When Anatomy Turns Hazardous: Moynihan’s Hump as an Unexpected Challenge in Calot’s Triangle: A Case Report

Abstract

Moynihan’s or caterpillar hump is a rare anatomical variation of the right hepatic artery (RHA), characterized by a prominent tortuous arterial loop coursing close to the gallbladder, often associated with a short cystic artery. This configuration increases the risk of inadvertent vascular injury during laparoscopic cholecystectomy. We report the case of a woman in her late 40s who presented with acute calculous cholecystitis. She was managed initially with intravenous fluids and antibiotics, followed by an interval laparoscopic cholecystectomy after six weeks. Intraoperatively, a large pulsatile artery running parallel to the cystic duct was identified and confirmed as Moynihan’s hump, with a short cystic artery arising from the distal loop. Careful dissection and controlled clipping allowed safe completion of the procedure without vascular injury. The patient had an uneventful recovery and remained asymptomatic at a 2-month follow-up. This case underscores the importance of preoperative vigilance, meticulous intraoperative dissection, and the achievement of the critical view of safety to avoid potentially catastrophic complications associated with this rare vascular anomaly.