toxic megacolon

Etiology

• colitis
  • inflammatory bowel disease (ulcerative colitis)
  • pseudomembranous colitis (C difficile colitis)
  • Cytomegalovirus in AIDS patients
  • Salmonella, Shigella, Campylobacter, enterohemorrhagic E coli 0157, Entamoeba
• precipitants
  • hypokalemia
  • antimotility agents, opiates, anticholinergics, antidepressants
  • barium enema
  • colonoscopy & bowel preparation

Pathology

• chemical mediators such as nitric oxide & interleukins may play a pivotal role in the pathogenesis

Clinical manifestations

• tachycardia
• fever
• hypotension (shock)
• abdominal pain & tenderness
• abdominal distension
• decreased or absent bowel sounds
• bloody diarrhea

Laboratory

• complete blood count (CBC)
  • leukocytosis (neutrophilia)

Diagnostic procedures

• colonoscopy is contraindicated (increased risk of perforation)

Radiology

• abdominal X-ray
  • colectomy indicated without CT if diagnosis evident
  • colonic dilation > 5.5 cm with systemic toxicity
• computed tomography of the abdomen

Complications

• colonic perforation
  • mortality 40% with emergency surgery

Differential diagnosis

• Hirschsprung disease
• acquired megacolon
• colonic pseudo-obstruction (Ogilvie syndrome)
• diffuse gastrointestinal dysmotility

Management

• supportive care
  • intravenous fluids
  • high-dose glucocorticoids
  • broad-spectrum antibiotics
    • 3rd generation cephalosporin + metronidazole
• treatment of the underlying colitis
  • oral vancomycin + intravenous metronidazole for C difficile colitis
• colonic decompression via tube drainage or positional techniques
• surgical consultation
  • subtotal colectomy with ileostomy & either Hartmann pouch, sigmoidostomy, or rectostomy (generally procedure of choice)

More general terms

• megacolon