Objective:Inflammatory bowel diseases (IBDs) are idiopathic,chronic,and inflammatory intestinal disorders.The two main types,ulcerative colitis (UC) and Crohn’s disease (CD),sometimes mimic each other and are not readily distinguishable.The purpose of this study was to present a series of hospitalized cases,which could not initially be classified as a subtype of IBD,and to try to note roles of the terms indeterminate colitis (IC) and inflammatory bowel disease unclassified (IBDU) when such a dilemma arises.Methods:Medical records of 477 patients hospitalized due to IBD,during the period of January 2002 to April 2009,were retrospectively studied in the present paper.All available previous biopsies from endoscopies of these patients were reanalyzed.Results:Twenty-seven of 477 IBD patients (5.7%) had been initially diagnosed as having IBDU.Of them,23 received colonoscopy and histological examinations in our hospital.A total of 90% (9/10) and 66.7% (4/6) of patients,respectively,had a positive finding via wireless capsule endoscopy (CE) and double-balloon enteroscopy (DBE).The barium-swallow or small bowel follow-through (SBFT) was performed on 11 patients.Positive changes were observed under computer tomographic (CT) scanning in 89.5% (17/19) of patients.Reasonable treatment strategies were employed for all patients.Conclusions:Our data indicate that IBDU accounts for 5.7% of initial diagnoses of IBD.The definition of IBDU is valuable in clinical practice.For those who had no clear clinical,endoscopic,histological,or other features affording a diagnosis of either UC or CD,IBDU could be used parenthetically. Objective: Inflammatory bowel diseases (IBDs) are idiopathic, chronic, and inflammatory intestinal disorders. The two main types, ulcerative colitis (UC) and Crohn’s disease (CD), sometimes mimic each other and are not readily identifishable. The purpose of this study was to present a series of hospitalized cases, which could not initially be classified as a subtype of IBD, and try to note roles of the terms indeterminate colitis (IC) and inflammatory bowel disease unclassified (IBDU) when such a dilemma arises. Methods : Medical records of 477 patients hospitalized due to IBD, during the period of January 2002 to April 2009, were retrospectively studied in the present paper. Available previous biopsies from endoscopies of these patients were reanalyzed. Results: Twenty-seven of 477 IBD patients Had (5.7%) had been initially diagnosed as having IBDU. Of them, 23 received colonoscopy and histological examinations in our hospital. A total of 90% (9/10) and 66.7% (4/6) of patients, respectively, had a posi The barium-swallow or small bowel follow-through (SBFT) was performed on 11 patients. Positive changes were scanned under computer tomographic (CT) scanning in 89.5 % (17/19) of patients. Reasonable treatment strategies were employed for all patients. Conclusions: Our data indicate that IBDU accounts for 5.7% of initial diagnoses of IBD. The definition of IBDU is valuable in clinical practice. For those who had no clear clinical, endoscopic, histological, or other features affording a diagnosis of either UC or CD, IBDU could be used parenthetically.