Toxic megacolon

total or segmental nonobstructive colonic dilatation plus systemic toxicity

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

• Radiographic evidence of colonic distension
• PLUS at least three of the following:

• Fever >38ºC
• Heart rate >120 beats/min
• Neutrophilic leukocytosis >10,500/microL
• Anemia
• PLUS at least one of the following:
• Dehydration
• Altered sensorium
• Electrolyte disturbances- Metabolic alkalosis secondary to volume depletion and potassium loss is associated with a poor prognosis. Metabolic acidosis suggests the presence of ischemic colitis.
• Hypotension

non toxic- congenital megacolon (Hirschsprung's disease), idiopathic or acquired megacolon occurring with chronic constipation of any etiology, and intestinal pseudoobstruction





mucosal inflammation leads sequentially to the release of inflammatory mediators and bacterial products, increased inducible nitric oxide synthase, generation of excessive nitric oxide, and colonic dilatation.

extent of dilatation appears to be correlated with the depth of inflammation and ulceration. Damage to the myenteric plexus.

These include hypokalemia, antimotility agents, opiates, anticholinergics, antidepressants, barium enema, and colonoscopy. Discontinuing or rapid tapering of corticosteroids, sulfasalazine, or 5-ASA compounds also may contribute to the development of megacolon

Knowledge of prior attacks of IBD, the extent and type of disease, details of prior therapy, extraintestinal manifestations of IBD, recent travel, occupational exposure (eg, day care workers), antibiotic or chemotherapy use, use of antimotility agents, and HIV/AIDS status are very helpful

Radiography — Plain abdominal radiographs

• The transverse or right colon is usually the most dilated, frequently greater than 6 cm and occasionally up to 15 cm on supine films . Repositioning  results in redistribution of air in the colon,
• Multiple air-fluid levels, colonic haustral pattern is either absent or severely disturbed.
• Deep mucosal ulcerations may appear as air-filled crevices 

 only for mecanical obstruction- Barium enema or colonoscopy is often required to diagnose the level and type of obstruction.
-diarrhea is unusual and air is absent in the colon below the point of obstruction.

High resolution ultrasonography can be used to accurately determine the extent and activity of severe ulcerative colitis and assess the response to therapy; it may also permit the early detection of toxic megacolon .

CT can determinie the etiology of megacolon. -diffuse colonic thickening
- useful in patients with AIDS who may have several intercurrent intraabdominal processes.
- identify complications of megacolon, such as perforation or vascular compromise

Limited endoscopy without bowel preparation is useful if IBD has not previously been diagnosed or an infective process is suspected, particularly CMV or acute bacillary dysentery. 

full colonoscopy is extremely risky

medical treatment- preventing surgery in up to 50 percent of patients. However, a surgical consultation should be obtained upon admission,

- bowel rest and a nasogastric tube (or long intestinal tube)  to decompress the gastrointestinal tract. Enteral feeding if patient shows signs of improvement to hasten mucosal healing and stimulate normal motility.
- ICU. Complete blood counts, electrolytes, and serial abdominal plain films are reviewed every 12 hours initially and then daily as the patient improves. Anemia, dehydration, and electrolyte deficits, particularly hypokalemia, may aggravate colonic dysmotility and should be treated aggressively.

(TPN) is of limited value

All antimotility agents, opiates, and anticholinergics should be discontinued.

prophylaxis for both gastric stress ulcerations and deep venous thrombosis (pneumatic compression stockings).

Antibiotic to reduce septic complications and in anticipation of peritonitis from perforation. We generally use ampicillin-gentamicin-metronidazole or a third-generation cephalosporin with metronidazole.

 Intravenous corticosteroids (hydrocortisone 100 mg or equivalent every six to eight hours or by continuous infusion) - ulcerative colitis or Crohn's disease; this does not increase the risk of perforation .  dexamethasone has been shown in experimental studies to decrease the colonic diameter by diminishing the expression of inducible NO synthase. methylprednisolone - its lower sodium retaining and potassium wasting properties, while others prefer prednisolone since the parenteral dose is equal to the oral dose. Steroids are not used in toxic megacolon due to C. difficile colitis or infective colitis.

Sulfasalazine and 5-ASA compounds have no role in patients with toxic megacolon due to IBD and should be initiated only after the attack begins to resolve.

Cyclosporine is useful in the treatment of severe colitis refractory to steroid therapy, but the experience in toxic megacolon is limited.

Some authors recommend intermittent rolling maneuvers or the knee-elbow position to help redistribute gas in the colon and thereby promote decompression- in patient not toxic

 persistent fever after 48 to 72 hours of steroid therapy should raise the possibility of localized perforation or abscess.

 Free perforation, massive hemorrhage, increasing transfusion requirements, worsening signs of toxicity, and progression of colonic dilatation are absolute indications for surgery.

surgical studies recommend colectomy if there is persistent colonic distention after 48 to 72 hours. However, we recommend prolongation of medical therapy up to seven days if the patient appears to be clinically improving despite persistent megacolon and there is no perforation

- severe C. difficile colitis, the first step is to stop the offending antibiotic, followed by vancomycin 500 mg four times daily orally or via a nasogastric tube NOT IV and intravenous metronidazole at a dose of 500 mg every eight hours. Fecal concentrations of metronidazole in the therapeutic range are achieved with this regimen because of biliary excretion of the drug.

Surgery — Subtotal colectomy with end-ileostomy - lower morbidity and mortality than single stage proctocolectomy and allows subsequent re-anastomosis. Early surgery without perforation results has much lower mortality than after perforation (8 VS 40 %)