Clinical features and pattern of indeterminate colitis: Crohn's disease with ulcerative colitis-like clinical presentation

Background. Although an accurate diagnosis of inflammatory bowel disease (IBD) and differentiation between ulcerative colitis (UC) and Crohn's disease (CD) can be made in most patients, it is sometimes impossible to distinguish UC from CD even after thorough pathological study. Recently, clinicians have used the term indeterminate colitis (IC) for patients with features of both diseases that overlap temporarily or persistently. The frequency, reasons, and outcome of patients with a clinical diagnosis of IC based on radiological, endoscopic, and histopathological findings were investigated retrospectively. Methods. Based on records of 735 patients with IBD, IC was defined as having features of both UC and CD, with differentiation from each other impossible at least once during the observation period (average 6.8 years) based on diagnostic criteria using endoscopic, radiological, and histological findings. Results. Twenty-three patients were identified as having IC. They were classified into three patterns according to the clinical cource and the final diagnosis: (1) UC changing to CD (n = 8); (2) CD changing to UC (n = 5); and (3) UC or CD (n = 10). The frequency of IC was 24.5%–43.4% of colitis-type CD (n = 53), 2.3%–6.5% of all CD (n = 352), and 3.1% of IBD (n = 735). The reasons for the indetermination were temporary (56.5%) or persistent (43.5%) overlapping of UC-like and CD-like presentations. Treatment of IC was inappropriate in only two patients, and the prognoses of all patients except one were fairly good. Conclusions. Overlapping of UC-like presentations (persistent bloody stool and diffuse colitis) was frequently observed with Crohn's colitis but less so in CD patients during their clinical course. The basis of differentiation and treatment of IC needs more attention.