Toxic Megacolon is a severe complication of Inflammatory Bowel Disease and C diff Colitis, although it has been implicated in other infectious etiologies such as Infectious Colitis with Salmonella, Shigella, and Campylobacter, Amoebic dysentery (especially in the presence of loperamide), Hemolytic Uremic Syndrome, and disseminated CMV infection in those with HIV. Neural injury occurs as a result of inflammation extending from the lumen of the colon into the muscularis propria, resulting in altered motility and dilatation

Symptoms include abdominal pain, nausea, abdominal distention, fever, elevated lactate, hypotension and other signs of sepsis-like syndrome, anemia, and, as is typical of C. diff infection in general, marked leukocytosis. Colonic mucosa shows signs of edematous mucosa and raised, yellowish plaques or pseudomembranes. Diagnosis is suggested if colonic dilatation exceeds 6 cm.

Medical management includes vigorous intravenous hydration, oral vancomycin, IV metronidazole, bowel rest, bowel decompression, and attention to electrolytes. Vancomycin enemas can be included, but may have difficulty reaching the right side of the colon. Shifting of patient into prone position periodically may help pass flatus. Glucocorticoids are usually first line treatment for IBD related Toxic Megacolon. Endoscopic decompression is controversial, with some authors suggesting it may worsen disease and others improve it. Surgical intervention, including total colectomy, should be considered if no improvement in medical management in the first 48-72 hours, with clinically worsening or progressive dilatation of colon. Mortality is extremely high, with studies quoted between 27 and 80%.