A 58-year-old man with a 10-year history of cholelithiasis is admitted with sudden onset severe epigastric pain radiating to the back, persistent vomiting, and elevated serum lipase (820 U/L). Abdominal ultrasound shows gallstones, a dilated common bile duct (8 mm), and no evidence of acute cholecystitis. CT abdomen reveals pancreatic oedema. What is the most likely diagnosis, and what is the next step in management?

Explanation

## Clinical Diagnosis **Key Point:** This is **acute pancreatitis secondary to choledocholithiasis** (gallstone-induced biliary pancreatitis). ### Diagnostic Clues | Finding | Interpretation | |---------|----------------| | Sudden severe epigastric pain + vomiting | Acute pancreatitis | | Elevated lipase (820 U/L) | Pancreatic inflammation (>3× ULN confirms pancreatitis) | | Gallstones on ultrasound | Biliary source | | Dilated CBD (8 mm, normal <6 mm) | Obstruction by stone | | Pancreatic oedema on CT | Acute interstitial pancreatitis | | **No acute cholecystitis** | Rules out primary gallbladder inflammation | ## Pathophysiology of Biliary Pancreatitis 1. **Stone migration** into the common bile duct 2. **Transient obstruction** of the ampulla of Vater 3. **Increased intraductal pressure** → reflux of bile into pancreatic ducts 4. **Activation of pancreatic enzymes** → inflammation and autodigestion 5. Resolution typically occurs within 24–48 hours as stone passes or retracts ## Management Algorithm ```mermaid flowchart TD A["Acute pancreatitis + Gallstones"]:::outcome --> B{"Choledocholithiasis confirmed?"}:::decision B -->|"Yes (dilated CBD, stone on imaging)"| C["Severity assessment"]:::action C --> D{"Severe pancreatitis?"}:::decision D -->|"Yes (APACHE ≥8, organ failure)"| E["ERCP within 24-48 hrs"]:::action D -->|"No (mild-moderate)"| F["ERCP within 24-72 hrs"]:::action E --> G["Sphincterotomy + stone extraction"]:::action F --> G G --> H["Supportive care (fluids, analgesia)"]:::action H --> I["Cholecystectomy after pancreatitis resolves"]:::action B -->|"No (normal CBD)"| J["Supportive care only"]:::action ``` **High-Yield:** In **biliary pancreatitis with confirmed choledocholithiasis**, ERCP with sphincterotomy and stone extraction is indicated within 24–72 hours (earlier in severe pancreatitis or cholangitis). **Clinical Pearl:** - ERCP is **therapeutic** in biliary pancreatitis (removes obstructing stone, relieves pressure) - It is **not diagnostic** in this case (diagnosis is already clear from imaging + lipase) - Cholecystectomy is performed **after** pancreatitis resolves (usually 2–4 weeks later) to prevent recurrence ## Why Not Cholecystectomy Now? Emergency cholecystectomy in acute pancreatitis is **contraindicated** because: - Inflamed pancreas is friable and at risk of iatrogenic injury - Increased operative morbidity and mortality - ERCP alone addresses the obstructing stone and relieves the primary problem [cite:Harrison 21e Ch 310; Robbins 10e Ch 18]