History and exam

Key diagnostic factors

common

history of inflammatory bowel disease

Toxic megacolon has been reported to complicate ulcerative colitis with varying frequency ranging from 1.6% to 22%, though the lifetime incidence of toxic colitis and toxic megacolon (TC/TM) in patients with UC is less than 5%.[4][5] The reported incidence of toxic megacolon complicating Crohn colitis has great variability, ranging from 0% to 20% with a probable frequency of 2% to 4%.[4]

Discontinuation, or significant dosage decreases, of therapeutic medications including corticosteroids, sulfasalazine, or other aminosalicylates can trigger the development of toxic megacolon in patients with inflammatory bowel disease, presumably due to inadequate treatment of the underlying inflammatory bowel disease.[17]

history of exposure to infectious agents

Infectious agents including Clostridium difficile, Salmonella, Shigella, Campylobacter, Yersinia, Entamoeba histolytica, Cryptosporidium, and cytomegalovirus have been associated with colitis and toxic megacolon.[9][10][11][12][13][14][15][16]

history of recent antibiotic use

Pseudomembranous colitis often occurs as a complication of Clostridium difficile infections due to the use of broad-spectrum antibiotics, especially cephalosporins, clindamycin, and fluoroquinolones.[28] Toxic megacolon has a reported lifetime incidence of 0.4% to 3% in patients with pseudomembranous colitis.[6]

history of HIV/AIDS/immunosuppressed state

Toxic megacolon has been reported as a consequence of cytomegalovirus in patients with HIV or AIDS.[14][15][16]

fevers/chills

Frequently present in TC/TM.

tachycardia

Frequently present in TC/TM.

mental status changes

Frequently present in TC/TM.

hypotension

Frequently present in TC/TM.

abdominal distention

Toxic megacolon is characterized by either total or segmental colonic dilation >6 cm, which usually results in clinically evident abdominal distention though the degree of distention is variable.

Other diagnostic factors

common

diarrhea

Prior bouts of diarrhea, often lasting a week or longer, may be a presenting symptom if toxic megacolon is related to either ulcerative colitis (usually bloody diarrhea) or infectious colitis. In some cases, improvement of diarrhea heralds the onset of colonic dilation.

abdominal pain

Characterized as diffuse or focal crampy abdominal pain and may be relieved with bowel movements.

abdominal tenderness

The abdomen may be either focal or diffusely tender but the degree of pain may be masked by concurrent use of high-dose corticosteroid therapy. Localized and rebound tenderness may suggest impending perforation, while generalized peritonitis often indicates free perforation.

Risk factors

strong

ulcerative colitis (UC)

Although inflammatory bowel disease is the most common cause of toxic megacolon, the lifetime incidence in patients with UC is less than 5%.[4][5][8] In typical UC, inflammation and ulceration is limited to the mucosa; however, in toxic megacolon, inflammation extends into the smooth muscle layer, which may induce neural injury in the colonic wall, causing colonic paralysis and pronounced colonic dilation, thinning of the bowel wall, and deep ulcerations.[7][21][22]

In a study of patients requiring a colectomy for UC, a correlation between the depth of invasion and the degree of colonic dilation was demonstrated.[7][22] Toxic megacolon as a complication of an acute exacerbation of UC is an indication for urgent surgery.[5]

Crohn colitis

The reported incidence of toxic megacolon complicating Crohn colitis has great variability, ranging from 0% to 20% with a probable frequency of 2% to 4%.[4]

It has been suggested that toxic megacolon is more likely to occur early in the course of Crohn colitis and that the fibrosing and segmental nature of Crohn disease makes toxic megacolon less likely than with ulcerative colitis.

pseudomembranous colitis

Toxic megacolon has a reported lifetime incidence of 0.4% to 3% in patients with pseudomembranous colitis.[4] The incidence of toxic megacolon in patients with Clostridium difficile-associated colitis is increasing due to increasing prevalence of pseudomembranous colitis and other infectious colitides.[7]

Pathologic hallmarks include diffuse ulcerations, raised mucosal nodules, yellowish-white superficial plaques interspersed between normal segments of mucosa, and extensive denudation seen on endoscopic inspection. However, stool testing has become a safer way to diagnose C difficile colitis than endoscopic evaluation of the acutely diseased and inflamed colon.

infectious colitis

Infectious agents including Clostridium difficile, Salmonella, Shigella, Campylobacter, Yersinia, Entamoeba histolytica, Cryptosporidium, and cytomegalovirus have been associated with colitis and toxic megacolon.[9][10][11][12][13][14][15][16]

HIV/AIDS/immunosuppression

Toxic megacolon has been reported as a consequence of cytomegalovirus infection in patients with HIV or AIDS.[14][15][16]

discontinuation of medications for inflammatory bowel disease

Discontinuation, or significant dosage decreases, of therapeutic medications including corticosteroids, sulfasalazine, or other aminosalicylates can trigger the development of toxic megacolon in patients with inflammatory bowel disease.[17]

antimotility agents

Drugs including narcotics, antidiarrheals, and anticholinergics, as well as some antidepressants, have been recognized to exacerbate colonic dilation and should be discontinued immediately if toxic megacolon is present.[7][17]

weak

chemotherapy/chemical immunosuppression

Antineoplastic agents and other associated immunosuppressants have been associated with toxic megacolon.[18][19][20]

electrolyte abnormalities

Several studies have noted electrolyte abnormalities in toxic colitis/toxic megacolon, especially hypokalemia; however, whether this is a cause or an effect is debatable. Correction of electrolyte abnormalities, however, is a primary treatment objective.

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