Pathology of chronic inflammatory bowel disease in children.

The term chronic inflammatory bowel disease is usually applied to the idiopathic varieties ulcerative colitis and Crohn's disease but actually encompasses a wide range of colonic inflammatory conditions, which in children includes indeterminate colitis, microscopic colitis, allergic colitis and Behçet's enterocolitis. The pathologist's opinion is considered the final arbiter in the diagnosis of inflammatory bowel disease but classification may be hampered by the considerable histological overlap between the various types of colitis. Accurate diagnosis, particularly in biopsy specimens, thus depends on clinical and radiological input as well as on appropriately selected and adequately prepared material. This chapter discusses in detail the morphological appearances of ulcerative colitis and Crohn's disease with particular emphasis on diagnosis by mucosal biopsy and differential diagnosis in the paediatric age group. The recent demonstration of ulceration-associated cell lineage and trefoil peptide expression in inflammatory bowel disease is also discussed.