Disorders of the small bowel

The small bowel comprises the duodenum, jejunum and ileum. The length can be 2-6 m in an adult; the ileum accounts for about 60%. It is suspended from the posterior abdominal wall by the mesentery, and derives its blood supply mainly from the superior mesenteric artery. The primary physiological function of the small bowel is the effective assimilation and digestion of food. This occurs as a result of a complex interplay of specialized anatomical features and functions, enzymatic action, neurohumoral responses, motility and various transport mechanisms. Diseases of the small bowel may be inflammatory, infective, neoplastic or vascular. This contribution focuses on coeliac disease, radiation enteritis, small-bowel neoplasms, Meckel's diverticulum, small-bowel ischaemia, short bowel syndrome and bacterial overgrowth.