gastrointestinal disorders
Irritable Bowel Syndrome (IBS)
Etiology of IBS
Irritable bowel syndrome (IBS—previously called functional gastrointestinal [GI] disorders) is a disorder of gut-brain interaction. No anatomic cause can be found on laboratory tests, imaging studies, and biopsies. Emotional factors, diet, drugs, or hormones may precipitate or aggravate GI symptoms. Historically, the disorder was often considered as purely psychosomatic. Although psychosocial factors can be involved, IBS is better understood as a combination of physiologic and psychosocial factors. A variety of physiologic factors seem to be involved in IBS symptoms. These factors include Increased intestinal sensitivity (visceral hyperalgesia) Altered intestinal motility refers to hypersensitivity to normal amounts of intraluminal distention and heightened perception of pain in the presence of normal quantities of intestinal gas; it may result from remodeling of neural pathways in the gut-brain axis. Some patients (perhaps 1 in 7) have reported their IBS symptoms began after an episode of Overview of Gastroenteritis (termed postinfectious IBS). However, many patients have no demonstrable physiologic abnormalities, and, even in those who do, the abnormalities may not correlate with symptoms. Constipation may be explained by slower colonic transit, and Postprandial abdominal discomfort may be attributed to an exaggerated gastro-colonic reflex (the colonic contractile response to a meal), the presence of colonic high amplitude-propagated contractions, visceral hyperalgesia, or a combination of these factors. Fat ingestion may increase intestinal permeability and exaggerate hypersensitivity. Ingestion of food high in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (collectively called FODMAPs) are poorly absorbed in the small intestine and may increase colonic motility and secretion. Hormonal fluctuations affect bowel functions in women. Rectal sensitivity is increased during menses but not during other phases of the menstrual cycle. The effects of sex hormones on gastrointestinal transit are subtle. Psychologic distress is common among patients with IBS, especially in those who seek medical care. Some patients have Overview of Anxiety Disorders , 