Background: Biliary system ascariasis can be a rare cause of acute abdomen.

Patient report: A 70-year-old woman presented with abdominal pain for two weeks. She complained of a right upper quadrant (RUQ) pain, intermittent vomiting and weight loss. Physical examination showed RUQ and epigastric tenderness without rebound tenderness or guarding. Laboratory finding exhibited leukocytosis and mildly elevated liver enzymes.

Results: Abdominal sonography showed distended gallbladder and a tubular lesion inside the common bile duct (CBD) in favor of a parasitic lesion. A large ascaris roundworm and blood clots were extracted from the CBD by endoscopic retrograde cholangiopancreatography and sphincterotomy. After 7 days, the disease process was complicated with a subhepatic abscess formation which was managed conservatively. Finally, the patient was discharged home in fair condition after 12 days of hospitalization.

Conclusions: Ascariasis should be considered in endemic areas and early endoscopic intervention and medical therapy can be effective for extrahepatic involvement.