Toxic Megacolon 

By usmlevideoss

Introduction

Toxic megacolon is a life-threatening complication of colonic inflammation characterized by acute colonic dilation (≥6 cm) accompanied by systemic toxicity. It is most commonly associated with inflammatory bowel diseases (IBD) such as ulcerative colitis or infectious colitis caused by Clostridioides difficile or other pathogens.

Etiology

Inflammatory causes:

  • Ulcerative colitis (most common).
  • Crohn’s disease.

Infectious causes:

  • Clostridioides difficile colitis.
  • Bacterial infections (Shigella, Salmonella, Campylobacter, E. coli).
  • Viral infections (cytomegalovirus).

Other causes:

  • Ischemic colitis.
  • Radiation colitis.
  • Colonic obstruction or pseudo-obstruction.

Epidemiology

  • Primarily affects individuals with IBD, especially ulcerative colitis.
  • Incidence is decreasing with improved disease management and timely treatment of infections like C. difficile.
  • Common in younger adults with IBD but can affect any age group with risk factors.

Pathophysiology

1.Colonic inflammation:

  • Severe inflammation leads to mucosal damage, cytokine release, and loss of mucosal integrity.

2.Toxicity and paralysis:

  • Inflammatory mediators and nitric oxide impair colonic smooth muscle function, leading to dilation and decreased motility.

3.Complications:

  • Distended colon is prone to ischemia, necrosis, and perforation, causing peritonitis and sepsis.

Clinical Manifestations

Systemic signs of toxicity:

  • Fever, tachycardia, hypotension.
  • Altered mental status.

Gastrointestinal symptoms:

  • Severe abdominal pain and distension.
  • Bloody diarrhea or ileus (decreased bowel movements).
  • Rectal bleeding in IBD-related cases.

Signs of perforation:

  • Rebound tenderness, guarding, or rigid abdomen.

Diagnosis

1.Clinical criteria:

  • Diagnosis requires radiographic evidence of colonic dilation (≥6 cm) plus at least 3 of the following:
  • Fever >38°C (100.4°F).
  • Heart rate >120 bpm.
  • WBC count >10,500/mcL.
  • Anemia.
  • And at least 1 of the following:
  • Hypotension.
  • Electrolyte disturbances.
  • Altered mental status.

2.Radiologic findings:

  • Plain abdominal X-ray: Colonic dilation ≥6 cm with loss of haustral pattern.
  • CT scan: Helps assess for perforation or abscess.

3.Laboratory tests:

  • Leukocytosis, anemia, electrolyte imbalances, and elevated inflammatory markers (CRP, ESR).
  • Stool studies: Rule out infections, especially C. difficile.

4.Endoscopy:

  • Avoided during acute episodes due to perforation risk but may help identify underlying causes once stabilized.

Treatment

1.Medical management:

  • Bowel rest: NPO (nothing by mouth) with IV fluids and electrolyte correction.
  • ceftriaxone with metronidazole).
  • Management of underlying cause:
  • IBD: IV corticosteroids (e.g., methylprednisolone).
  • C. difficile: Oral vancomycin or fidaxomicin, plus IV metronidazole in severe cases.

2.Monitoring:

  • Serial abdominal exams, vital signs, and imaging to assess response to treatment.

3.Surgical intervention:

  • Indicated for perforation, worsening clinical status, or failure of medical therapy within 48–72 hours.
  • Procedure: Subtotal colectomy with ileostomy.

Prognosis

  • Early recognition and treatment improve survival.
  • Mortality is 19-30% in severe cases, especially if perforation occurs.
  • Prompt medical or surgical intervention is critical for favorable outcomes.

SUPERPoint

Toxic megacolon is a life-threatening colonic dilation (≥6 cm) with systemic toxicity caused by severe inflammation, requiring immediate treatment with bowel rest, antibiotics, and corticosteroids. Surgery is indicated for complications or lack of improvement.

SUPERFormula

Patient presents with fever, tachycardia, leukocytosis, and hypotension + Acute colonic dilation (≥6 cm) + + underlying IBD or infection (C. difficile) + treated with bowel rest, antibiotics, and corticosteroids, or surgery in severe cases = Toxic megacolon.

Reference: 

McQuaid KR. Intestinal Motility Disorders. In: Papadakis MA, Rabow MW, McQuaid KR, Gandhi M. eds. Current Medical Diagnosis & Treatment 2025. McGraw-Hill Education; 2025

Feuerstein JD, Falchuk KR. Inflammatory Bowel Disease. In: McKean SC, Ross JJ, Dressler DD, Scheurer DB. eds. Principles and Practice of Hospital Medicine, 2e. McGraw-Hill Education; 2017