Indeterminate colitis in clinical practice

Abstract

A precise diagnosis of colitis is important for medical and surgical therapy. ‘Indeterminate colitis’ (IC) was originally proposed as a substitute for ‘unclassified colitis’ for patients in whom examination of the surgical specimens showed overlap of pathological features of ulcerative colitis (UC) and Crohn's disease (CD). Nowadays, the term is applied more widely and includes all cases with endoscopic, radiographic and histological evidence of chronic idiopathic inflammatory bowel disease confined to the colon, but without fulfilment of diagnostic criteria for UC or CD. Some authors also include patients for whom the diagnosis changes over time. More than 5% of all patients with idiopathic inflammatory bowel disease are labelled as IC patients. The diagnosis relies upon macroscopy and microscopy. Macroscopic examination is performed by the endoscopist, and the pathologist is responsible for mucosal biopsy samples, so the diagnosis implies clinico-pathological collaboration. In comparison with the original description, microscopic features of the deeper layers of the bowel wall cannot be used in diagnosis when only mucosal biopsies are available. It is generally accepted that IC is a ‘temporary diagnosis’. With time, 50–80% of patients can be reclassified as definite UC or CD, although a minority of cases remain indeterminate for a longer period. These patients are often antineutrophil cytoplasmic antibody and anti Saccharomyces cerevisiae antibody negative. Therefore, some authors have suggested that IC might be a separate entity.