Intra-abdominal abscesses are most often the sequelae of gastrointestinal or biliary surgery, diverticulitis, and Crohn’s disease. In the appropriate clinical setting, a focal fluid collection that demonstrates rim enhancement on gadolinium-enhanced images suggests the correct diagnosis.
The addition of fat suppression and image acquisition 2–10 min after injection (interstitial phase) can highlight the enhancement of the abscess wall and surrounding tissues. Layering of lower-signal-intensity debris in the dependent portion of the cystic lesion on T2-weighted images is a common finding in abscesses reflecting the layering of high protein content dependently in abscesses. This is a very specific finding for abscess.
When air is identified within a fluid collection, active infection, and/or fistula to the bowel is present. The combination of breathing independent T2-weighted echo-train spin-echo, gadolinium-enhanced capillary-phase T1- weighted gradient-echo, interstitial-phase fat-suppressed gradient-echo, and multiplanar imaging, render MRI a very accurate technique for detecting intraperitoneal abscesses. MRI may be the technique of choice in patients who have dense intraluminal barium contrast, renal failure, or allergy to iodine (Noone et al. 1998).