anatomic factors favor direct intraductal therapy.^22,23 Careful multidisciplinary case selection and the use of staged stenting remain important to optimize safety and outcomes.^21,23 Staged stenting refers to the sequential placement of one or more temporary pancreatic duct stents, often upsized over multiple procedures, to facilitate ductal decompression, maintain drainage, and reduce the risk of procedure-related complications before or after intraductal lithotripsy. Systematic reviews by Huang et al. reported technical success rates of 90%.²⁴ Van der Weil et al. noted more than 50 % decrease in pain score or reduction in opioid usage at 6 months of follow-up.²² Meta-analysis by Guzmán-Calderón et al. also demonstrated a pooled technical success rate of 91% and overall adverse event rates of  approximately 12%, the majority of which were mild and self-limited.

Adverse Events Related to Cholangioscopy-Guided Lithotripsy

Meta-analyses of cholangioscopy-guided lithotripsy report overall AE rates of approximately 7%, most often transient fever or cholangitis, with the majority classified as mild.¹⁹ For pancreatoscopy with intraductal lithotripsy, pooled analyses show overall AE rates of 12%, again largely mild and self-limited, with post-ERCP pancreatitis (PEP) the most common event.^22,23 Severe adverse events are uncommon but have been described, including cholangitis with sepsis (2-4%) and perforation (1%).^4,

Troubleshooting and Special Scenarios

Impacted Proximal/Hilar Stones and Intrahepatic Bile Duct Stones

Impacted proximal/hilar and intrahepatic stones are particularly challenging because conventional balloon or basket extraction is often unsuccessful, owing to their location and the limited maneuverability of the balloon and extraction basket.⁹  In such cases, the strategy involves using a lithotripsy probe to debulk the central portion of the stone first, creating space for subsequent peripheral fragmentation.⁹ Prior and recent studies confirm the feasibility of EHL for intrahepatic stones, although multiple staged sessions may be required to achieve complete clearance.⁹

Cystic-duct Stones and Mirizzi Syndrome

Cystic-duct stones and Mirizzi syndrome are technically demanding scenarios where conventional ERCP often fails because of the angulated cystic-duct takeoff and stone impaction. Mirizzi syndrome is defined as extrinsic compression of the common hepatic duct by an impacted stone in the cystic duct or gallbladder. Patients with Mirizzi syndrome may also have cholecysto-choledocho fistulas, complicating matters significantly. Cholangioscopy-guided EHL provides a valuable alternative to surgical intervention, enabling targeted fragmentation and clearance of stones in patients who might otherwise require cholecystectomy or complex biliary reconstruction.⁴⁰ Pawa et al. reported 21 patients with cystic-duct stones managed with cholangioscopy-guided EHL, achieving 87% clearance with adverse events in 7%, limited to mild post-ERCP pancreatitis and transient fever.⁴⁰ Despite these successes, repeat sessions are frequently required.⁴⁰ Adjunctive balloon or basket extraction is necessary for fragment clearance after lithotripsy.^16,17 Temporary stenting has also been described as an important adjunct to maintain drainage and reduce the risk of recurrent obstruction between procedures.^21,22,23,24

Altered Anatomy or Enteroscopy-Assisted ERCP

EHL can be performed during device-assisted ERCP in patients with surgically altered anatomy, including those with Roux-en-Y gastric bypass, Billroth II gastrectomy, or hepaticojejunostomy. In these settings, an enteroscope is often required to access the biliary-enteric anastomosis or the papilla, but the long length and narrow working channel of the enteroscope impose technical limitations that can restrict accessory use and fragment retrieval.⁴²

Pancreatic Duct Strictures

Pre-dilation of high-grade strictures and staged pancreatic duct stenting can facilitate pancreatoscope passage and fragment clearance in patients with pancreatic duct stones upstream of pancreatic duct strictures.²³ This strategy often involves sequential stent exchanges with gradual upsizing to “remodel” the stricture, decompress the duct, and permit easier reintroduction of the pancreatoscope during subsequent sessions.³⁶ Temporary stenting also helps reduce the risk of procedure-related pancreatitis by maintaining drainage between interventions.³⁶ In the head and neck of the pancreas, where the duct is more tortuous and mucosal surfaces are thin, short and controlled EHL bursts with continuous irrigation are strongly recommended to optimize visualization and minimize the risk of thermal or mechanical injury.³¹ Careful irrigation control is particularly important in these regions, as excessive fluid infusion can elevate intraductal pressure and increase the risk of post-ERCP pancreatitis.³¹

Conclusions

Electrohydraulic lithotripsy (EHL) is an effective option for the management of difficult biliary and pancreatic duct stones. Evidence supports its role both as a rescue therapy and as an early option when conventional ERCP is unlikely to achieve clearance. Cholangioscopy-guided EHL achieves high success rates with mostly mild, manageable adverse events. Pancreatoscopy with intraductal lithotripsy is a useful option for pancreatic stones, offering an alternative to ESWL in patients refractory to standard treatment strategies. EHL occupies a middle ground among intraductal therapies. It is more effective than mechanical lithotripsy in complex scenarios, less costly, more widely available than laser, and broadly compatible with existing endoscopic platforms. Its safety and efficacy depend on careful techniques, including direct visualization, controlled irrigation, conservative energy use, and staged procedure when needed. EHL offers a reliable and accessible option for complex stone disease, with ongoing studies continuing to clarify its role within advanced endoscopic practice.  

References

Download Tables, Images & References