Biliary ascariasis is a disease in which roundworms enter the bile duct from the small intestine in a retrograde manner, causing spasms in the bile duct and the sphincter of Oddi. The main clinical feature is the sudden onset of upper abdominal pain in patients. After entering the bile duct, most roundworms stay in the common bile duct. Because the angle between the cystic duct and the common bile duct is large, roundworms rarely enter the gallbladder, but can drill into the left and right hepatic bile ducts. It is more common in children and young people, with no gender difference, and is more common in rural areas. Improper treatment can cause a variety of complications and great harm, and is also one of the causes of primary bile duct stones.