RADIOLOGY: GASTROINTESTINAL: GI: Case# 32847: DIVERTICULAR ABSCESS. This is a 75 year old female with a history of autoimmune hepatitis. She has a pre-pyloric mass by endoscopy. We are requested to evaluate for the pre-pyloric mass as well as for abscess. Multiple diverticula are present in the colon, particularly in the region of the sigmoid. There is extra-luminal fluid with a gas fluid level and surrounding inflammatory changes immediately adjacent to the sigmoid colon. CT has been shown to be capable of detecting the presence of diverticulitis, confirming the existence of fistulae, and in determining the presence and location of pericolic abscesses. The visualization of an inflammatory process in the pericolic fat is the primary diagnostic feature of diverticulitis. Most diverticula occur along the messenteric surface of the colon. Thus, perforation due to diverticulitis is initially confined to between the leaves of the mesocolon. CT is superior to barium enema in the documentation of this extraluminal disease. DIverticula are seen on CT as small rounded collections of air, feces, or contrast material outside of the lumen. Diverticulitis is also associated with thickening of the colon wall (>5mm). Other findings include pericolic inflammatory soft tissue mass often containing fluid, air, contrast, or fecal material; linear stranding densities in pericolic fat representing inflammatory changes; sinus tracts and fistulae to adjacent organs or skin represented by linear fluid or air connections. Diverticulitis can be associated with the formation of an extensive abscess. Bowel and urinary tract obstruction as a result of inflammation are not uncommon.