Inflammatory bowel disease unclassified (IBDU) is referred to as colitis that has clinical characteristics related to inflammatory bowel disease, but cannot be clearly determined or classified as either ulcerative colitis (UC) or Crohn’s disease (CD) clinically. Over time, most patients with IBDU can be finally diagnosed as either UC or CD. Treatment of IBDU should follow a step-up strategy. This article describes the clinical characteristics, diagnosis and treatment of IBDU.

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