The anatomy and physiology of the ileal pouch and its relevance to pouch dysfunction

For the last 40 years, the ileal pouch-anal anastomosis has been used in patients with ulcerative colitis, familial adenomatous polyposis, and occasionally severe constipation to reconstruct the gastrointestinal tract after proctocolectomy. Although the procedure has generally been successful in helping patients avoid an ileostomy, it has come with its own set of problems. These include complications of the surgery such as fistulas and bowel obstruction, persistent inflammation of the pouch known as pouchitis, and functional problems related to the lack of expulsive peristalsis in the pouch. It is this last group of problems that is exacerbated by a poor diet, ill-advised anti-diarrheal medications, anal stenosis and pouch twists. As a consequence, patients with pouch problems are frequently referred for radiologic evaluation, with pouchography, defecation studies, and small bowel imaging commonly requested. In this review, the basic anatomy and physiology of the ileal pouch are discussed to provide a logical baseline against which to measure the anatomy of pouches and its relationship to the symptoms of pouch dysfunction.