Figure 4d. Acute gangrenous cholecystitis due to an impacted calculus in a 70-year-old man with right upper quadrant pain and a high fever. MR imaging was performed because US and CT findings were inconclusive in regard to the severe symptoms. (a, b) Axial fat-suppressed T2-weighted (a) and fat-suppressed T1-weighted (b) images show irregular thickening of the gallbladder wall with small areas of high signal intensity (arrowheads). The hyperintense bile on the fat-suppressed T1-weighted image (b) is suggestive of concentrated bile. (c) Axial contrast-enhanced fat-suppressed T1-weighted image shows inhomogeneous enhancement of the irregularly thickened gallbladder wall and lack of enhancement at the fundus (arrow). (d) Sagittal contrast-enhanced fat-suppressed T1-weighted image shows that the mucosal layer is disrupted at the gallbladder fundus and body (arrows). MR cholangiopancreatography showed an impacted calculus in the gallbladder neck.