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Background: Patients with symptomatic cholelithiasis and suspected choledocholithiasis can be risk stratified into a low (<10%), intermediate (10-50%) or high probability (>50%) of having CBD stone disease based on clinical predictors. Guidelines recommend laparoscopic cholecystectomy for patients with low probability of common bile duct (CBD) stone, pre-operative Endoscopic retrograde cholangiopancreatography (ERCP) for high probability of CBD stone and pre-operative Endoscopic ultrasound (EUS) or Magnetic resonance cholangiopancreatography (MRCP) or Intra-operative cholangiography (IOC) for intermediate probability of cholidocholithiasis. In patients with intermediate probability, ERCP is often deferred due to its potential complications and MRCP is commonly performed as EUS is not widely available. However, the diagnostic utility of MRCP in this sub set of patients is not well defined in clinical practice.
Methods: Charts of all patients admitted with symptomatic cholelithiasis that had cholecystectomy and underwent prior MRCP for cholidocholithiasis between the periods of Jan 2007 and Oct 2012 at an academic tertiary referral center were reviewed. Of these, patients who met the criteria for intermediate likelihood of CBD stone and underwent preoperative MRCP, IOC or pre/post- operative ERCP were included in the study. Patients with any intrinsic liver disease, or hepato-biliary malignancy or < 18 years of age were excluded. Pertinent demographic, clinical, biochemical and ultrasound parameters were collected by three investigators.
Results: Of a total of 330 patients, 125 met the inclusion criteria for intermediate probability and were included in final analysis. Mean age of all patients was 52±21 years with 37 % males (n=46). Eighty four patients had IOC and sixty patients had ERCP. MRCP was positive for CBD stone in only 26.4% of patients (n=33/125). CBD stone was present in 33% (n=41/125) patients as confirmed by either IOC (n=11/84) or ERCP (n=32/60). False positive rate of MRCP was 36% (12/33) and false negative rate was 21% (n=20/92). Sensitivity and specificity of MRCP in detection of impacted stone was 51% and 85% respectively. Positive predictive and negative predictive values were 63% and 78 % respectively.
Conclusion: MRCP has a poor sensitivity in patients with intermediate likelihood of cholidocholithiasis. Intraoperative cholangiography is recommended for definitive evaluation for a residual bile duct stone in this sub group.