ABSTRACT
Irritable bowel syndrome (IBS) is a complex, chronic disorder characterized by abdominal pain or discomfort and altered bowel habits. IBS is symptom dened and is thought to arise from a perturbance in the brain-gut axis. The diagnosis of IBS, which is classified as a functional gastrointestinal (GI) disorder, rests on fulllment of the Rome III criteria established by a multinational consensus group and is not associated with anatomical abnormalities. The diagnosis requires recurrent abdominal pain or discomfort of at least 6 months duration relieved by defecation and associated with changes in stool consistency or frequency (Table 13.1). Often patients are subgrouped into different categories based on their primary symptoms: constipation predominant (IBS-C), diarrhea predominant (IBS-D), or mixed. IBS-C is distinct from functional constipation, which is dened by its unique set of Rome III criteria. 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 or rectal bleeding. IBS is characterized by the absence of clinically measurable diagnostic tests. Therapy for IBS is thus directed toward addressing individual dietary patterns, food and nutrient intake, psychological factors, and comorbidities.
