Background and Aim: Few studies have compared pancolitis and non-pancolitis E3 in adult patients with ulcerative colitis (UC). This study aimed to evaluate the natural disease courses and factors affecting outcomes between pancolitis and non-pancolitis E3. Methods: We retrospectively analyzed 117 patients, including 93 with extensive colitis (E3) and 24 with UC confined to the rectum or left-sided colon and appendiceal orifice inflammation at the time of diagnosis, who were regularly followed up for at least 1 year. Patients with E3 were divided into two groups according to the degree of disease extension: pancolitis group (disease extent up to the cecum or proximal ascending colon) and non-pancolitis E3 group (disease extent above the splenic flexure but not up to the proximal ascending colon). Clinical findings at diagnosis; comorbidity; medications; Mayo score; cumulative rates of corticosteroid, immunomodulator, and anti-tumor necrosis factor (anti-TNF) alpha use; relapse; and admission were compared between the pancolitis and non-pancolitis E3 groups. Results: The median follow-up duration of the 117 patients was 74 (range 15–158) months. Fifty-one patients (43.5%) had pancolitis. The Mayo score at initial diagnosis, cumulative relapse rate, and cumulative admission rate were significantly higher in the pancolitis group than in the non-pancolitis E3 group (P < 0.001, P = 0.023 and P = 0.007, respectively). However, there was no significant difference between the groups in the rates of cumulative immunomodulator and anti-TNF alpha use (P = 0.67 and P = 0.73, respectively). Conclusions: In patients with extensive UC (E3), pancolitis was associated with higher probabilities of cumulative relapse or admission, indicating poor prognosis.
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