Validity of MDCT cholangiography in differentiating benign and malignant biliary obstruction Abstract Background: MDCT cholangiography can be utilized to identify variant biliary anatomy to guide preoperative planning of biliary surgery, and determine the cause and level of biliary obstruction. Early tumor detection and staging of biliary cancer are key factors for a possible cure by surgical resection. Between December 2019 and October 2020, 69 patients with clinically suspected biliary obstruction were enrolled in the study, subjected to clinical assessment (full history taking and clinical examination) and imaging assessment by MDCT cholangiography. Our findings were correlated to standard reference examinations including operative/ERCP/biopsy and histopathology findings. Results: The most affected age was between 60 and 70 years old, and males were more affected. The commonest clinical presentation was yellowish discoloration of the skin and sclera followed by biliary colic. Right hypochondrial tenderness was the main clinical finding on clinical examination. Our patients were categorized according to the etiology of biliary obstruction into 7 groups: malignant stricture 52.2% (36 patients), calcular 24.6% (17 patients), iatrogenic 5.8% (4 patients), portahepatis lesions 5.8% (4 patients), benign stricture 4.3% (3 patients), inflammatory 4.3% (3 patients), and congenital 1.4% (1 patient). The malignant group shows dominant mass, moderate biliary obstruction, and arterial and venous enhancement. The overall sensitivity was 94% for malignancy. Conclusion: MDCT cholangiography is non-invasive, fast, and highly sensitive and specific in the diagnosis of different causes and levels of biliary obstruction and is useful in the characterization of the lesion in cases of malignant obstruction and differentiating it from benign stricture. It can be used as an effective alternative to ERCP or PTC. Keywords: Multidetector computed tomography, Biliary obstruction, Obstructive jaundice