When biliary-gastric fistula mimics double gallbladder: a diagnostic challenge in acute cholecystitis

Cholecystoenteric fistulas occur in 3%-5% of patients with gallbladder disease and can create complex imaging appearances that mimic anatomical variants. Biliary-gastric fistulas are particularly rare, representing only 15% of cholecystoenteric fistulas. We report a 76-year-old male with chronic hepatic colic. Initial imaging suggested possible gallbladder malignancy with apparent double gallbladder anatomy. Magnetic resonance cholangiography revealed two distinct formations suggesting double gallbladder with single cystic duct. However, surgical exploration disclosed acute cholecystitis complicated by biliary-gastric fistula creating a pseudocystic formation that mimicked the second gallbladder. Laparoscopic approach was converted to open cholecystectomy due to severe inflammation. Histopathology confirmed benign inflammatory disease without malignancy. This case illustrates how cholecystoenteric fistulas can create imaging appearances mimicking anatomical variants such as double gallbladder. Accurate preoperative diagnosis remains challenging, emphasizing the importance of surgical exploration in complex inflammatory conditions.