Large Intestine: Toxic Megacolon

Definitions

• Toxic Megacolon
  • Potentially Lethal Complication of Colitis with Colonic Distention & Systemic Toxicity
• Toxic Colitis
  • Systemic Toxicity Due to Colitis without Evidence of Colonic Distention

Pathogenesis

• Not Fully Understood
• Mucosal Inflammation Releases Inflammatory Mediators
  • Increased Nitric Oxide (NO) Relaxes Smooth Muscle Causing Dilation
  • Damaged Muscular Layer Permits Translocation
• Mucosa Sloughs Losing Barrier Function & Becoming Septic

Causes

• Inflammatory Bowel Disease – Ulcerative Colitis More Common Than Crohn’s Disease
• Infectious Colitis
  • Clostridioides difficile
  • Salmonella
  • Shigella
  • Campylobacter
  • Yersinia
  • Entamoeba histolytica
  • Cryptosporidium
  • CMV Colitis – Most Common Cause in HIV/AIDS Patients
• Ischemic Colitis
• Kaposi Sarcoma
• Methotrexate Induced Pseudomembranous Colitis
• Steroid Discontinuation
• Narcotics
• Chemotherapy

Presentation

• Bloody Diarrhea
• Abdominal Pain
• Abdominal Distention
• Constipation or Obstipation
• Fever
• Altered Mental Status

Diagnosis

• Jalan’s Criteria
  • Radiographic Evidence of Colon Dilation > 6 cm
  • Plus ≥ 3 of:
    • Fever > 38 C
    • HR > 120 bpm
    • Neutrophilic Leukocytosis > 10,500
    • Anemia
  • Plus ≥ 1 of:
    • Dehydration
    • Altered Sensorium
    • Electrolyte Disturbances
    • Hypotension
• Abdominal XR & Clinical Presentation Usually Sufficient
  • Abdominal XR Can Monitor Progression
• CT May Identify Underlying Etiology
• Should Generally Avoid Endoscopy – High Risk for Perforation

Treatment

• Initial Tx: Bowel Rest (NPO & NGT), IV Fluids & Broad-Spectrum ABX
  • Serial Abdominal XR Every 12-24 Hours
  • If Due to IBD: Steroids (Infliximab if Steroid Resistant)
  • 50% Succeed & 50% Will Need Surgery
• Surgery Indications:
  • No Improvement After 48-72 Hours
  • Clinical Deterioration Despite Medical Tx
  • Abdominal Compartment Syndrome
  • Perforation
  • Peritonitis
  • Uncontrolled Hemorrhage
  • Uncontrolled Sepsis
• Surgical Options:
  • Preferred Procedure: Total Abdominal Colectomy or Subtotal Colectomy & End-Ileostomy
  • Turnbull Method (Blow-Hole Procedure)
    • Decompressive Transverse Loop Colostomy & Diverting Loop Ileostomy
    • Considered if Pregnant or Prohibitive Comorbidity without Abscess, Hemorrhage or Perforation