Diagnosing bile duct stones: comparison of unenhanced helical CT, oral contrast-enhanced CT cholangiography, and MR cholangiography.

OBJECTIVE In this investigation we compared the diagnostic performance of unenhanced helical CT, oral contrast-enhanced CT cholangiography, and MR cholangiography for the diagnosis of choledocholithiasis. SUBJECTS AND METHODS Fifty-one patients referred for endoscopic retrograde cholangiography of suspected biliary stones were studied with unenhanced helical CT, MR cholangiography, and helical CT performed after oral administration of a cholangiographic contrast agent (iopodic acid). The studies were randomized for interpretation. Two radiologists evaluated the images by consensus and determined the presence and location of stones. We used retrograde cholangiography findings as the standard of reference. Sensitivity and specificity (with 95% confidence intervals [CIs]) of the three examinations were calculated and compared using the exact form of the McNemar test. RESULTS Bile duct stones were revealed with retrograde cholangiography in 26 patients (51%). Sensitivity was 65% (95% CI, 44.4-82%) for unenhanced helical CT, 92% (95% CI, 73-99%) for CT cholangiography, and 96% (95% CI, 78-99%) for MR cholangiography. Specificity was 84% (95% CI, 63-95%) for unenhanced helical CT, 92% (95% CI, 73-99%) for CT cholangiography, and 100% (95% CI, 83-100%) for MR cholangiography. The sensitivity of CT cholangiography and MR cholangiography was significantly higher than that of unenhanced helical CT (p<0.01). Differences in specificity were not significant. CONCLUSION Our results indicate that oral contrast-enhanced CT cholangiography and MR cholangiography are significantly more sensitive than unenhanced helical CT for the detection of bile duct calculi.