Improved visualization of choledocholithiasis by sonography.

During a 20 month period, real-time sonography performed on 26 patients achieved an overall sensitivity of 75% for detecting choledocholithiasis. Although previous publications have stressed very low sensitivities for diagnosing choledocholithiasis (13%-55%), it was postulated that the reasons for these disappointing results are primarily related to technique. Most laboratories evaluate the distal common bile duct (where most calculi are located) by obtaining parasagittal scans. Detection of choledocholithiasis can be substantially improved by scanning the intrapancreatic part of the bile duct in a transverse fashion with the patient in an erect position. Advantages of the transverse view include the ability to demonstrate the distal common bile duct in a high percentage of patients and to differentiate shadowing caused by duodenal gas from ductal calculi. The proximal duct is best imaged by obtaining parasagittal scans with the patient in a supine left posterior oblique position. Using these scanning techniques, eight (89%) of nine proximal and 16 (70%) of 23 distal calculi were visualized.