Ultrasonography of choledocholithiasis.

In a retrospective study of patients with ultrasonographically demonstrable choledocholithiasis, 81 stones were demonstrated in 46 patients. The majority of the stones were between 5 and 10 mm in diameter; the smallest was 2 mm and the largest 23 mm. Of the 81 stones, 64 demonstrated acoustical shadowing; 56 were located in the distal segment of the common bile duct. Stones in the common bile duct are best demonstrated by sagittal sections with the patient in the right anterior oblique position. It is possible but more difficult to demonstrate stones within a normal-sized common bile duct. Several possible sources of confusion in the diagnosis of common bile duct stones are discussed. Ultrasonography of the common bile duct is best performed with a high-resolution real-time sector scanner. The accuracy and frequency of detection of common bile duct stones have increased significantly with the advances in technology and improvement in resolution of the mechanical sector real-time scanners.