MR cholangiography in symptomatic gallstones: diagnostic accuracy according to clinical risk group.

PURPOSE: To determine the diagnostic accuracy of magnetic resonance (MR) cholangiography in the detection of common bile duct (CBD) stones in patients with symptomatic gallstones.
MATERIALS AND METHODS: Single-shot half-Fourier MR cholangiographic images were obtained in 121 consecutive patients who were referred for MR cholangiography prior to cholecystectomy for symptomatic gallstones. One radiologist interpreted the MR cholangiographic images without prior knowledge of laboratory test results or findings from examinations with other imaging modalities. Patients were retrospectively divided into three groups with high, moderate, and low risk (n = 70, 22, and 29, respectively) for CBD stones. The sensitivity, specificity, and accuracy of MR cholangiography in the detection of CBD stones in each group were calculated. The accuracy of laboratory and sonographic findings in the identification of CBD stones was also calculated.
RESULTS: CBD stones were diagnosed in 49 (70%) of 70 patients in the high-risk group. One false-positive diagnosis was made, and two false-negative diagnoses were made. Of the 22 patients in the moderate-risk group, seven (32%) had CBD stones, and there was one false-positive and one false-negative diagnosis. In the low-risk group, CBD stones were correctly identified with MR cholangiography in one patient, and there was one false-positive diagnosis. A combination of positive laboratory and sonographic findings yielded a sensitivity of 98% but a specificity of only 34% if any unusual finding in any one of the tests was regarded as a positive finding.
CONCLUSION: MR cholangiography is highly accurate in the detection of CBD stones in all patients, regardless of the grade of risk, and should be considered in patients with a moderate to high risk of CBD stones before cholecystectomy. Copyright RSNA, 2002