Necrotizing fasciitis on CT

An axial CT scan through the lower pelvis (A) in a patient with Crohn's disease and a right hip replacement (arrowhead) shows a fistulous tract (arrow) from the rectum to the soft tissues of the right hip. Image B shows bubbles of gas in the swollen hamstring muscles (arrows) and circumferential edema of the thigh (asterisks) compared with the normal-sized left thigh. Image C is a coronal reconstruction of the thighs and exemplifies the difference in size caused by inflammatory edema (asterisk). Image D is a sagittal reconstruction and shows gas bubbles throughout the hamstring musculature (arrows).