Things to Know About Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is the commonest functional disorder of the gut. It affects up to 15% of the adult population at anyone time; however IBS is intermittent and it is likely that many more people experience it at some time in their lives. Affecting women about twice as often as men, IBS occurs at all ages, but most sufferers identified in population surveys have not consulted a doctor about it.

Presentation and diagnosis
The cluster of symptoms of IBS arise from a dysfunctional intestine no single symptom is unique to it and the entire cluster can occur in colitis, but differentiation from organic disease is usually easy. Abdominal pain may be mild and infrequent or severe enough to cause sweating and faintness and can occur in several places - anywhere between the nipples and the groins (front or back). Its features - relief on defecation (occasionally worsening) and a change in bowel habit at times when pain is experienced - often indicate that it originates in the colon. Usually stools become looser and/or more frequent but the reverse can occur, and the two bowel patterns may alternate.

Questions should concern the form or appearance of the stools as well as frequency of defecation, to avoid misdiagnosing constipation and diarrhea. Some patients have true constipation and/or diarrhea, perhaps alternating. The key questions are whether the stool is lumpy (pellety), implying slow intestinal transit, or liquid/runny, implying fast transit. A change to looser and more frequent stools may be missed if previous bowel habit is not inquired about because sometimes the change is welcomed as a spontaneous relief of constipation.

Some IBS patients have pseudo-constipation where the stools are normal in form but, after evacuation, the patient feels as if stool is still inside the rectum and continues to strain; this symptom is sometimes called rectal dissatisfaction. There may also be unproductive calls to stool or a constant awareness of the rectum, and the patient thinks he or she is constipated. Many patients have pseudo-diarrhea; their stools are not liquid but the calls to stool are frequent and urgent. In both pseudo constipation and pseudo-diarrhea, less common in men than in women, the symptoms result from an irritable rectum.

Abdominal bloating or distension (often varying within minutes) is very common, worsening as the day goes on and making the sufferer loosen or change their clothing. Some patients report passage of mucus with the stool.

Pathogenesis
The most consistent physiological abnormality is one of visceral sensation. All parts of the gut are abnormally sensitive to distension, which may translate into increased motor activity. Undue awareness of normal gut events may be due to upregulation of sensory receptors in the bowel wall, to augmented transmission of ascending sensory signals to the cerebral cortex, or to hypervigilance for visceral sensations.