Figure 6a. Gallbladder perforation with an enterobiliary fistula in a 68-year-old man with right upper quadrant pain and a high fever. MR imaging was performed to search for the cause of gas in the gallbladder lumen seen at US and CT. (a) Axial heavily T2-weighted image shows a distorted gallbladder. Intraluminal gas (*) forms an upper layer and purulent bile (arrow) forms a lower layer of low signal intensity. Note the irregular thick gallbladder wall with a hyperintense focus (arrowhead), which represents a small ulcerative projection. (b) Axial fat-suppressed T2-weighted image shows the intraluminal gas (*) in the gallbladder, which has a diffuse thick hyperintense wall. There is a tiny gas bubble in the ulcerative projection (arrowhead). (c) Axial contrast-enhanced fat-suppressed T1-weighted image shows that the left gallbladder wall has an irregular contour with inhomogeneous intense enhancement (arrowhead), an appearance suggestive of gallbladder perforation. Note the decreased enhancement of the right gallbladder wall (arrows), a finding suggestive of ischemic change and gangrene. A subsequent gastroduodenal barium study and surgery demonstrated a cholecystoduodenal fistula.