Toxic Megacolon

Published on 09/08/2015 by admin

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Last modified 22/04/2025

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

TOP DIFFERENTIAL DIAGNOSES

• Colonic obstruction or Ileus

Preservation of mucosal and transverse fold pattern

PATHOLOGY

• Clostridium difficile and other infectious colitis

Now the most common etiology

Ulcerative colitis was more common in past

CLINICAL ISSUES

• Most severe, life-threatening complication of colitis

• Most common signs/symptoms

Patients appear “toxic,” very ill

Fever, pain, abdominal distension, bloody diarrhea

Complications: Perforation, peritonitis, death

• Other signs/symptoms

Lab data: Increased WBC and ESR; positive fecal occult blood test

• Treatment: Colectomy and treatment of complications

• Prognosis: Good following colectomy without perforation

Poor if colonic perforation and sepsis precede colectomy

• Seen in ∼ 5% of infectious or ulcerative colitis patients

DIAGNOSTIC CHECKLIST

• 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 .

(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 .

(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 , marked dilation of the colon with loss of transverse folds, and intraluminal high-density material representing hemorrhage and sloughed mucosa.

(Left) This woman developed Clostridium difficile colitis while hospitalized for other reasons. CT shows ascites , marked dilation of the colon with loss of transverse folds, and intraluminal high-density material representing hemorrhage and sloughed mucosa.

(Right) Axial CECT in the same case shows a generalized ileus . The colon 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.

(Right) Axial CECT in the same case shows a generalized ileus . The colon 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.

TERMINOLOGY

Definitions

• Acute transmural fulminant colitis with neuromuscular degeneration and colonic dilation

IMAGING

General Features

• Best diagnostic clue

Dilated ahaustral colon with pseudopolyps and air-fluid levels

• Location

Transverse colon > other segments

Radiographic Findings

• Radiography

Hallmark: Marked colonic dilatation with abnormal or absent fold pattern

– Transverse colon most common ± other segments

– Increased colon caliber on serial radiographs

> 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

CECT with multiplanar reformations

DIFFERENTIAL DIAGNOSIS

Colonic Obstruction

• Gas- and stool-filled colon to point of obstruction

• Retained transverse fold and mucosal patterns excludes toxic megacolon

Adynamic or Paralytic Ileus

• Dilated small and large bowel without transition point

• Normal transverse fold pattern excludes toxic megacolon

PATHOLOGY

General Features

• Etiology

Clostridium difficile and other infectious colitis

– Now the most common etiology

– Ulcerative (and granulomatous) colitis had been more common in past

Amebiasis, strongyloidiasis, bacillary dysentery

Typhoid fever, cholera, Behçet syndrome

Gross Pathologic & Surgical Features

• Colon is grossly dilated with fluid and gas

• Wall may appear thinned or thick

• Hemorrhagic necrosis of colonic mucosa and submucosa

May extend into or through serosa

CLINICAL ISSUES

Presentation

• Most common signs/symptoms

Patients appear “toxic,” very ill

Fever, pain, tenderness, abdominal distension, bloody diarrhea

Hypotension, sepsis, shock

• Other signs/symptoms

Lab data: Increased WBC and ESR

Demographics

• Age

Any age for infectious colitis patients

– 20-35 years for ulcerative colitis patients

• Gender

M = F

• Epidemiology

Seen in ∼ 5% of patients with infectious or ulcerative colitis

– Medical and surgical mortality: > 20%

– Most severe, life-threatening complication of colitis

Natural History & Prognosis

• For infectious colitis

Delayed diagnosis or failed antibiotic therapy may result in toxic megacolon

• For ulcerative colitis, predisposing factors

Endoscopy; use of opiates and anticholinergic drugs

• Complications: Perforation, peritonitis, death

• Prognosis: Good following colectomy without perforation

Poor if colonic perforation and sepsis precede colectomy

Treatment

• Colectomy; treat complications

DIAGNOSTIC CHECKLIST

Consider

• Prior history of infectious or ulcerative colitis

Image Interpretation Pearls

• Dilated colon with air-fluid levels; thickened or absent transverse folds in a very sick patient

(Left) This 68-year-old woman has longstanding Crohn (granulomatous) colitis with acute exacerbation. This supine film shows marked dilation of the transverse colon with a featureless ahaustral appearance. There is some irregularity of the luminal surface , suggesting mucosal sloughing or pseudopolyps.

(Left) This 68-year-old woman has longstanding Crohn (granulomatous) colitis with acute exacerbation. This supine film shows marked dilation of the transverse colon with a featureless ahaustral appearance. There is some irregularity of the luminal surface , suggesting mucosal sloughing or pseudopolyps.

(Right) Axial CECT in the same patient shows the colonic dilation and ahaustral appearance with marked thinning of the wall, which suggests a risk of perforation.

(Left) A magnified view of the same CT section shows tags of inflamed mucosa or pseudopolyps within the dilated, thin-walled transverse colon.

(Left) A magnified view of the same CT section shows tags of inflamed mucosa or pseudopolyps within the dilated, thin-walled transverse colon.

(Right) Another CT section in the same patient shows fluid , distention and thinning of the walls of the colon, as well as more mucosal pseudopolyps .

(Right) Another CT section in the same patient shows fluid , distention and thinning of the walls of the colon, as well as more mucosal pseudopolyps .

(Left) Axial CECT in the same patient shows similar involvement of the rectosigmoid colon . Because of symptoms that were refractory to medical management, as well as these CT findings, the patient had a total colectomy.

(Left) Axial CECT in the same patient shows similar involvement of the rectosigmoid colon . Because of symptoms that were refractory to medical management, as well as these CT findings, the patient had a total colectomy.

(Right) Gross pathology photograph from a similar patient who underwent colectomy illustrates hemorrhagic necrosis of the colonic mucosa and pseudopolyps in a case of toxic megacolon.

(Right) Gross pathology photograph from a similar patient who underwent colectomy illustrates hemorrhagic necrosis of the colonic mucosa and pseudopolyps in a case of toxic megacolon.

(Left) This 61-year-old man was hospitalized for unrelated reasons and developed acute pain, diarrhea, hypotension, and tachycardia. This supine film shows bulging flanks due to ascites. The colon is diffusely dilated with a loss of the normal transverse fold pattern. The folds that are seen are grossly thickened and have a “thumbprint” appearance .

(Left) This 61-year-old man was hospitalized for unrelated reasons and developed acute pain, diarrhea, hypotension, and tachycardia. This supine film shows bulging flanks due to ascites. The colon is diffusely dilated with a loss of the normal transverse fold pattern. The folds that are seen are grossly thickened and have a “thumbprint” appearance .

(Right) Axial CECT in the same patient shows ascites and colonic distension .

(Right) Axial CECT in the same patient shows ascites and colonic distension .

(Left) Another CT section in the same patient shows that the colon is distended with gas and fluid to a diameter of 7 cm. The mucosa is hyperenhancing and the wall is thickened by submucosal edema . No normal transverse folds are evident. Ascites fills the paracolic gutters , accounting for the bulging flanks seen on plain films.

(Left) Another CT section in the same patient shows that the colon is distended with gas and fluid to a diameter of 7 cm. The mucosa is hyperenhancing and the wall is thickened by submucosal edema . No normal transverse folds are evident. Ascites fills the paracolic gutters , accounting for the bulging flanks seen on plain films.

(Right) Pelvic CT section in the same patient shows marked fluid distention and wall thickening of the rectosigmoid colon .

(Right) Pelvic CT section in the same patient shows marked fluid distention and wall thickening of the rectosigmoid colon .

(Left) Coronal reformatted CT section in the same patient shows the markedly distended sigmoid colon with a complete loss of its normal transverse fold pattern.

(Left) Coronal reformatted CT section in the same patient shows the markedly distended sigmoid colon with a complete loss of its normal transverse fold pattern.

(Right) Another CT section in the same patient confirms the pancolitis and ascites . These CT and clinical features are classic for toxic megacolon due to infectious colitis (C. difficile), confirmed at urgent colectomy. The colonic mucosa showed extensive necrosis and sloughing, but no frank perforation was found.

(Right) Another CT section in the same patient confirms the pancolitis and ascites . These CT and clinical features are classic for toxic megacolon due to infectious colitis (C. difficile), confirmed at urgent colectomy. The colonic mucosa showed extensive necrosis and sloughing, but no frank perforation was found.

Anteroposterior radiograph shows the typical appearance of toxic megacolon with diffuse colonic distention, especially transverse and descending, and the suggestion of wall thickening due to subserosal and omental edema.

Anteroposterior radiograph shows the typical appearance of toxic megacolon with diffuse colonic distention, especially transverse and descending, and the suggestion of wall thickening due to subserosal and omental edema.

Anteroposterior radiograph shows severe and classic toxic megacolon. Note the colonic distention, especially transverse, and the suggestion of pseudopolyps .

Anteroposterior radiograph shows severe and classic toxic megacolon. Note the colonic distention, especially transverse, and the suggestion of pseudopolyps .

Anteroposterior CECT demonstrates the typical appearance of toxic megacolon on plain film. Note the diffuse colonic dilatation with marked thumbprinting .

Anteroposterior CECT demonstrates the typical appearance of toxic megacolon on plain film. Note the diffuse colonic dilatation with marked thumbprinting .

Anteroposterior radiograph of supine abdomen demonstrates marked dilatation of transverse colon with a scalloped contour indicating edematous mucosa.

Anteroposterior radiograph of supine abdomen demonstrates marked dilatation of transverse colon with a scalloped contour indicating edematous mucosa.

Anteroposterior radiograph of transverse colon in a patient with ulcerative colitis shows a variant appearance of toxic megacolon. The colon is ahaustral but without pseudopolyps typically seen in toxic megacolon.

Supine radiograph shows diffusely dilated bowel in an acutely ill patient with ulcerative colitis. The transverse colon is dilated and ahaustral with an irregular mucosal surface.

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