Persistent non-toxic megacolon in ulcerative colitis: a case report of broad disruption and scar replacement of the muscularis propria.

Ulcerative colitis-associated colonic dilatation is clinically important because it may progress to perforation or toxic megacolon. However, surgical decision-making is difficult when systemic toxicity is absent. An 83-year-old woman with long-standing pancolitis-type ulcerative colitis was admitted with worsening bloody diarrhea and abdominal pain. Despite high-dose corticosteroids and infliximab, computed tomography revealed marked colonic dilatation predominantly involving the transverse colon. Although she had anemia, she did not meet the Jalan criteria for toxic megacolon because she lacked high fever, marked tachycardia, leukocytosis, and additional signs of systemic deterioration. Serial abdominal radiographs showed progressive dilatation from approximately 70 mm to 95 mm despite intensive medical therapy. Surgery was selected after multidisciplinary reassessment. Histopathological examination revealed deep ulceration with erosion, broad disruption of the muscularis propria, and scar replacement in the dilated segment, indicating severe structural bowel-wall injury. No major postoperative complications occurred, although rehabilitation transfer was required because of decreased activities of daily living. This case suggests that persistent or progressive colonic dilatation in ulcerative colitis, even without systemic toxicity, may reflect advanced mural injury and should prompt repeated surgical assessment based on serial radiological findings.