S3485 Anatomical Variant of the Cystic Duct Arising From the Ampulla

Introduction: Variations in biliary anatomy, detected most commonly as incidental findings, are well documented in the literature, with multiple references to anatomic variations in the insertion of the cystic duct into the common hepatic duct, either directly above or within the pancreas. These anomalies may lead to clinical symptoms due to biliary obstruction or dysfunction. This case describes a rare variant in which the cystic duct, rather than joining the common hepatic duct proximally, directly connects to the ampulla, creating compression on the common bile duct (CBD), mimicking features of sphincter of Oddi dysfunction (SOD). This variant is significant, as it has never been described in the literature previously. Nonetheless, it can lead to recurrent biliary colic, post-cholecystectomy syndrome, and difficulties in biliary interventions. Case Description/Methods: A 30-year-old man with past medical history of substance use disorder and asthma presented to the gastroenterology clinic for evaluation of persistent abdominal pain. The patient had undergone cholecystectomy in July 2021 and reported ongoing nausea, vomiting, and epigastric pain since the surgery. A HIDA scan with cholecystokinin (CCK) stimulation revealed a positive score of 7, suggesting SOD. An abdominal computed tomography scan raised concerns for a possible micro-esophageal perforation, but the patient was asymptomatic. Due to persistent symptoms, the patient underwent endoscopic retrograde cholangiopancreatography (ERCP), which revealed a rare anatomical variant of the biliary system. Contrast injection demonstrated the presence of 3 ducts- the CBD, pancreatic duct, and cystic duct- all draining directly into the ampulla. A balloon occlusion technique confirmed that the cystic duct was inserting directly into the ampulla and compressing the CBD, leading to biliary outflow obstruction. A biliary sphincterotomy was performed, and 2 plastic biliary stents were placed to alleviate obstruction. The patient tolerated the procedure well and had significant symptom relief post-ERCP. Discussion: This case highlights a rare biliary anatomical variation where the cystic duct inserted directly into the ampulla, leading to CBD compression and recurrent biliary symptoms. Recognition of such anomalies is critical for proper diagnosis and management, particularly in post-cholecystectomy patients with persistent pain. ERCP remains a valuable tool in both diagnosis and intervention for these rare anatomical findings.