The recent guidelines1 on the role of endoscopy in the evaluation of suspected choledocholithiasis are a valuable resource for clinicians and contain a comprehensive review of the role of US in predicting the probability of choledocholithiasis. Historically, a single maximum value has been used to answer the question, "Is the duct obstructed?" and has been chosen to give a compromise between best sensitivity and best specificity. The guidelines propose a bile duct diameter of greater than 6 mm as a strong predictor of choledocholithiasis in patients with their gallbladder in situ. This value, however, is much greater than the mean duct diameter denned in studies of normal patients, particularly in younger age groups.
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