Irritable bowel syndrome: diagnosis and pathogenesis

Abstract

Irritable bowel syndrome (IBS) is a common gastrointestinal (GI) disorder that considerably reduces the quality of life. It further represents an economic burden on society due to the high consumption of healthcare resources and the non-productivity of IBS patients. The diagnosis of IBS is based on symptom assessment and the Rome III criteria. A combination of the Rome III criteria, a physical examination, blood tests, gastroscopy and colonoscopy with biopsies is believed to be necessary for diagnosis. Duodenal chromogranin A cell density is a promising biomarker for the diagnosis of IBS. The pathogenesis of IBS seems to be multifactorial, with the following factors playing a central role in the pathogenesis of IBS: heritability and genetics, dietary/intestinal microbiota, low-grade inflammation, and disturbances in the neuroendocrine system (NES) of the gut. One hypothesis proposes that the cause of IBS is an altered NES, which would cause abnormal GI motility, secretions and sensation. All of these abnormalities are characteristic of IBS. Alterations in the NES could be the result of one or more of the following: genetic factors, dietary intake, intestinal flora, or low-grade inflammation. Post-infectious IBS (PI-IBS) and inflammatory bowel disease-associated IBS (IBD-IBS) represent a considerable subset of IBS cases. Patients with PI- and IBD-IBS exhibit low-grade mucosal inflammation, as well as abnormalities in the NES of the gut.

Keywords: Cholecystokinin; Chromogranin A; Diagnosis; Diet; Endocrine cells; Hereditary; Intestinal flora; Low-grade inflammation; Peptide YY; Serotonin.

Figure 1

The prevalence of irritable bowel syndrome according to Rome criteria in different countries. Reproduced from reference [1] with permission from Nova Science Publisher, Inc.

Figure 2

Chromogranin A cells in the duodenum. A: A healthy subject; B: A patient with irritable bowel syndrome (IBS); C: Controls and IBS patients. Reproduced from reference [1] with permission from Nova Science Publisher, Inc. ^bP < 0.01 vs control group.

Figure 3

Receiver-operator characteristic for chromogranin A cell density in the duodenum. Reproduced from reference [1] with permission from Nova Science Publisher, Inc. ROC: Receiver-operator characteristic.

Figure 4

Schematic drawing to illustrate the neuroendocrine system of the gut and the possible pathogenesis of irritable bowel syndrome. A: Schematic drawing of neuroendocrine system; B: Possible pathogenesis of irritable bowel syndrome. Reproduced from reference [1] with permission from Nova Science Publisher, Inc. NES: Neuroendocrine system.

Figure 5

Serotonin cells and polypeptide YY immunoreactive cells in the colon. A: A healthy control in serotonin cells; B: A patient with irritable bowel syndrome in serotonin cells; C: A healthy subject in polypeptide YY (PYY) immunoreactive cells; D: An irritable bowel syndrome patient in PYY immunoreactive cells. Reproduced from reference 1 with permission from Nova Science Publisher, Inc.