What is the role of CT scanning in the workup of toxic megacolon?

Updated: Apr 03, 2019
  • Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR; Chief Editor: Eugene C Lin, MD  more...
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The large bowel appears distended, with associated fluid levels. The haustral pattern may show edema. In toxic megacolon associated with ulcerative colitis, the bowel wall may be thin. Intramural air in association with small pericolonic fluid collections may be observed. Extraluminal air may be present if a perforation is present as a complication of toxic megacolon. [21]

CT scanning provides better anatomic detail of transmural disease, mesenteric involvement, and intraperitoneal complications of inflammatory bowel disease. [21, 15] Extraluminal air associated with bowel perforation is better seen with CT than with other techniques. [1]

Distinguishing severe acute colitis from toxic megacolon is important in clinical decision making. CT is useful in distinguishing patients with toxic megacolon from patients with severe acute colitis, but not toxic megacolon as a complication. The association of air-filled colonic distension greater than 6 cm, abnormal haustral pattern, and segmental colonic parietal thinning seems pathognomonic of toxic megacolon and should lead to rapid surgery. [15]

None of the CT scan findings is specific; they may also be found in severe forms of colitides.

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