# Choledocholithiasis > Choledocholithiasis in FMGE Surgery: CBD stone risk criteria, MRCP versus ERCP, sphincterotomy, stone extraction and cholecystectomy timing. - Canonical URL: https://prepelephant.com/topics/fmge/surgery/choledocholithiasis-fmge - Exam / course: FMGE · Subject: Surgery - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Choledocholithiasis", PrepElephant, https://prepelephant.com/topics/fmge/surgery/choledocholithiasis-fmge ## Direct answer Gallstones migrate from the gallbladder into the common bile duct in roughly one in seven patients with symptomatic cholelithiasis, and the duct stone then declares itself through jaundice, pancreatitis or cholangitis rather than through pain alone. Diagnosis has shifted decisively to risk-stratified imaging: patients with cholangitis, bilirubin above 4 mg/dL, or a dilated duct with stones on ultrasound proceed straight to ERCP, while intermediate-risk patients get MRCP or endoscopic ultrasound first so that ERCP is used therapeutically, not diagnostically. Definitive treatment is endoscopic sphincterotomy with stone extraction followed by cholecystectomy in the same admission, with laparoscopic common bile duct exploration as a single-stage alternative in equipped centres. ## What you must remember - **Composition clue:** duct stones are usually cholesterol stones migrated from the gallbladder; de novo brown pigment stones form within the duct behind strictures or stasis. - **High-risk criteria (ASGE):** CBD stone with cholangitis, serum bilirubin above 4 mg/dL, or a dilated duct (more than 6 mm) plus gallbladder stones — go directly to ERCP. - **Intermediate-risk markers:** abnormal liver tests, age above 55, or a duct measuring 6-8 mm — confirm with MRCP or endoscopic ultrasound before intervening. - **Therapeutic ERCP:** sphincterotomy, balloon or basket extraction, mechanical lithotripsy for large stones, and nasobiliary drain or plastic stent when clearance fails. - **Cholecystectomy timing:** same admission or within 2-4 weeks; delaying beyond that carries a real risk of recurrent duct stones, cholangitis or gallstone pancreatitis. - **Single-stage option:** laparoscopic CBD exploration via transcystic or choledochotomy route clears the duct and removes the gallbladder under one anaesthesia where expertise exists. - **Complications to anticipate:** post-ERCP pancreatitis, haemorrhage, perforation and retroperitoneal air; retained stones present with recurrent jaundice or cholangitis weeks later. ## Worked example: the intermediate-risk patient A 46-year-old man has biliary colic, total bilirubin 2.6 mg/dL, mildly raised alkaline phosphatase and an ultrasound showing a 7 mm CBD with gallbladder stones but no definite duct stone. He is intermediate risk, so the correct next step is not ERCP — exposing him to pancreatitis for a stone that may not exist — but MRCP. If MRCP shows an 8 mm distal stone, he undergoes ERCP with sphincterotomy and balloon extraction, and laparoscopic cholecystectomy before discharge. If MRCP is negative, he goes straight to cholecystectomy, treating the source and sparing the sphincter. Notice how each branch answers a different exam question: "best next investigation" (MRCP), "definitive treatment" (ERCP plus cholecystectomy), and "why not ERCP now" (risk stratification). In a smaller Indian centre without MRCP, intraoperative cholangiography or on-table duct exploration covers the same decision honestly. ## Where students slip The classic error is treating ERCP as the first investigation for every jaundiced patient with stones; modern papers reward risk stratification, so quote bilirubin thresholds and duct diameters rather than reflexes. A second slip is forgetting that the job is unfinished after ERCP — a patient whose gallbladder is left behind is a readmission waiting to happen, and "what further treatment" in the stem is almost always cholecystectomy. Finally, do not confuse jaundice from a duct stone with jaundice from cholangitis: the former needs scheduled clearance, the latter needs antibiotics and urgent drainage. ## Frequently asked questions ### Which patients with suspected duct stones go straight to ERCP? Those with cholangitis, bilirubin above 4 mg/dL, or ultrasound evidence of a dilated duct with stones — the high-probability group in whom therapeutic ERCP is justified without further testing. ### What is the best investigation in intermediate-risk patients? MRCP, or endoscopic ultrasound where available, because both detect duct stones accurately without ERCP's risk of pancreatitis. ### What size defines a dilated common bile duct? Roughly above 6 mm in an adult, with allowance for a slightly wider duct after cholecystectomy and in the elderly. ### How are large duct stones cleared at ERCP? Mechanical lithotripsy fragments the stone before basket extraction, and a plastic stent or nasobiliary drain buys time when clearance fails in one sitting. ### Can the duct and gallbladder be cleared in one operation? Yes — laparoscopic CBD exploration via the transcystic route or a choledochotomy achieves single-stage clearance in centres with the requisite skills.