Irritable Bowel Syndrome

Functional Gastroesophageal Disorders

Defined as "variable combination of chronic/recurrent GI symptoms, not explained by structural/biochemical abnormalities"

3 main overlapping symptoms: (1) noncardiac chest pain, (2) functional dyspepsia, (3) irritable bowel syndrome

Esophageal–caused by reflux–globus sensation(back of throat), rumination(regurgitate), chest pain, heartburn, dysphagia

Gastroduodenal – functional (nonulcer) dyspepesia (gastroparesis, acid hypersecretion), aerophagia (belching)

Bowel – irritable bowel syndrome (see below), functional abdominal bloating, constipation, diarrhea

Biliary functional disorders – dysfunction of gall bladder or Sphincter of Oddi

Anorectal probs – functional incontinence, anorectal pain (levitor ani, proctalgia fugax) dyschezia

Irritable Bowel Syndrome (IBS) – costs $8 billion/year

Irritable bowel syndrome is a very common chronic condition with no increased risk of mortality

12% of all in primary care practice, 28% of GI practice, 9-23% of patients that see doctor worldwide
probably same incidence in men and women – gender discrepancies match doctor visit discrepancies

(1) greater than three months of recurrent abdominal pain or discomfort
(2) relief with defacation, change in stool consistency/frequency
(3) >2 of these on 25% of occasions: altered stool frequency/form/passage, passage of mucus, bloating/abd. distention

dysmenorrhea, frequent urination, dysparousia (pain during intercourse), noncardiac chest pain, migraine headaches
sexual abuse/rape/incest correlate with more severe IBS – IBS patients 2.8x more likely to have abuse
only 1/3 IBS patients see a doctor – those that do have higher incidence of hypochondriasis, depression, hysteria

Typical Symptoms – pain, bloating, sense that bowel not completely moved, weight gain, left lower quad tenderness

aggreviated by meals, alleviated by defacation, looser stools concurrent with pain onset

* Symptoms indicating it is NOT IBS: nocternal pain/diarrhea (especially if wake from sleep), blood in stool, weight loss, fever, progressive course, new symptoms, steatorrhea, dehydration, age greater than 45

Conditions that look Like IBS:

diarrhea: antacids with Mg⁺⁺, antibiotics, sorbitol (many lipid meds), theophilline, theopyroxin
constipation: antacids with Ca⁺⁺/Al⁺⁺, anticholinergics, Ca⁺⁺ channel blockers, opiate analgesics, phenothiazines

Initial Tests: for all: CBC – anemia, ESR – inflammation, chemistry panel – glucose levels

diarrhea: sigmoidoscopy with biopsy, examine stool for fecal leukocytes, ova, parasites, excessive fecal fat, thyroid test

More extensive tests: - constipation: colonic transit, anal manometry, defecography

diarrhea: stool osmolarity/electrolyte test, laxitive screen, small bowel/colonic transit, cholestyramine test
pain/bloating: small bowel, breath test (for bacteria), small bowel manometry

Pathophysiology of Irritable Bowel Syndrome – many hypotheses

Abnormal Motility – an early hypothesis

Luminal Factors – lactose, sorbitol and certain sugars, bile salts, short chain fatty acids, food allergens

Psychological Distress – even in normal patients, stress affects colonic contractility – IBS more so

IBS patients have higher abdominal pain and bowel dysfunction during periods of high stress
IBS strongly associated with depression, anxiety, and somatization

Myoelectric Marker – measure motility – IBS: higher sigmoidal motility after meal Þ spasm Þ painÞ diarrhea

Abnormal Sensation ("Visceral Hyperalgesia") – any sensation other than fullness after meal or need to defacate

IBS patients more sensitive to inflation of balloon in jejunum or sigmoidal colon

Brain/gut interaction – current theory to explain all functional bowel disease

synapses that turn off pain pathway no longer active after painful event (infection, chemical exposure, rape, trauma)

enteric neurons – silent nocireceptors turned on and stay on – chronic pain
spinal cord – afferent to dorsal horn sensitized
brain – PET scan: physiological difference in response to pain (rectal distention) in IBS vs. non-IBS patients

potential mediators: cytokines, eicosanoids, growth factors, neuropeptides, histamines, glutamine

corticotropin releasing factor (CRF) – release stimulated by psychological stress, IL-18, IL-1, noxious stimuli
shown to cause increased colonic contractility and viceral hyperalgesia in IBS patients
increases anorexia, catacholamines, hypertension, hyperglycemia, vagal activty/decrease gastric emptying

Treatment – drive back to normal state

Dietary modification – low fat/high fiber – controversial (most studies poorly designed) but 2/3 get better with 5 yrs. of fiber
Cognitive-behavioral therapy (diaries/exercises-change thoughts/behavior), psychotherapy, hypnosis, relaxation therapy
Drugs: IBS diarrhea anti-diarrheal agents for IBS diarrhea, prokinetic agents for IBS constipation

pain/gas/bloating: antispasmodics (such as peppermint oil) and opiods
chronic pain syndromes – antidepressents (esp. tricyclics, due to blockade of spinal NMDA receptor)