Introduction: The aim of this study was to identify whether magnetic resonance cholangiopancreatography (MRCP) can be used selectively in patients with acute gallstone pancreatitis to detect choledocholithiasis, based on liver function tests (LFTs) and ultrasonography appearance.
Methods: All patients admitted between January 2008 and January 2011 with gallstone pancreatitis (amylase >300u/l) who underwent MRCP were included in the study. LFTs and radiology reports were obtained from the respective computer systems.
Results: Overall, 173 patients with acute gallstone pancreatitis underwent MRCP and 30% (52/173) showed choledocholithiasis. The mean bilirubin level was significantly higher in those with choledocholithiasis (46 ±5μmol/l vs 36 ±3μmol/l, p=0.0388) although there was no significant difference in alkaline phosphatase (276 ±25iu/l vs 229 ±16iu/l, p=0.1154). However, sensitivity of abnormal bilirubin (>21μmol/l) for choledocholithiasis was only 62% and specificity was 41%. Sensitivity of abnormal alkaline phosphatase (>140iu/l) for choledocholithiasis was only 75% and specificity was 37%. There was a significant association between biliary dilatation on ultrasonography and choledocholithiasis on MRCP (p=0.0099) although the sensitivity of biliary dilatation for choledocholithiasis was only 44% and the specificity was 79%. Furthermore, there was no difference in the incidence of choledocholithiasis on MRCP for those patients with persistently deranged LFTs versus those whose LFTs returned to normal (relative risk: 1.07, 95% confidence interval: 0.61-1.89, p=1.00). Overall, 10% of patients with choledocholithiasis on MRCP had entirely normal LFTs on admission and no biliary dilatation or choledocholithiasis on ultrasonography.
Conclusions: All patients with acute gallstone pancreatitis should undergo specific imaging, preferably MRCP, to exclude choledocholithiasis as LFTs and ultrasonography are inaccurate in predicting common bile duct stones.