Toxic megacolon is an acute form of colonic distension. It is characterized by a very dilated colon (megacolon), accompanied by abdominal distension (bloating), and sometimes fever, abdominal pain, or shock. Toxic megacolon is usually a complication of inflammatory bowel disease, such as ulcerative colitis and, more rarely, Crohns disease, and of some infections of the colon, including Clostridium difficile infections, which have led to pseudomembranous colitis. Other forms of megacolon exist and can be congenital (present since birth, such as Hirschsprungs disease). It can also be caused by Entamoeba histolytica and Shigella. It may also be caused by the use of loperamide. Signs and symptoms
Abdominal pain
Abdominal bloating
Abdominal tenderness
Fever
Tachycardia (rapid heart rate)
DehydrationThere may be signs of septic shock. A physical examination reveals abdominal tenderness and possible loss of bowel sounds. An abdominal radiography shows colonic dilation. White blood cell count is usually elevated. Severe sepsis may present with hypothermia or leukopenia. Complications
Perforation of the colon
Sepsis
ShockEmergency action may be required if severe abdominal pain develops, particularly if it is accompanied by fever, rapid heart rate, tenderness when the abdomen is pressed, bloody diarrhea, frequent diarrhea, or painful bowel movements. Colonoscopy is contraindicated, as it may rupture the dilated colon resulting in peritonitis and septic shock. Pathophysiology
The pathological process involves inflammation and damage to the colonic wall with unknown toxins breaking down the protective mucosal barrier and exposing the muscularis propria. There is relative destruction of the ganglion cells and swelling of the nerve fibers in the myenteric plexus, with concomitant damage to the colonic musculature.
8 (3): 195–201. doi:10.1111/j.1463-1318.2005.00887.x. PMID 16466559. S2CID 36384160. Toxic Megacolon at eMedicine


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