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Irritable Bowel Syndrome

Irritable Bowel Syndrome. Irritable Bowel Syndrome. A functional bowel disorder characterized by abdominal pain or discomfort and altered bowel habits in the absence of detectable structural abnormalities. . Pathophysiology of IBS. Poorly understood Proposed factors include:

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Irritable Bowel Syndrome

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  1. Irritable Bowel Syndrome

  2. Irritable Bowel Syndrome • A functional bowel disorder characterized by abdominal pain or discomfort and altered bowel habits in the absence of detectable structural abnormalities.

  3. Pathophysiology of IBS • Poorly understood • Proposed factors include: • Abnormal gut motor and sensory activity • Central neural dysfunction • Psychologic disturbances • Stress • Luminal factors

  4. Pathophysiology of IBS • Abnormal gut motor activity • Colonic motor abnormalites are more prominent under stimulated conditions • IBS patients may exhibit increased rectosigmoid motor activity for up to 3 hours after eating. • The motility index of high-amplitude propagating contractions in diarrhea-prone IBS patients were greatly increased compared to healthy subjects.

  5. Pathophysiology of IBS • Abnormal Gut Sensitivity • IBS patients frequently exhibit exaggerated sensory responses to visceral stimulation. • Postprandial pain has been temporally related to entry of the food bolus into the cecum of 74 % of patients. • IBS px’s have an increased area of referred pain. This is suggestive of postprandial symptoms occuring due to a nutrient-dependent exaggerated sensory component of the gastrocolonic response.

  6. Pathophysiology of IBS • Proposed mechanisms for gut hypersensitivity: • Increased end-organ sensitivity with recruitment of “silent” nociceptors • Spinal hyperxicitability with activation of nitric oxide and possibly other neurotransmitters • Endogenous modulation of caudadnociceptive transmission • Possible development of long term hyperalgesia due to development of neuroplasticity, resulting in permanent or semi permanent changes in neural response to visceral stimulation.

  7. Pathophysiology of IBS • CNS Factors • The association of emotional disorders and stress with IBS symptom exacerbation and therapeutic response to cerebral cortical therapy. • Mid-cingulategyrus shows greater activation on MRI in IBS patients • IBS patients show preferential activation on of the prefrontal lobe, which contains a vigilance network concerned with alertness

  8. Pathophysiology of IBS • PsychologicDisturbances • Abnormal psychiatric features are recorded in up to 80 % of IBS patients. • No single psychiatric diagnosis predominates. • Prior sexual and physical abuse has also shown a link with the development of IBS. • Psychological factors influence pain thresholds as stress alters sensory threshold.

  9. Pathophysiology of IBS • IBS and infection • 544 patient study with confirmed bactierial gastroenteritis • 1/4 of the patients had subsequent IBS • Microbes involved: Campylobacter, Salmonella, and Shigella • Patients w/ campylobacter infxn who are toxin positive are more like to develop IBS

  10. Pathophysiology of IBS • Serotonin and IBS • A link between the postprandial symptoms of IBS patients and serotonin • Serotonin containing enterochromaffin cells in the colon are increased in a subset of IBS-D patients. • Plasma 5-HT levels were significantly higher in this group then the control groups.

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