Toxic megacolon

Toxic megacolon is a complication of inflammatory bowel disease (IBD) or infectious colitis that is characterized by colonic dilatation and systemic toxicity. The diagnosis of toxic megacolon should be considered in all patients presenting with abdominal distension and acute or chronic diarrhoea. The diagnosis is clinical, based upon the finding of an enlarged dilated colon accompanied by severe systemic toxicity. The initial evaluation should be aimed at establishing the diagnosis and at determining the underlying cause. Clinical assessment is similar to that for large bowel obstruction, additionally stool specimens should be sent for culture and CDT. X-rays are important in the diagnosis. CT scanning may occasionally be of value in determining the aetiology of megacolon.

The most widely used criteria for the clinical diagnosis of toxic megacolon are:

  • Radiographic evidence of colonic distension-typical features include:

    • Dilated colon (>6cm, sometimes up to  15cm), commonly in the right or transverse colon but sometimes involving the descending colon

    • Multiple air-fluid levels in the colon with disturbance of the colonic haustrae

    • Deep mucosal ulcerations may appear as air-filled crevices between large pseudopolypoid projections extending into the colonic lumen

  • PLUS at least three of the following:

    • Fever >38ºC

    • Heart rate >120 beats/min

    • Neutrophilic leukocytosis >10,500/microL

    • Anaemia

  • PLUS at least one of the following:

    • Dehydration

    • Altered sensorium

    • Electrolyte disturbances

    • Hypotension

The main goal of treatment is to reduce the severity of colitis in order to restore normal colonic motility and decrease the likelihood of perforation. Initial treatment is medical, which is successful in preventing surgery in up to 50 percent of patients. However the surgical team should be involved early in the patient’s care.

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