Objective: To evaluate the diagnostic performance of endoscopic ultrasound (EUS) in patients with unexplained dilated CBD on MRCP. Subject and method: 28 patients referred for EUS evaluation of a dilated CBD were retrospectively analyzed with respect to serum alkaline phosphate prior to EUS and subsequent outcome after EUS over a 1-year period. Result: 28 patients (11 males
mean age 54.4 years) with dilated CBD were retrospectively identified. Ten patients had elevated serum alkaline phosphate. The diagnosis obtained after EUS examination was: CBD stones in 10 patients (37.5 percent) with largest size of CBD stone being 10 mm, mass in CBD in 1 patient (3.5 percent), benign biliary stricture in 2 patients (7.1 percent), biliary stricture with underlying chronic pancreatitis in 1 patient (3.5 percent) patient, respectively. EUS examination revealed normal CB in 13 (46.4 percent) patients and two of these patients had periampullary diverticulum. All patients with abnormal liver function tests had a detectable CBD disease whereas 14/21 (66.6 percent) patients with normal liver biochemistry had normal EUS findings. There was no significant difference in the mean CBD diameter between the groups with and without disease finding (p0.05). Conclusion: EUS is a useful investigation modality for patients with unexplained dilated CBD on MRCP. Underlying disease can not be ruled out in patients with normal mean CBD diameter and liver function tests.