Clinical characteristics of patients with difficult-to-treat ulcerative colitis: a nested case-control study using a Japanese claims database. - Matsuoka, Katsuyoshi; Igarashi, Ataru; Sato, Noriko; Mizuno, Naomi; Ishii, Manabu; Iizuka, Masato; Iwasaki, Katsuhiko; Shoji, Ayako; Hisamatsu, Tadakazu (Intestinal Research, 2026)