Toxic megacolon

Background

Average inner diameters and ranges of different sections of the large intestine.

• Colonic Dilation ≥6cm
• Therapy: Fluids, Electrolyte Repletion, Steroids, Antibiotics, Surgical Consultation
• AVOID anticholingerics, anti-motility agents, opioids

Causes

• Most commonly IBD (Ulcerative Colitis >>> Crohn's disease)
• Bacterial (Salmonella, Shigella, Campylobacter, C. Diff, Yersinia, E. Coli)
• Viral (CMV, Rotavirus)
• Fungal/Protozoa (Aspergillus, Entamoeba, Cryptosporidium)
• Drugs (Anti-motility agents, anticholinergics, opioids)
• Less Common Causes (Ischemic Colitis, Collagenous Colitis, Obstructive Colorectal Cancer, Colonic Lymphoma, Kaposi's Sarcoma, Chemotherapy)
• Pediatric Population (Hirschsprung's Disease, Hemolytic Uremic Syndrome)
• HIV/AIDS Population (CMV, C. Diff)

Clinical Features

• Abdominal Pain ± Distention
• Fever
• Tachycardia
• Diarrhea, ± Bloody
• Hypotension
• Altered Mental Status (AMS)
• Bowel perforation
  • Peritonitis
  • Septicemia

Differential Diagnosis

• Small bowel obstruction
• Large bowel obstruction
  • Volvulus, Neoplastic Disease, Paralytic ileus, Pseudo-obstruction
• Colitis
  • Infectious, Inflammatory, Ischemic

Evaluation

Toxic megacolon on KUB

CT with toxic megacolon showing submucosal edema and mucosal enhancement of the ascending and descending colon giving the appearance of the “target sign”.

CT showing is diffuse dilation of the colon with air and fluid levels present. There is diffuse wall thickening and enhancement in the rectosigmoid colon. The descending, transverse, and ascending colon are dilated to as much as 8.5cm. These features are consistent with a diagnosis of toxic megacolon.

• Plain abdominal radiographs:
  • Colonic Dilation ≥6 cm diameter
  • Loss of haustra, "thumb-printing" (bowel edema)
  • Air-fluid levels
• Abdominal Ultrasound:
  • Thin colonic walls with loss of haustra coli
  • Diameter ≥6cm with gaseous content
• Labs:
  • Leukocytosis
  • Electrolyte derangements: Hypokalemia, Hypomagnesemia
  • Elevated ESR/CRP
  • Anemia
  • Hypoalbuminemia

Management

• Fluid resuscitation
• IV corticosteroids
  • Hydrocortisone IV 100mg q6h
• Triple Antibiotic Therapy
  • Ampicillin 2 g IV q6h PLUS Metronidazole 500mg IV q6h PLUS Gentamicin 7mg/kg q24h or Ciprofloxacin 400mg IV q12h OR
  • Imipenem 500mg IV q6h
• Electrolyte repletion
  • Aggressively treat hypokalemia and hypomagnesemia because these can exacerbate dilation
• Emergent Surgical Consultation

• Obtain blood cultures, stool cultures, C. Diff Toxin
• If known cause is C. Diff treat with Vancomycin or Metronidazole
• If known cause is CMV can add Ganciclovir

• Avoid
  • Anticholinergics, anti-motility agents, opioids which can worsen dilation
  • Sulfasalazine or 5-aminosalicylate (5-ASA) unhelpful
  • Nasogastric (NG) Tube NOT effective in reducing colonic distention

Disposition

• Admit

See Also

• Crohn's disease
• Ulcerative Colitis