Irritable Bowel Syndrome

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. Treatments • 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 17th edition. • www.medpagetoday.com • www.ncbi.nlm.nih.gov