MOYNIHAN'S CATERPILLAR HUMP OF THE RIGHT HEPATIC ARTERY MIMICKING THE CYSTIC ARTERY ASSOCIATED WITH A LONG LOW ANTERIORLY INSERTING CYSTIC DUCT DURING LAPAROSCOPIC CHOLECYSTECTOMY: A POTENTIAL DOUBLE PITFALL CASE REPORT

Moynihan's caterpillar hump refers to a redundant tortuous loop of the right hepatic artery (RHA) that descends into the hepatocystic triangle, closely simulating the cystic artery in both calibre and position. We report a 35-year-old female who underwent elective laparoscopic cholecystectomy for symptomatic cholelithiasis. Intraoperatively, the RHA was found to make a tortuous anterior loop across the Hartmann's pouch before passing posterior to the cystic duct —a course highly deceptive of the cystic artery. Meticulous dissection guided by strict adherence to the Critical View of Safety (CVS) revealed a separate smaller branch arising from this looping vessel and entering the gallbladder neck as the true cystic artery. A concurrent biliary anomaly was present: the cystic duct followed a long anterior course and inserted unusually low into the common bile duct, further distorting the normal triangular anatomy. Once both structures were conclusively identified, the cystic artery and cystic duct were individually clipped and divided, and cholecystectomy was completed uneventfully. The patient was discharged on postoperative day two. This case highlights the hazard of misidentifying a caterpillar hump RHA as the cystic artery and emphasises that the co-existence of a low-inserting cystic duct multiplies the risk of inadvertent biliary or vascular injury. Strict adherence to the CVS remains the cornerstone of safe laparoscopic cholecystectomy.