1. Irritable Bowel Syndrome Rahul Gladwin, MS3 University of Health Sciences Antigua School of Medicine Email: rahul[AT]rahulgladwin.com

2. Definition & Stats  Characterized by irregular bowel habits and abdominal pain without any structural abnormalities.  Throughout the world, 10-20% of people might have IBS  More common in women  Compare with inflammatory bowel disease.

3. Associations  Symptoms usually overlap with other disorders such as fibromyalgia, backache, headache, and genitourinary symptoms.  Other affecting factors include altered gastrointestinal GI motility, visceral sensitivity, abnormal central processing, disturbance of brain-gut interaction, genetic and environmental factors, autonomic and hormonal events, and psychosocial disturbances.

4. Clinical  Usually affects individuals younger than 45.  Decreased incidence in older individuals  Women are 2-3 times more likely to have IBS. [80% patients are women]

5. Findings  The main finding is abdominal pain during morning hours – which may be in the hypogastrium (25%), right (20%), left (20%), and epigastrium (10%).  Other findings may include defecation straining, urgency or a feeling of incomplete bowel movement, bloating, and passing mucus.

6. DIAGNOSTIC CRITERIA (from Harrisons)

7. Pathophysiology  Poorly understood.  May be due to abnormal gut motor and sensory activity, central neural dysfunction, stress, and psychological disturbances.  Studies of motor and colonic myoelectrical activity under unstimulated conditions are normal.

8. Pathophysiology  There is increased rectosigmoid activity 3 h after eating.  Stimulation with rectal balloon (Flexi- Seal®) of diarrhea-prone patients showed distention-evoked contractile activity.  IBS patients show exaggerated sensory responses to visceral stimulation suggesting visceral afferent dysfunction..

9. Pathophysiology  Lipids exaggerate sensation of gas, discomfort, and pain in IBS patients.  There is a correlation between stress and emotional disorders and IBS.  IBS patients have increased activity in the mid-cingulate cortex – associated with visceral pain, response selection and attention process.  Study done in January 2011 shows that small intestine bacterial overgrowth (SIBO) may play a role in IBS.

10. Pathophysiology  Gastroenteritis may predispose IBS in 25% of patients - Campylobacter, Salmonella, and Shigella most likely involved.  IBS patients more likely to have increased serotonin (5HT)-containing enterochromaffin cells in the colon.  Serotonin plays an important role in visceral perception and regulation of GI motility

11. Differentials  Lactase deficiency.  Celiac sprue.  Side-effects from anticholinergic, antihypertensive, and antidepressant medications.  Biliary tract disease, intestinal ischemia, peptic ulcer disorders, and carcinoma of the stomach and pancreas.  Diverticular disease of the colon, inflammatory bowel disease  Giardia  Laxative abuse  Hyperthyroidism

12. Treatments

13.  High-fiber diets.  Anticholinergic drugs inhibit gastrocolic reflex (ipratropium bromide).  Anti-diarrheals (loperamide).  Anti-depressants – TCAs and SSRIs (fluoxetine).  Activated charcoal as part of anti-flatulence therapy.  Serotonin Receptor Agonist and Antagonists – alosetron, tegaserod.  Chloride Channel Activators – lubiprostone.

14. Sources  Harrisons Internal Medicine 17 th edition.  www.medpagetoday.com www.medpagetoday.com  www.ncbi.nlm.nih.gov www.ncbi.nlm.nih.gov