When should electrohydraulic lithotripsy be used for common bile duct stones and how is the procedure performed?

Electrohydraulic Lithotripsy for Common Bile Duct Stones

Electrohydraulic lithotripsy (EHL) should be used when standard endoscopic stone extraction techniques—including mechanical lithotripsy, balloon dilation with prior sphincterotomy, and basket extraction—have failed to clear the bile duct. 1

When to Use EHL

Indications

EHL is reserved for difficult bile duct stones that cannot be removed by conventional methods. The 2017 BSG guidelines provide a clear algorithmic approach:

First-line treatment:

• Biliary sphincterotomy with balloon or basket extraction 1
• For large stones: add endoscopic papillary balloon dilation (EPBD) after sphincterotomy 1

Second-line treatment:

• Mechanical lithotripsy
• EPBD with prior sphincterotomy 1

Third-line treatment (when above fail):

• Cholangioscopy-guided EHL or laser lithotripsy 1

The ESGE 2019 guidelines similarly recommend cholangioscopy-assisted intraluminal lithotripsy (electrohydraulic or laser) as effective and safe for difficult bile duct stones 2.

Stone Characteristics Requiring EHL

• Large stones (typically >15 mm) that cannot be extracted intact 3
• Stones in narrow caliber bile ducts 3
• Impacted stones 4
• Stones that have failed 1-2 prior ERCP attempts with standard techniques 3

How the Procedure is Performed

Technical Principles

EHL works by generating a shock wave from rapid thermal expansion of fluid caused by a high-voltage spark. This hydraulic pressure wave fragments the stone 1. The key safety requirement is that energy delivery must be conducted under direct vision to ensure precise targeting and prevent bile duct injury 1.

Procedural Steps

1. Cholangioscopy Access:

• Single-operator cholangioscopy (SOC) systems like SpyGlass are now standard 1
• The cholangioscope passes through the duodenoscope
• Newer digital platforms (SpyGlass DS, introduced 2015) provide improved visualization 1

2. Stone Fragmentation:

• EHL probe is advanced through the cholangioscope
• Under direct visualization, the probe tip is positioned against the stone
• High-voltage sparks are delivered to fragment the stone 1
• Continue until fragments are small enough for basket/balloon extraction

3. Fragment Removal:

• All patients with successful fragmentation require post-EHL balloon or basket extraction of fragments 3
• May need additional mechanical lithotripsy for larger fragments 5

4. Sessions Required:

• 76% of patients need only 1 EHL session
• 14% require 2 sessions
• 10% require 3 or more sessions 3

Alternative Technique (Without Cholangioscopy)

For select cases, fluoroscopically-controlled EHL using a balloon catheter can be performed without direct visualization 5. However, this is less preferred as direct vision is safer and more effective.

Expected Outcomes

Efficacy

• Stone fragmentation rate: 96% 3
• Final duct clearance rate: 73-97% with cholangioscopy-guided approach 1
• Complete clearance: 90% when including post-fragmentation extraction 3

These high success rates make EHL an important advance in managing difficult bile duct stones 1.

Safety Considerations

Prophylactic Measures

Antibiotics are mandatory because cholangitis occurs in up to 9% of patients undergoing cholangioscopy 1.

Complications

The procedure is generally safe with complications comparable to conventional ERCP 1:

• Cholangitis/jaundice: 13.8% 3
• Mild hemobilia: 1% 3
• Post-ERCP pancreatitis: 1% 3
• Biliary leak: 1% 3
• No procedure-related deaths reported 3

Common Pitfalls

• Blind instrumentation is dangerous: Always use direct visualization to avoid bile duct perforation and trauma that increases stricture risk 1
• Incomplete fragment removal: Don't assume small fragments will pass spontaneously—actively extract all visible fragments 3
• Inadequate sphincterotomy: Ensure adequate papillary opening before attempting fragment extraction

Alternative Approaches When EHL Unavailable or Fails

If EHL is not available or fails (4% fragmentation failure rate 3):

1. Laser lithotripsy (equally effective alternative) 1, 2
2. Percutaneous transhepatic approach with EHL or other lithotripsy 6, 7
3. Surgical bile duct exploration (last resort, carries 20-40% morbidity and 1.3-4% mortality) 6

The percutaneous approach achieves 95-100% success but has a 3.6-6.8% major complication rate 1.