Drug-Induced Injury, Vascular, Congenital, and Miscellaneous Disorders

Jejunum and ileum are the longest parts in human gut and are the main locations where nutrition absorption occurs. The disease spectrum of jejunum and ileum is a bit different from that in duodenum and colon. Because of limited endoscopic accessibility and availability of tissue sample, many entities are less understood or recognized by pathologists. Besides Crohn’s disease, there are many nonneoplastic or congenital disorders in jejunum and ileum that can cause significant clinical issues and remain as diagnostic challenges for both clinicians and pathologists. In this chapter, we will focus on drug-induced injury, especially nonsteroidal anti-inflammatory drugs (NSAIDs)-induced enteropathy, ischemia or vasculitis, and congenital or other uncommon disorders that mainly involve jejunum and ileum.