title: Selective use of magnetic resonance cholangiopancreatography in clinical practice may miss choledocholithiasis in gallstone pancreatitis.
abstract: BACKGROUND
  Gallstone pancreatitis is a consequence of ampullary obstruction by common bile duct (CBD) calculi. Magnetic resonance cholangiopancreatography (MRCP) has been advocated for routine use to diagnose choledocholithiasis. However, the selective use of MRCP in clinically equivocal situations has not been explored until now. This study examines the diagnostic value of selective MRCP in gallstone pancreatitis.
  
  
  METHODS
  We conducted a retrospective audit of all presentations of gallstone pancreatitis between January 2001 and December 2007 at Middlemore Hospital, Auckland, New Zealand. Demographic data, clinical presentation, biochemical and radiological findings and outcomes were reviewed.
  
  
  RESULTS
  There were 339 cases of gallstone pancreatitis during the study period; 236 patients were women and the mean age was 52 years. Overall, choledocholithiasis was diagnosed in 95 patients. A total of 117 patients underwent MRCP within a median of 4 days of admission, with 15 (13.7%) showing choledocholithiasis. There was no significant difference in time to MRCP between positive and negative groups. Endoscopic retrograde cholangiopancreatography (ERCP)/intraoperative cholangiography (IOC) confirmed 13 of 15 stones within a median of 2.5 days. However, MRCP missed 8 cases of choledocholithiasis subsequently demonstrated on ERCP/IOC, where clinical suspicion remained after a negative MRCP. Its sensitivity was 62% and specificity 98%. The positive likelihood ratio was 6.5 and the negative likelihood ratio was 0.1. In all, 222 patients followed different clinical pathways with 82 CBD stones diagnosed by ERCP/IOC.
  
  
  CONCLUSIONS
  Selective MRCP is highly specific in gallstone pancreatitis but may not be sensitive enough to exclude choledocholithiasis in this context.
authors.affiliation: The South Auckland Clinical School, Department of Surgery, University of Auckland, Auckland, New Zealand.
authors.forename: Sanket
authors.initials: S
authors.lastname: Srinivasa
authors.forename: Tarik
authors.initials: T
authors.lastname: Sammour
authors.forename: Bernard
authors.initials: B
authors.lastname: McEntee
authors.forename: Nicola
authors.initials: N
authors.lastname: Davis
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Hill
mesh_terms: D002758:Cholangiography; D002760:Cholangiopancreatography, Endoscopic Retrograde; D049448:Cholangiopancreatography, Magnetic Resonance; D042883:Choledocholithiasis / Q000175:diagnosis*; D005260:Female; D042882:Gallstones / Q000175:diagnosis* / Q000601:surgery; D006801:Humans; D007432:Intraoperative Period; D016013:Likelihood Functions; D008297:Male; D008485:Medical Audit; D008875:Middle Aged; D009520:New Zealand; D010195:Pancreatitis / Q000209:etiology*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity