Uncommon Presentation of Xanthogranulomatous Cholecystitis in a True Gallbladder Diverticulum: A Case Report and Literature Review.

BACKGROUND The gallbladder develops from the hepatic diverticulum during the fourth week of gestation, which also give rise to the liver, extrahepatic biliary ducts, and ventral part of the pancreas. Infrequently, the gallbladder has malformation or disruption in embryogenesis, leading to congenital anomalies. There are various congenital anomalies that can arise in the gallbladder. True or congenital diverticulum of the gallbladder is a rare entity that accounts for only 0.06% of gallbladder congenital anomalies and 0.0008% of cholecystectomies at the Mayo Clinic. CASE REPORT Herein, we report a rare case of a 38-year-old woman who presented to Jubail General Hospital's surgery clinic with right upper-quadrant (RUQ) pain associated with vomiting after meals for 1 month. Laparoscopic cholecystectomy was done and gallbladder tissue was sent to histopathology. Gross examination revealed an outpouching mucosa within the wall that was proven to consist of muscularis and serosa layers under light microscope. Interestingly, xanthogranulomatous inflammation was confined to the diverticulum, unlike the chronic inflammation involving the remaining gallbladder. Based on the above findings, the diagnosis of congenital diverticulum with xanthogranulomatous cholecystitis was made. CONCLUSIONS Gallbladders associated with a true diverticulum are uncommonly found to be buried in the liver, leading to surgical difficulties during cholecystectomy. Therefore, background knowledge of occasional anomalies plays a crucial role in guiding the surgeon to choose the optimal method of management. We also discuss the associated complications that accompany these anomalies, such as non-specific prolonged ailments, acalculous cholecystitis, cholecystitis and cholelithiasis, recurrent cholangitis, and carcinoma of the gallbladder.