Diverticulitis
- Diverticula are identified on CT scans as outpouchings of the colonic wall. They may contain air, barium, or fecal material.
- The diagnosis of diverticulitis by using CT scans is based on the detection of colonic and paracolic inflammation in the presence of underlying diverticula.
- Linear stranding in the fat of the root of the sigmoid mesentery is a common finding in patients with diverticulitis.
- The appearance of diverticulitis may vary from minimal stranding of the mesenteric fat and small extraluminal collections of fluid or air in mild cases to extensive stranding and increased attenuation of the fat along with fistulas or large abscesses in more severe cases.
- Symmetric thickening of the colonic of approximately 4-5 mm is common.
- Enhancement of the colonic wall is commonly noted. This usually has inner and outer high-attenuation layers, with a thick middle layer of low attenuation.
- Small fluid collections in the colon wall may be present and represent intramural abscesses.
- Free diverticular perforation results in the extravasation of air and fluid into the pelvis and peritoneal cavity.
- Peritoneal fluid containing air bubbles may be seen, often adjacent to the sigmoid colon. These findings indicate peritonitis caused by free perforation of a diverticulum.
- On CT scans, fistulas and sinus tracts appear as linear or branching structures in the pericolic fat.
- Fistulas may communicate with an abscess or another hollow viscus, most commonly the bladder.