Toxic Megacolon

Published on 09/08/2015 by admin

Filed under Radiology

Last modified 09/08/2015

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 Transverse colonic folds may be thickened (edema or hemorrhage), or lost (sloughed mucosa and submucosa)


• Colonic obstruction or Ileus

image Preservation of mucosal and transverse fold pattern


• Clostridium difficile and other infectious colitis

image Now the most common etiology
image Ulcerative colitis was more common in past


• Most severe, life-threatening complication of colitis
• Most common signs/symptoms

image Patients appear “toxic,” very ill
image Fever, pain, abdominal distension, bloody diarrhea
image Complications: Perforation, peritonitis, death
• Other signs/symptoms

image Lab data: Increased WBC and ESR; positive fecal occult blood test
• Treatment: Colectomy and treatment of complications
• Prognosis: Good following colectomy without perforation

image Poor if colonic perforation and sepsis precede colectomy
• Seen in ∼ 5% of infectious or ulcerative colitis patients


• Consider prior history of infectious or ulcerative colitis
• Dilated colon with air-fluid levels; thickened or absent transverse folds in a very sick patient
(Left) Supine radiograph in a 58-year-old woman, who presented with severe abdominal pain and bloody diarrhea, illustrates the typical appearance of toxic megacolon on plain film. The transverse colon is dilated with marked thickening of the transverse folds image.

(Right) This 35-year-old man with a history of ulcerative colitis presents with acute severe abdominal pain and distention. This supine radiograph shows a dilated, ahaustral transverse colon with a “shaggy” surface contour.
(Left) This woman developed Clostridium difficile colitis while hospitalized for other reasons. CT shows ascites image, marked dilation of the colon with loss of transverse folds, and intraluminal high-density material image representing hemorrhage and sloughed mucosa.

(Right) Axial CECT in the same case shows a generalized ileus image. The colon image is massively distended with blood and debris and its wall is relatively thin. Soon after this scan, the colon perforated and a total colectomy was required.



• Acute transmural fulminant colitis with neuromuscular degeneration and colonic dilation


General Features

• Best diagnostic clue

image Dilated ahaustral colon with pseudopolyps and air-fluid levels
• Location

image Transverse colon > other segments

Radiographic Findings

• Radiography

image Hallmark: Marked colonic dilatation with abnormal or absent fold pattern

– Transverse colon most common ± other segments
– Increased colon caliber on serial radiographs

image > 5 cm on CT, often > 8 cm (as measured on supine radiograph)
– Transverse colonic folds may be thickened (edema or hemorrhage), or lost (sloughed mucosa and submucosa)
– Mucosal islands or pseudopolyps cause irregular surface contour
– Pneumatosis coli ± pneumoperitoneum

CT Findings

• Colon distended with gas, fluid ± blood
• Distorted or absent transverse fold pattern
• Irregular nodular contour of colonic wall (mucosal pseudopolyps)
• ± intramural gas ± blood
• ± free intraperitoneal gas and fluid

Imaging Recommendations

• Best imaging tool

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