Irritable Bowel Syndrome
Rahul Gladwin, MS3
University of Health Sciences Antigua
School of Medicine
Email: rahul[AT]rahulgladwin.com
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.
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.
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]
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.
DIAGNOSTIC CRITERIA (from
Harrisons)
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.
Pathophysiology
 There is increased rectosigmoid activity 3 h
after eating.
 Stimulation with rectal balloon (FlexiSeal®) of diarrhea-prone patients showed
distention-evoked contractile activity.
 IBS patients show exaggerated sensory
responses to visceral stimulation
suggesting visceral afferent dysfunction..
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.
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
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
Treatments
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.
Sources
 Harrisons Internal Medicine 17th
edition.
 www.medpagetoday.com
 www.ncbi.nlm.nih.gov