2 The condition, current treatments and procedure
2.1 Bile duct stones, which form from cholesterol or bile pigments, can block the bile ducts. Difficult-to-treat bile duct stones are defined by their diameter (above 15 mm), number, unusual shape (such as barrel-shaped), location (intrahepatic or cystic duct), stone impaction, narrowing of the bile duct distal to the stone, or the anatomy of the common bile duct (sigmoid-shaped, short distal length or acute distal angulation of less than 135 degrees).
2.2 Diagnosis and management of bile duct stones is described in the section on managing common bile duct stones in NICE's guideline on gallstone disease. Treatments for bile duct stones include bile duct clearance and laparoscopic cholecystectomy. Conventional stone extraction involves endoscopic retrograde cholangiopancreatography and a sphincterotomy, then extracting the stones from the ducts using balloon and basket catheters. For difficult-to-treat bile duct stones, treatment options include temporary stenting to allow biliary drainage if the stones cannot be removed or stone fragmentation (lithotripsy).
2.3 Laser lithotripsy aims to fragment bile duct stones that cannot be treated using conventional endoscopic stone removal techniques.
2.4 This procedure is usually done using general anaesthesia and direct visualisation of the stones using an endoscope inserted into the biliary tract. A laser fibre is introduced gently through the endoscope. Once the tip of the fibre is in direct contact with the stone, a laser is focused on its surface to create a plasma bubble. This oscillates and induces cavitation with compressive waves to fragment the stone. The procedure is usually done with the endoscope passed orally and through the stomach into the duodenum. However, a percutaneous approach is also possible.
2.5 When the stone fragmentation is complete, the fragments are removed by conventional methods (such as a basket or balloon catheter). The endoscope is then removed. Any small sand-like pieces may be retained and will be gradually passed through the body. The procedure usually takes 30 to 60 minutes.