Written and peer-reviewed by physicians—but use at your own risk. Read our disclaimer.

banner image


Trusted medical answers—in seconds.

Get access to 1,000+ medical articles with instant search
and clinical tools.

Try free for 5 days


Last updated: February 5, 2021

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 48–72 hours is an indication to perform surgery (subtotal colectomy and end ileostomy).


References:[1][8][9][10][11][12][13][14][15][16][17][18][19][20] [21]

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

  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. Camilleri M. Disorders of gastrointestinal motility in neurologic diseases. Mayo Clin Proc. 1990; 65 (6): p.825-846.
  3. 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
  4. 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
  5. Cagir B. Intestinal Pseudo-Obstruction. In: Geibel J, Intestinal Pseudo-Obstruction. New York, NY: WebMD. http://emedicine.medscape.com/article/2162306. Updated: January 5, 2016. Accessed: January 29, 2017.
  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. http://jnm.snmjournals.org/content/56/9/1395.full. 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. Wesson DE. Congenital aganglionic megacolon (Hirschsprung disease). In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/congenital-aganglionic-megacolon-hirschsprung-disease.Last updated: November 9, 2016. Accessed: December 22, 2016.
  11. Camilleri M. Chronic intestinal pseudo-obstruction. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/chronic-intestinal-pseudo-obstruction.Last updated: July 18, 2016. Accessed: January 29, 2017.
  12. Manuel D. Chronic Megacolon. In: BS Anand, Chronic Megacolon. New York, NY: WebMD. http://emedicine.medscape.com/article/180955. Updated: March 28, 2016. Accessed: January 29, 2017.
  13. 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
  14. Hanauer SB, Wald A. Acute and chronic megacolon. Curr Treat Options Gastroenterol. 2007; 10 (3): p.237-247.
  15. 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
  16. Geller A, Petersen BT, Gostout CJ. Endoscopic decompression for acute colonic pseudo-obstruction. Gastrointest Endosc. 1996; 44 (2): p.144-150.
  17. Camilleri M. Acute colonic pseudo-obstruction (Ogilvie's syndrome). In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/acute-colonic-pseudo-obstruction-ogilvies-syndrome.Last updated: March 26, 2015. Accessed: January 29, 2017.
  18. Gamarra RM. Acute Megacolon. In: BS Anand, Acute Megacolon. New York, NY: WebMD. http://emedicine.medscape.com/article/180872. Updated: October 31, 2016. Accessed: January 29, 2017.
  19. 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.
  20. 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
  21. 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
  22. 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
  23. Ulcerative colitis in adults. http://www.dynamed.com/topics/dmp~AN~T114507#Colonic-complications. Updated: May 13, 2019. Accessed: July 16, 2019.
  24. Toxic megacolon Treatment & Management. https://emedicine.medscape.com/article/181054-treatment. Updated: March 1, 2018. Accessed: July 16, 2019.
  25. Lin B. Toxic Megacolon. In: Cagir B, Toxic Megacolon. New York, NY: WebMD. http://emedicine.medscape.com/article/181054. Updated: November 20, 2016. Accessed: January 10, 2017.
  26. Sheth SG, Lamont JT. Toxic megacolon. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/toxic-megacolon.Last updated: October 15, 2015. Accessed: January 30, 2017.
  27. 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
  28. 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
  29. 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