OBJECTIVE: To evaluate the prevalence and the clinical evolution of patients with an initial diagnosis of indeterminate colitis. DESIGN: Retrospective, observational study. SETTING: Fifteen gastrointestinal units in northern Italy. PARTICIPANTS: Patients with an initial diagnosis of indeterminate colitis seen between 1988 and 1993. INTERVENTIONS: Patients were traced through a common database and centres were requested to update their clinical follow-up. MAIN OUTCOME MEASURES: Frequency of patients with an initial diagnosis of indeterminate colitis among those with IBD; rate of patients who subsequently had a definite diagnosis of either Crohn's disease or ulcerative colitis. RESULTS: Fifty out of 1113 IBD patients (4.6%) had been diagnosed as having indeterminate colitis. During follow-up, 37 patients (72.5%) had a definite diagnosis of either Crohn's disease or ulcerative colitis. The cumulative probability of having a definite diagnosis of either ulcerative colitis or Crohn's disease was 80% 8 years after the first one (i.e. the first diagnosis). The probability of having a diagnosis of Crohn's disease was increased in patients with fever at onset, segmental endoscopic lesions or extra-intestinal complications and in current smokers. The probability of having a diagnosis of ulcerative colitis was increased in patients who had not undergone appendectomy before diagnosis. CONCLUSIONS: In our area, indeterminate colitis accounts for about 5% of initial diagnoses of IBD. In about 80% of patients, a diagnosis of either ulcerative colitis or Crohn's disease is made within 8 years. Several clinical and demographic features can help in identifying those patients more likely to have a subsequent diagnosis of Crohn's disease and those more likely to have a subsequent diagnosis of ulcerative colitis.
OBJECTIVE: To evaluate the prevalence and the clinical evolution of patients with an initial diagnosis of indeterminate colitis. DESIGN: Retrospective, observational study. SETTING: Fifteen gastrointestinal units in northern Italy. PARTICIPANTS: Patients with an initial diagnosis of indeterminate colitis seen between 1988 and 1993. INTERVENTIONS:Patients were traced through a common database and centres were requested to update their clinical follow-up. MAIN OUTCOME MEASURES: Frequency of patients with an initial diagnosis of indeterminate colitis among those with IBD; rate of patients who subsequently had a definite diagnosis of either Crohn's disease or ulcerative colitis. RESULTS: Fifty out of 1113 IBDpatients (4.6%) had been diagnosed as having indeterminate colitis. During follow-up, 37 patients (72.5%) had a definite diagnosis of either Crohn's disease or ulcerative colitis. The cumulative probability of having a definite diagnosis of either ulcerative colitis or Crohn's disease was 80% 8 years after the first one (i.e. the first diagnosis). The probability of having a diagnosis of Crohn's disease was increased in patients with fever at onset, segmental endoscopic lesions or extra-intestinal complications and in current smokers. The probability of having a diagnosis of ulcerative colitis was increased in patients who had not undergone appendectomy before diagnosis. CONCLUSIONS: In our area, indeterminate colitis accounts for about 5% of initial diagnoses of IBD. In about 80% of patients, a diagnosis of either ulcerative colitis or Crohn's disease is made within 8 years. Several clinical and demographic features can help in identifying those patients more likely to have a subsequent diagnosis of Crohn's disease and those more likely to have a subsequent diagnosis of ulcerative colitis.