Diagnostic Accuracy of Ultrasonography for Diagnosing Common Bile Duct Dilation Taking Magnetic Resonance Cholangiopancreatography as Gold Standard

Background: CBD is a significant initial radiological sign of biliary obstruction and is important in determining subsequent diagnostic tests. Transabdominal ultrasonography is extensively utilized as a primary imaging modality, with MRCP being utilized to offer more definitive evaluation. The purpose of this study was to establish the diagnostic accuracy of transabdominal ultrasonography in identifying CBD dilatation with MRCP as the reference. Methods: This cross-sectional validation study was carried out in the Radiology department of Islamabad Diagnostic Centre (IDC), Islamabad from 01st February 2024 to 30th August 2024. A total of 180 patients between 20 and 80 years of age with clinical suspicion of obstructive jaundice or choledocholithiasis were included. All patients were referred from gastroenterology department and ultrasound and MRCP scanning was done within 72 hours. The diagnostic accuracy of ultrasound in terms of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall diagnostic accuracy were calculated keeping findings of MRCP as a gold standard. Results: The mean age of the study population was 50.67 ± 12.77 years. Female patients were 51.1% of total study subjects. The prevalence of common bile duct dilatation on ultrasonography was 50 (27.8%) and it was 42 (23.3%) on MRCP which was used as the gold standard. Data analysis showed that the sensitivity, specificity, positive predictive value, negative predictive value and the overall diagnostic performance for detection of common bile duct dilatation of ultrasonography was 83.3%, 89.1%, 70.0%, 94.6% and 87.8% respectively. Conclusion: Transabdominal ultrasonography turned out to be a highly effective and precise diagnostic tool in the case of detecting CBD dilatation compared to MRCP and can be implemented as a first-line screening option in patients with suspected biliary pathology. Its negative predictive value and high specificity allow it to be especially useful when it comes to ruling out significant ductal dilatation, and informing further imaging decision-making.