CT of abdominal abscess with fistulous communication to the gastrointestinal tract.

We review CT of 24 cases of intraabdominal abscess with fistulous communication to the GI tract confirmed by GI contrast study or fistulogram. Underlying causes of fistulization included recent GI tract surgery (13), diverticulitis (four), unknown etiology (three), malignant neoplasm (two), trauma (one), and pancreatitis (one). Thirteen (54%) abscesses showed air-fluid levels, 14 (58%) showed air bubbles, and seven (29%) showed both. Bowel contrast material was administered in 21 cases, and optimal bowel opacification was effected in 16. However, contrast extravasation into the abscess was noted in only six cases. We conclude that an air-fluid level may indicate the presence of a fistulous communication to the GI tract, but its absence does not necessarily mean there is no communication. Also, recognition of contrast within the abscess is uncommon even with optimal bowel opacification. In cases of clinical suspicion of internal fistula, a fistulogram or GI contrast study should be performed.