Irritable bowel syndrome. Pathophysiological and clinical aspects

Abstract

Irritable bowel syndrome (IBS) is characterized by abdominal pain and/or discomfort related to abnormal bowel habits. Gastrointestinal (GI) motility disturbances, visceral hypersensitivity and psychological factors are involved in the pathophysiology of IBS. A number of unresolved issues regarding pathophysiology and the clinical presentation of IBS were studied.In IBS patients high-resolution manometry disclosed a higher proportion of duodenal individual pressure waves that propagated in a retrograde direction. This was especially pronounced postprandially. Combined high-resolution analysis and a detailed cluster analysis demonstrated abnormal findings in 22/26 (85%) patients compared with 10/26 (38%) with conventional manometric analysis. After duodenal lipid infusion, IBS patients increased their perceptual sensitivity in the sigmoid colon (barostat study) and showed an altered viscerosomatic referral pattern. This reaction was significantly more pronounced than in the controls.Abnormal levels of motilin in plasma and peptide YY (PYY) in the ascending colon were observed in IBS compared with the controls. IBS patients who presented predominantly with diarrhea, compared with those with constipation, exhibited lower plasma levels of motilin and higher levels of corticotropin releasing factor (CRF) and lower levels of neuropeptide Y (NPY) in colonic biopsies.A relationship between GI symptoms and food intake was reported by 63% of IBS patients. Female sex and anxiety predicted a high degree of subjective food intolerance.Quality of life (QOL) was reduced in IBS patients at referral centers compared with primary care. This difference was only obvious in females. Fatigue was related to other aspects of QOL, such as depression, anxiety, well-being and gastrointestinal symptom severity as well as gender.Conclusions: Food-related GI symptoms are common in IBS and may in part be explained by an exaggerated sensory component of the gastrocolonic response. IBS patients show an abnormal propagation pattern of individual duodenal pressure waves. Abnormal levels of motilin, CRF, PYY and NPY may be involved in the pathophysiology of IBS. IBS female patients seen at referral centers constitute a highly selected group with reduced QOL. Fatigue is a common symptom in IBS related to general well-being and psychological and subjective gastrointestinal symptoms.