Diagnostic Accuracy of Scintigraphy and Sonography for Biliary Atresia
HKY Tam, PPY Lui, RKL Lee, WK Kwok, FPT Choi, WCW Chu
Hong Kong J Radiol 2013;16:278-85
DOI: 10.12809/hkjr1313203
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.
中文摘要
膽道閉鎖核素顯像和超聲診斷的準確性
譚家盈、呂沛欣、李嘉樂、郭永剛、蔡柏達、朱昭穎
目的：探討肝膽核素顯像和超聲對臨床疑診為膽道閉鎖病例的診斷準確性和預測值。
方法：回顧分析香港新界東聯網於2006至2008年的三年期間，懷疑患有膽道閉鎖而須接受肝膽核素顯像的所有嬰兒。審視病人的核素顯像和核素顯像期間的超聲檢查以找出膽道閉鎖的跡象，然後以手術結果和臨床隨訪來確定影像學的準確性。
結果：42例中有兩例因臨床記錄不完整而不被列入研究範圍。餘下的40例中，7例（18%）以手術證實膽道閉鎖，這些患者核素顯像均呈陽性結果，6例（86%）的超聲呈陽性結果。40例核素顯像中，7例呈真陽性、28例呈真陰性、5例呈假陽性的顯像結果。核素顯像的敏感性、特異性、陽性和陰性預測值分別為100%、85%、58%和100%。5個因肝功能障礙而引致的假陽性顯像結果中，3例出現正常的超聲結果；2例在重複進行顯像時出現陰性結果，2例自發性有臨床症狀改善，1例術中膽管造影正常。40例中有38例進行了核素顯像期間的超聲檢查，其中23例（61%）出現異常結果，包括小膽囊（n = 15）和膽囊未見（n = 8），但無肝門區纖維化的病例。超聲的敏感性、特異性、陽性和陰性預測值分別為86%、45%、27%和93%。
結論：肝膽核素顯像和超聲是目前對臨床疑診為膽道閉鎖的標準成像。本研究發現這兩種工具對於膽道閉鎖的陽性預測值相對較低。因此我們認為核素顯像和超聲之間的互補性非常重要，並建議重覆進行成像以作重新評估，才作出最終的手術決定。這將有助減少膽道閉鎖的假陽性結果，從而避免不必要的手術。