Absence of submucosal edema and pseudopolyps on computed tomography in toxic megacolon is associated with increased mortality

Purpose: There is widespread use of computed tomography (CT) in abdominal pathologies, but few studies have examined CT features in toxic megacolon (TM). We aimed to describe common CT findings in TM, their prevalence across TM etiologies, and their impact on clinical outcomes. Methods: We performed a retrospective analysis (January 2014 – June 2024) of patients ≥ 18 years old with TM undergoing abdominopelvic contrast-enhanced CT. We independently reviewed CT images, and collected data on TM etiologies, demographics, clinical features, and treatment. The main outcomes were non-surgical resolution, colon perforation, and 30-day mortality. Results: We identified 70 patients with TM undergoing CT. Etiologies included Clostridioides difficile (C. diff) (38.6%), ischemic colitis (IsC) (28.6%), inflammatory bowel disease (IBD) (25.7%), and others (7.7%). The most common CT findings included loss of haustra (95.7%), colonic distention > 6 cm (94.3%), colonic wall thickening (85.7%), peri-colonic fat stranding (85.7%), submucosal edema (50%), colonic wall thinning (45.7%), ascites (42.9%), small bowel distention (20%), and pseudopolyps (12.9%). The median colonic diameter was 8.8 cm. Loss of haustra was less common in IsC (85% vs. 100% for IBD vs. 100% for C. diff, P = 0.045) while pseudopolyps were more common in IBD (33.3% vs. 3.7% for C. diff vs. 5% for IsC, P = 0.008). Pneumatosis coli was more common in IsC (20% vs. 5.6% for IBD vs. 0% for C. diff, P = 0.041). The 30-day mortality rate was 32.9% (N = 23). The absence of pseudopolyps (37.7% vs. 0%, P = 0.025) and submucosal edema (45.7% vs. 20%, P = 0.041) were associated with increased 30-day mortality. Conclusion: We identified several common CT findings in TM. IBD and C. diff were more commonly associated with sequelae of chronic inflammation. The absence of submucosal edema and pseudopolyps are associated with increased mortality in TM.