Least predilection for distal ileum-

Carcinoid syndrome: Arise from the neuroendocrine organs and neuroendocrine differentiated gastrointestinal epithelium. More than 40% occur in small intestine( which includes ileum). Meckel's diveiculum is a congenital anomaly of GI tract, occurring in 2% population. It is commonly situated on the antimesentric border of the ileum, about 1 meter above the ileocaecal valve. It is an outpouching containing all the layers of intestinal wall in their normal orientation. Crohn's disease is an inflammatory bowel disease(IBD). Most common sites involved are terminal ileum, ileocaecal valve and caecum. Zollinger-Ellison-syndrome is characterised by multiple peptic ulcerations in the stomach, duodenum, and even jejunum, is caused by uncontrolled release of gastrin by a tumor and resulting in massive acid production. REF: TEXT BOOK OF ROBBINS BASIC PATHOLOGY NINTH EDITION PAGE.568,571,589. IMAGE REF: TEXTBOOK OF PATHOLOGY HARSHMOHAN, 6TH EDITION, FIG.20.20, PAGE: 562