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Irritable Bowel Syndrome
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Irritable Bowel Syndrome

Irritable bowel syndrome
Irritable bowel syndrome is the most common of the functional bowel disorders, which are caused by disordered brain-gut interactions.
IBS is a chronic condition with periods of remissions and exacerbations; exacerbations can be due to stress.
Symptoms most often begin in late teens to early twenties; most patients are women.
PATHOPHYSIOLOGY
Etiologies are uncertain, but IBS may be due to: abnormal intestinal motility; hypersensitivity of the nerves in the gut in response to to colonic gas, bloating; intestinal inflammation.
Constipation or diarrhea may predominate, or may be "mixed" type.
Exacerbations may be triggered by stress, medications, foods, hormones.
SIGNS & SYMPTOMS
Patients experience constipation and diarrhea with abdominal pain.
Pain occurs an average of at least 1 day per week, associated with at least 2 of the following:
  • Defecation can improve or worsen abdominal pain
  • Change in defecation frequency
  • Change in stool appearance
Pain is also associated with bloating and abdominal distention; patients may also have other non-specific symptoms (headaches, fatigue, mood disorders, heart burn, etc.).
DIAGNOSIS
Rule out other etiologies; no specific objective exam or lab signs.
TREATMENTS
Lifestyle changes
  • Increase dietary fiber, supplement with psyllium, methylcellulose, wheat dextrin.
  • Avoid foods that produce excess gas (beans, cabbage, onions, etc).
    • Poorly absorbed, fermentable, monosaccharides, and short-chain carbohydrates - FOD-MAPs exacerbate bloating, flatulence, and diarrhea:
Fructose, lactose, fructans (ex: onions, garlic), wheat-based products, sorbitol (found in stone fruits), raffinose (found in legumes, Brussel sprouts, cabbage, lentils, soybeans).
  • Reduce stress.
Pharmacologic treatments
Medications are used in moderate to severe cases where lifestyle changes do not suffice.
  • Abdominal pain: Antispasmodics.
  • Constipation: lubiprostone, linaclotide, similar drug (increase fluid secretion and colonic transit).
  • Diarrhea: loperamide, bile sequestrants, serotonin 3 receptor antagonist (beware ischemic colitis).

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