What is the most common cause of biliary obstruction?

• A. Cholelithiasis (gallstones)
• B. Cholangitis
• C. Biliary atresia
• D. Pancreatic tumor

Answer: (A)

Gallstones are the most frequent driver of biliary obstruction. Stones formed in the gallbladder can migrate into the common bile duct and block the flow of bile. When this happens, bile backs up in the liver, producing a cholestatic pattern: conjugated bilirubin rises, alkaline phosphatase and GGT increase, and symptoms like jaundice and dark urine can appear. Ultrasound often detects stones as echogenic foci with posterior shadowing, and more detailed biliary mapping can be done with MRCP if needed. While infections such as cholangitis can occur with obstruction and biliary atresia is a congenital cause seen in infants, gallstones remain by far the most common cause of biliary obstruction in adults. Pancreatic tumors can also compress the duct but are less common than stones.