Diagnostic Accuracy of Scintigraphy and Sonography for Biliary Atresia

Abstract

Objectives: To determine the diagnostic accuracy and predictive values of hepatobiliary scintigraphy and sonography in the evaluation of clinically suspected biliary atresia. Methods: All infants who underwent hepatobiliary scintigraphies for suspected biliary atresia within a 3-year period (2006–2008) in the New Territories East Cluster of Hong Kong were retrospectively analysed. All scintigraphies and peri-scintigraphic ultrasound images were reviewed for signs suggestive of biliary atresia. The accuracy of imaging studies was determined by surgical findings and clinical follow-up. Results: Forty-two cases were retrieved with two excluded due to incomplete clinical records. Seven (18%) of 40 patients had surgically confirmed biliary atresia; all of these had positive scintigraphies and 6/7 (86%) had positive sonographic findings. Among the 40 scintigraphies, there were 7 true-positive, 28 true-negative, and 5 false-positive studies. The scintigraphic sensitivity, specificity, and positive and negative predictive values were 100%, 85%, 58% and 100%, respectively. Among the 5 false-positive scintigraphies caused by hepatic dysfunction, 3 had normal sonography; 2 became negative on repeated scintigraphy, 2 had spontaneous clinical improvement, and 1 had normal intra-operative cholangiography. Thirty-eight of the 40 patients had performed peri-scintigraphic sonography. There were 23/38 (61%) abnormal studies which included cases with small gallbladder (n = 15) and non-visualised gallbladder (n = 8), but not periportal fibrosis. The sensitivity, specificity, positive and negative predictive values of these sonograms were 86%, 45%, 27% and 93%, respectively. Conclusions: Both hepatobiliary scintigraphy and sonography are currently the standard imaging investigations for suspected biliary atresia. This study revealed relatively low positive predictive value for biliary atresia by either investigation. We therefore consider their complementary role in which a correlation between scintigraphy and sonography is important, and recommend follow-up imaging reassessment before making definitive surgical decisions. This will serve to decrease the frequency of false-positive imaging diagnoses of biliary atresia, and hence, avoid unnecessary surgeries.