[Indeterminate colitis (nonspecific inflammatory bowel disease)]

Distinguishing of indeterminate colitis from ulcerative colitis or Crohn's disease in more than 10% of IBD cases as separate diagnostic category (IIBD) is defined by: first, overlapping or paucity of features of two major IBD forms in acute fulminant colitides and few chronic slowly progressive cases without differentiating markers of chronicity, and second, inability to reach specific diagnosis during or after completed clinical, radiological, endoscopical and histopathological examination of chronic colitis with inconclusive presentation of IBD-compatible cases. It implicates the contemporary category of IIBD, until some new relevant data of further clinical (preferably natural history and course of the disease) and histopathological examination of prior biopsies will possibly reclassify 20-75% of these cases into ulcerative colitis category (up to 40%) or Crohn's disease (up to 25%) at a median of 10 years' follow-up. The presence of ileal and/or perianal disease as well as later evident granulomatous and/or fissuring disease, including cases with pouchitis and diversion colitis in addition, could be helpful in favouring of Crohn's disease. Lacking specific signs of disease, IIBD is not a distinct entity. Still, many patients remain in this category. The most far is acute fulminant disease in adolescents and young adults with unusual distribution of transmural inflammation with deep fissuring ulcerations, sometimes of "collar-stud" type and normal mucosa between them, often with relative rectal sparing. There is significant risk of relapse and complications, but mild clinical course and even spontaneous regression are also reported. Failure of ileal pouch-anal anastomosis surgery is about 20% more frequent then in ulcerative colitis with overall worse prognosis in life expectations. Diagnostic problems and the main presentations are discussed in detail, as well as genetic and etiopathogenetic basis for heterogeneity of IBD.