Quantitative Analysis of Hepatobiliary Scintigraphy in Differentiating Biliary Atresia from Neonatal Hepatitis

Introduction: Neonatal cholestasis (NC) is defined as increased serum conjugated bilirubin beyond the two weeks of life. There are several causes for NC among these Biliary atresia (BA) & Neonatal Hepatitis (NH) are the two most common causes and important entities with different treatment plans and prognosis. BA requires surgical intervention whereas NH warrants medical management. Though they have similar clinical presentation, it is important to differentiate these two conditions to allow the early intervention for BA and avoid the unnecessary surgery in cases of NH. Hepatic iminodiacetic acid scintigraphy (HIDA scan) is a non-invasive functional imaging of the hepatobiliary system. The radiopharmaceutical that is used in HIDA scan follows the physiological pathway of bile excreted by the liver into bile ducts and intestine. The HIDA scan helps in differentiating the BA from NH with good diagnostic accuracy; it relies on the principle that the presence of radiotracer in the bowel confirms the patency of biliary tract and excludes the BA. Purpose of the Study: The purpose of the present study is to evaluate the sensitivity, specificity & diagnostic accuracy of HIDA scan in differentiating the BA from NH and determination of accuracy of semi quantitative parameters like LKR (Liver to kidney ratio), KLR (Kidney to liver ratio), ILR (Intestinal-liver ratio) and BLR (Background (right thigh) to liver ratio) of HIDA scan in diagnosis of BA. Material and Methods: This particular study was a retrospective study. The records of all previous HIDA scan images that had been done in infants aged between 30 and 180 days for the indication of neonatal cholestasis were re-evaluated. A total of 57 infants who had HIDA scan and histopathological proof of final diagnosis were included in the study cohort. Results: A total of 57 infants with cholestatic jaundice were studied over a period of two years between January 2023 to January 2025, among which 24 girls and 33 boys. The mean age at presentation was 69.42 ± 28.5 days (range 30 to 180 days). 32 infants had final diagnosis of BA and remaining 25 infants were diagnosed as NH on histopathological examination. In 32 infants who had final diagnosis of BA, the HIDA scan showed BA like pattern (absence of tracer excretion into bowel) in 28 infants (True positives) whereas in 25 infants who had final diagnosis of NH, the HIDA scan showed normal excretion of tracer into bowel in 19 infants (true negatives). Sensitivity, specificity and diagnostic accuracy of HIDA scan in differentiating BA from NH were 87.5%, 76% and 82.46% respectively. Positive predictive value (PPV) and Negative predictive values (NPV) are 82.35% and 82.61% respectively. Among all LKR, KLR, ILR & BLR semiquantitative parameters, ILR was the best semi-quantitative parameter with ROC (Receiver operating characteristic) curve derived an optimum cut-off value of ≤ 0.35 with sensitivity & specificity of 88.5% & 76.7% respectively for diagnosis of BA. Conclusion: According to the present study results, HIDA scan was found to be simple, safe, non-invasive, and more physiological in the evaluation of neonatal cholestatic jaundice with high diagnostic accuracy in the differentiating of BA from NH. Further use of semi-quantitative parameters while interpreting HIDA scan findings increases the specificity of the scan and decreases the false positive results. Among all semi-quantitative parameters, ILR was the optimised parameter that may improve the diagnostic performance of the HIDA scan