Prevalence of CBD Stones in Acute Pancreatitis
The prevalence of common bile duct (CBD) stones in patients with acute pancreatitis is approximately 50-56%, which is substantially higher than the 10-20% prevalence seen in patients with symptomatic gallstones without pancreatitis. 1, 2
Epidemiological Context
The high prevalence of CBD stones in acute biliary pancreatitis reflects the underlying pathophysiology—stones migrating through the CBD cause pancreatic duct obstruction at the ampulla of Vater, triggering the inflammatory cascade. 1 This mechanistic relationship explains why:
- Gallstones cause up to 50% of all acute pancreatitis cases, making CBD stone evaluation critical in this population 3, 1
- In prospective studies of patients undergoing early ERCP (<72 hours), 53-56% had persistent CBD stones at the time of intervention 2, 4
- This contrasts sharply with acute cholecystitis, where CBD stones occur in only 5-15% of cases 1
Temporal Considerations
The prevalence of persistent CBD stones remains stable during the first 7 days after symptom onset (approximately 20% prevalence), with no significant association between timing to surgery and presence of stones within this window (p=0.28). 2 However:
- After day 7, the prevalence of CBD stones increases significantly (p=0.007 and 0.005), likely reflecting spontaneous stone passage in some patients during the acute phase 2
- The overall prevalence of 19.91% (95% CI 14.96-25.65) in patients undergoing intraoperative cholangiography during the first week represents stones that persist despite conservative management 2
Clinical Implications for Risk Stratification
The substantially higher prevalence in acute pancreatitis (50-56%) compared to symptomatic gallstones (10-20%) mandates systematic evaluation for CBD stones in all patients with acute biliary pancreatitis. 1, 5 The American College of Gastroenterology recommends that decisions for ERCP should be guided by clinical factors and bilirubin levels given this high baseline risk. 1
Diagnostic Challenges
Commonly used biochemical and radiological predictors show poor accuracy in the earliest stages of acute biliary pancreatitis, with positive predictive values ranging only from 0.53 to 0.69 and negative predictive values from 0.46 to 0.67. 4 Specifically:
- GGT and alkaline phosphatase are the only parameters significantly associated with CBD stones (p=0.001 and p=0.028 respectively), but their clinical utility remains limited 4
- A simple scoring system using bilirubin ≥40 μmol/L, GGT ≥250 IU/L, alkaline phosphatase ≥225 IU/L, and age ≥70 years achieves 93% specificity but only 80% sensitivity 6
- Bilirubin alone has 80% sensitivity and specificity for CBD stones in acute pancreatitis 6
Common Pitfalls
- Do not assume stone passage has occurred even in patients with improving symptoms during the first week—the prevalence remains constant at approximately 20% throughout this period 2
- Normal liver function tests and ultrasound do not rule out CBD stones in acute pancreatitis, as predictive accuracy is poor in the acute phase 4
- The high prevalence necessitates a low threshold for advanced imaging (MRCP or EUS) or early ERCP in patients with severe pancreatitis, cholangitis, or persistent jaundice 7