Last updated: March 21, 2023

Summarytoggle arrow icon

Megacolon is the dilation of the colon in the absence of a mechanical obstruction (e.g., colonic tumor/stricture). There are three etiological types of megacolon: acute, chronic, and toxic megacolon. Acute megacolon (Ogilvie's syndrome) is the acute dilation of the colon, characteristically seen in severely medically/surgically ill patients, probably secondary to an electrolyte/metabolic imbalance. Chronic megacolon is the permanent dilation of the colon caused by chronic colonic dysmotility due to an underlying neuropathic (Hirschsprung's disease, chronic Chagas disease) or myopathic (Duchenne's muscular dystrophy) disorder. Patients with acute/chronic megacolon typically present with abdominal pain, bloating, and constipation. Toxic megacolon is a life-threatening dilation of the colon associated with systemic toxicity due to infectious colitis (C. difficile pseudomembranous colitis, Salmonella enterocolitis) or inflammatory colitis (inflammatory bowel disease). Patients typically present with signs of sepsis (tachycardia, hypotension) and a history of abdominal pain and bloody diarrhea. Abdominal x-rays demonstrate a colonic dilation, with/without air-fluid levels, and preserved haustrae. Contrast-enhanced CT scans can identify/rule out a mechanical colonic obstruction and possible complications (colonic ischemia/perforation). Patients with acute/chronic megacolon can often be treated conservatively with bowel rest, dietary modifications, prokinetic drugs, and/or neostigmine. Colonoscopic decompression is often successful in patients with acute megacolon. Surgical intervention for acute/chronic megacolon (colectomy and ileorectal anastomosis) is indicated if conservative treatment fails. Conservative management of toxic megacolon includes bowel rest, IV antibiotics (for infectious colitis), IV steroids (for inflammatory bowel disease). There is a high risk of colonic perforation in patients with toxic megacolon. Hence, no improvement to medical therapy within 24–72 hours is an indication to perform surgery (subtotal colectomy and end ileostomy).

Classificationtoggle arrow icon

Acute megacolon (Acute colonic pseudo-obstruction or Ogilvie's syndrome)toggle arrow icon

Chronic megacolon (chronic colonic pseudo-obstruction)toggle arrow icon

Toxic megacolontoggle arrow icon

Colonoscopy should be avoided in patients with suspected toxic megacolon since it increases the risk of colonic perforation.


Referencestoggle arrow icon

  1. Bharucha AE, Phillips SF. Megacolon: Acute, toxic, and chronic. Curr Treat Options Gastro. 1999; 2 (6): p.517–523.doi: 10.1007/s11938-999-0055-9 . | Open in Read by QxMD
  2. O'dwyer RH, Acosta A, Camilleri M, Burton D, Busciglio I, Bharucha AE. Clinical Features and Colonic Motor Disturbances in Chronic Megacolon in Adults. Dig Dis Sci. 2015; 60 (8): p.2398-2407.doi: 10.1007/s10620-015-3645-5 . | Open in Read by QxMD
  3. Camilleri M. Disorders of gastrointestinal motility in neurologic diseases. Mayo Clin Proc. 1990; 65 (6): p.825-846.
  4. Matsuda NM, Miller SM, Evora PR. The chronic gastrointestinal manifestations of Chagas disease. Clinics. 2009; 64 (12): p.1219-1224.doi: 10.1590/S1807-59322009001200013 . | Open in Read by QxMD
  5. Gladman MA, Knowles CH. Novel concepts in the diagnosis, pathophysiology and management of idiopathic megabowel. Colorectal Dis. 2008; 10 (6): p.531-538.doi: 10.1111/j.1463-1318.2007.01457.x . | Open in Read by QxMD
  6. Beattie GC, Peters RT, Guy S, Mendelson RM. Computed tomography in the assessment of suspected large bowel obstruction. ANZ J Surg. 2007; 77 (3): p.160-165.doi: 10.1111/j.1445-2197.2006.03998.x . | Open in Read by QxMD
  7. Kim ER, Rhee PL. How to interpret a functional or motility test - colon transit study. J Neurogastroenterol Motil. 2012; 18 (1): p.94-99.doi: 10.5056/jnm.2012.18.1.94 . | Open in Read by QxMD
  8. Gastrointestinal Motility, Part 2: Small-Bowel and Colon Transit. Updated: July 9, 2015. Accessed: January 29, 2017.
  9. Ranjan P, Bansal N, Sachdeva M, Jain P, Arora A. Colonic Transit Time: Current Methodology and its Clinical Implications. JIMSA. 2012; 25 (1): p.35.
  10. Farmer AD, Scott SM, Hobson AR. Gastrointestinal motility revisited: The wireless motility capsule. United European Gastroenterology Journal. 2013; 1 (6): p.413-421.doi: 10.1177/2050640613510161 . | Open in Read by QxMD
  11. Hanauer SB, Wald A. Acute and chronic megacolon. Curr Treat Options Gastroenterol. 2007; 10 (3): p.237-247.
  12. Vanek VW, Al-salti M. Acute pseudo-obstruction of the colon (Ogilvie's syndrome): An analysis of 400 cases. Dis Colon Rectum. 1986; 29 (3): p.203-210.
  13. Maloney N, Vargas HD. Acute intestinal pseudo-obstruction (Ogilvie's syndrome). Clin Colon Rectal Surg. 2005; 18 (2): p.96-101.doi: 10.1055/s-2005-870890 . | Open in Read by QxMD
  14. Jain A, Vargas HD. Advances and challenges in the management of acute colonic pseudo-obstruction (ogilvie syndrome). Clin Colon Rectal Surg. 2012; 25 (1): p.37-45.doi: 10.1055/s-0032-1301758 . | Open in Read by QxMD
  15. Geller A, Petersen BT, Gostout CJ. Endoscopic decompression for acute colonic pseudo-obstruction. Gastrointest Endosc. 1996; 44 (2): p.144-150.
  16. Mourelle M, Casellas F, Guarner F et al. Induction of nitric oxide synthase in colonic smooth muscle from patients with toxic megacolon. Gastroenterology. 1995; 109 (5): p.1497–1502.doi: 10.1016/0016-5085(95)90636-3 . | Open in Read by QxMD
  17. Ulcerative colitis in adults. Updated: May 13, 2019. Accessed: July 16, 2019.
  18. Toxic megacolon Treatment & Management. Updated: March 1, 2018. Accessed: July 16, 2019.
  19. Sheth SG, Lamont JT. Toxic megacolon. Lancet. 1998; 351 (9101): p.509-513.doi: 10.1016/S0140-6736(97)10475-5 . | Open in Read by QxMD
  20. Ausch C, Madoff RD, Gnant M, et al. Aetiology and surgical management of toxic megacolon. Colorectal Dis. 2005; 8 (3): p.195-201.doi: 10.1111/j.1463-1318.2005.00887.x . | Open in Read by QxMD
  21. Gan SI, Beck PL. A new look at toxic megacolon: an update and review of incidence, etiology, pathogenesis, and management. Am J Gastroenterol. 2003; 98 (11): p.2363-2371.doi: 10.1111/j.1572-0241.2003.07696.x . | Open in Read by QxMD

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