Irritable Bowel Syndrome
Irritable bowel syndrome (IBS) is a complex, chronic disorder characterized by abdominal pain or discomfort and altered bowel habits. IBS is symptom dened, not associated with gross  anatomic abnormality, and is thought to arise from a perturbance in the brain-gut axis. The diagnosis of IBS rests on fulllment of the Rome III clinical criteria established by a multinational consensus group. The diagnosis requires the following: recurrent abdominal pain or discomfort of at least six months’ duration relieved by defecation and associated with changes in stool consistency or frequency (Table 14.1). Patients are subgrouped into different categories based on their primary symptoms: constipation predominant (IBS-C), diarrhea predominant (IBS-D), or mixed (IBS-M). The diagnosis of IBS is further supported by the age of symptom onset, which typically is prior to the fth decade of life, the lack of nocturnal symptoms, and the absence of weight loss, anemia, or rectal bleeding. The diagnosis of IBS is characterized by the absence of clinically measurable diagnostic tests.