Figure 24b. Gastrocutaneous and colocutaneous fistulas. (a) Transverse contrast-enhanced CT scan in a 65-year-old woman with Crohn disease shows unsuspected gastrocutaneous fistula (F). Note soft-tissue thickening (arrowheads) of the abdominal wall and stomach. A focal abdominal bulge was initially thought at clinical examination to be a ventral hernia because overlying skin was still intact at that time. (b) Transverse contrast-enhanced CT scan in a 78-year-old man who had previously undergone surgery for abdominal wall abscess shows enteric contrast agent (arrow) outlining a colocutaneous fistula involving the sigmoid colon (S) and an abdominal wound. Diverticulitis was the underlying cause for both the original abscess and recurrent fistula.