The pathology of chronic inflammatory bowel disease

Abstract

The histologic assessment of an endoscopic biopsy or intestinal resection is a cornerstone of the evaluation of a child suspected to have inflammatory bowel disease (IBD). Endoscopic biopsies and surgical specimens are obtained most frequently in those cases which have a significant clinical course, in the setting of unidentified pathogen by routine cultures, to confirm the diagnosis of IBD, and in the course of treatment or to monitor response to therapy. Although IBD typically refers to two major entities, ulcerative colitis (UC) and Crohn disease (CD), the differential diagnosis of colitis and enteritis in pediatrics encompasses numerous disorders, including self-limited entities related to infections or medication, or enteritis due to immunodeficiency states. Because these entities may have overlapping histologic features, close collaboration between the pathologist and treating physician is important in arriving at a correct diagnosis and appropriate treatment plan. Furthermore, the current practice of endoscopy and biopsy has presented the pathologist with more extensive sampling of the gastrointestinal tract, with samples from earlier stages of disease, or from disease with atypical clinical features, emphasizing the importance of communication between gastroenterologist and pathologist. The purpose of this chapter is to discuss and illustrate the pathologic manifestations and differentiating features of UC and CD in biopsies and surgical specimens, the conditions that enter into the differential diagnosis as well as features that are atypical or which can result in difficulties in diagnosis.