Diagnosis of choledocholithiasis: value of MR cholangiography

T2-weighted fast spin-echo MR imaging (MR cholangiography) of the right upper quadrant of the abdomen depicts the biliary tree in considerable detail. We studied the value of this procedure for detecting stones in the common bile duct in a series of patients with proved calculi.

MR images of 10 consecutive patients with stones in the common bile duct were retrospectively reviewed. The diagnosis of choledocholithiasis was proved by stone extraction in all cases. Axial, coronal, and oblique images were obtained by using heavily T2-weighted fast spin-echo sequences, and the images were processed by using a maximum-intensity-projection (MIP) algorithm and a commercially available multiplanar reformatting software. Two reviewers who were not blinded to the diagnosis analyzed hard copy images and reformatted images at the MR console. The rate of stone detection was evaluated for each acquisition plane. The mean stone/bile signal-intensity ratio and the number and size of stones were recorded.

In all patients, the entire length of the extrahepatic bile ducts was visualized, and the diagnosis of choledocholithiasis could be made on the basis of findings on MR images. Eight stones, including two that were impacted in the ampulla, were located in the distal part of the common bile duct. On the hard copy films, the stones were visible in eight of 10 coronal images, six of 10 axial images, and four of 10 oblique images. On the three-dimensional (3D) MIP reconstructions, the stones were seen in five of the coronal sets and in six of the axial sets. The best results were obtained when the multiplanar reconstruction software was used: nine of the 10 coronal sets and eight of the 10 axial sets showed stones in the bile ducts. By use of a combination of 3D MIP and multiplanar reconstruction, choledocholithiasis was detected in all 10 patients. The mean signal intensity of the stones was 58 (range, 18-87). The mean stone/bile signal-intensity ratio was 0.15 (range, 0.05-0.24).

In this preliminary study, we showed that MR cholangiography, based on T2-weighted fast spin-echo sequences, could be an important imaging technique for patients with suspected bile duct obstruction and equivocal sonography and/or CT results. However, a large prospective clinical trial is needed to confirm these results.