Week 3: Irritable bowel syndrome

Question 1

Definition of IBS

Answer 1

• syndrome of symptoms including chronic abdominal pain and irregular bowel movements in the absence of structural abnormalities
• 3-12% prevalence in western countries

Question 2

Classifications of IBS

Answer 2

1. IBs with constipation
   - hard/lumpy stools greater than 25% of bowel movements (BM)
   - loose or water stools less than 25% of BMs
2. IBs with diarrhea
   - loose or watery stools greater than 25% of BW
   - hard stools less than 25% of BMs
3. Mixed IBs

Question 3

Pathophysiology of IBS

Answer 3

Complex functional disorder probably due to dysregulation of the brain-gut axis.

1. Psychological stress
   - sexual abuse as child
   - somatization present in a quarter of IBS patients
2. Physical
   - enterocolitis
   - hallmark: visceral hypersensitivity
   - gaseous distention-impaired transit of gas and decreased tolerance to intestinal gas
3. SIBO- small intestinal bacterial overgrowth
   - unconfirmed. response to antibiotics probably more related to colonic bacteria.

Question 4

Rome 3 Criteria for IBS diagnosis

Answer 4

recurrent abdominal pain for at least 3 days/month for past 3 months with 2 of the following:

• relief with defecation
• change in consistency of stools
• change in frequency of stools

Question 5

Red flags in GI assessment for IBS

Answer 5

• severe abdominal pain
• diarrhea
• weight loss
• rectal bleeding intertwined with stool
• fever
• abdominal or rectal mass
• Fe deficiency anemia, increased sed rate or CRP, low albumin, wbcs in stool, increased stool calprotectin

Question 6

Treatment of IBS

Answer 6

Difficult to treat.

1. Diet
   - decrease fat intake
   - decrease roughage- complex carbs and short chain carbs (non absorbed and gets fermented into gas)
   - avoiding FODMAP foods
   - fiber: psyllium
2. Exercise
3. psychotherapy
4. Drugs
   - anticholinergics, antidepressants, serotonin agonists and antagonists, antibiotics.

Question 7

Drugs for IBS

Answer 7

1. anticholinergics (anti-spamodics)
   - possibly inhibiting gesture colic reflex
   - hyoscyamine, atropine, scopolamine, phenobarbital
2. Anti-depressants
   - Tricyclics and SSRIs
3. HT agonists and antagonists
   - HT3R antagonist: alosetron, modest benefit in predom. diarrhea IBs
   - HT4R agonist: tegasorod, modest benefit for constipation predominant IBS (FDA removed this drug)
4. antibiotics
5. probiotics