Large Bowel

CT colonography (virtual colonoscopy). 3-D endoluminal and 2-D axial CT images shown in parallel for same colonic lesion. Images demonstrate the importance of comparing both images for determining extent of identified lesions. Endoluminal view shows intraluminal part of lesion only, while the axial image demonstrates serosal extension of the lesion allowing for more accurate staging (arrows). [Courtesy of Dr. N. Jaffer]

Represents a stenosed featureless colon.
The differential diagnosis for this includes:

1. Long standing (burnt out) ulcerative colitis
2. Granulomatous colitis
3. Unused bowel (bypassed colon with ileostomy)
4. Cathartic bowel (rare – usually right colon, spares rectum)
5. Colonic amyloidosis
6. Scleroderma

Colon appears like a smooth tube due to loss of haustrations; ileocecal valve widely patent with involvment of terminal ileum.

LLD abdominal radiograph showing extreme dilatation of the transverse colon. [Courtesy Dr. N. Jaffer]

Volvulus – Bird-beak sign
Contrast enhanced study illustrating the “bird-beak” sign associated with cecal volvulus. [Courtesy of Dr. N. Jaffer]

This patient had sigmoid volvulus.

Axial CT image of large bowel obstruction secondary to large intraluminal sigmoid mass. [Courtesy of Dr. N. Jaffer]

Dilated loop of colon (>6 cm) with visible haustra. [Courtesy of Dr. N. Jaffer]

Ischemia – Thumb-printing sign
The above images demonstrate the “thumb-printing” sign typical of colonic ischemia. It is most notable in the transverse colon on the left image, and the transverse and descending colon on the right image. [Courtesy of Dr. N. Jaffer]

Mucosal and submucosal herniations through muscular layer of bowel. [Courtesy of Dr. G. Olscamp]