Pathology of inflammatory bowel disease in children

The pathological diagnosis of inflammatory bowel disease in paediatric patients is challenging, both in the differentiation from other intestinal disorders and in the distinction of the two major disease entities, ulcerative colitis (UC) and Crohn's disease (CD). Mucosa with UC and CD shows evidence of chronic mucosal injury and variable activity. Most children with UC show a typical pattern of diffuse continuous colitis extending from the rectum and limited to the mucosa. However, a number of unusual variations (early presentation, effects of treatment, fulminant colitis, backwash ileitis, discontinuous caecal involvement and upper gastrointestinal tract inflammation) may potentially create confusion with CD. The patterns of involvement and histological appearance of mucosa with CD are more variable and subtle than UC, particularly early in the course of disease. The features most specific for CD are the presence of granulomas, extracolonic involvement, and involvement of deeper layers of the bowel wall.