Figure 6a. Duodenal perforation after ERCP in a 49-year-old woman. ERCP was performed for evaluation of right upper quadrant pain and revealed a stricture in the common bile duct and nonfilling of the gallbladder, findings compatible with acute cholecystitis. The patient had pain immediately after the procedure and a significant amount of free air. CT was performed without contrast material on the day of ERCP. (a) CT scan obtained with a soft-tissue window shows free air (*) diffusely in the peritoneal cavity, retroperitoneum, and subcutaneous tissues. (b) CT scan obtained inferior to a shows extensive free air in the root of the mesentery (arrow). Air also dissected superiorly into the mediastinum and right pleural cavity. (c) Follow-up CT scan obtained 2 days later at the same level as in a shows a significant decrease in the amount of free air (*). There is thickening of the wall of the gallbladder (arrow) due to cholecystitis. The patient recovered within a few days with conservative treatment.