EP.TH.665Where’s the gallbladder? A rare case of gallbladder agenesis with cystic duct stone

Aims Gallbladder agenesis is a rare congenital anatomical malformation with an incidence of 0.007-0.0027%. Although usually asymptomatic, clinically it may present similarly to biliary colic. There may be increased risk of de novo biliary duct stone formation due to biliary dyskinesia, subsequent duct dilatation and biliary stasis. We present a case of incidental gallbladder agenesis identified during intended laparoscopic cholecystectomy. Methods A 68 year-old female with no significant comorbidities presented with a 16 hour history of colicky right upper quadrant pain and vomiting. She had been awaiting cholecystectomy for increasingly symptomatic gallstones, most recently visualised within a contracted gallbladder on ultrasound two months prior. Recurrently obstructive LFT’s warranted urgent magnetic resonance cholangiopancreatography (MRCP), which identified a poorly-visualised contracted gallbladder and a 10mm common bile duct without filling defect. At index laparoscopic cholecystectomy, a very small thick-walled structure resembling the gallbladder was identified and safely excised in retrograde; a stone was seen within. Results Macroscopic examination revealed a 27 x 9 x 11mm piece of dark brown tissue containing soft orange material. Microscopic histological examination confirmed this to be cystic duct focally lined by mucinous epithelium with chronic inflammation. Findings were consistent with gallbladder agenesis. Conclusions Although rare, it is important for surgeons to maintain an index of suspicion for gallbladder agenesis, particularly if repeated imaging demonstrates a poorly-visualised or ‘contracted’ gallbladder despite adequate fasting. Furthermore, as in this case, the presence of ‘gallbladder’ stones radiologically does not preclude gallbladder agenesis. Anticipation of this malformation may aid interpretation of biliary anatomy, if incidentally found intra-operatively.