irritable bowel syndrome (IBS)

Introduction

A functional intestinal disorder associated with pain, alterations in pattern of defecation &/or bloat & distention.

Classification

• IBS with constipation (IBS-C)
  • hard or lumpy stools > 25%
  • loose or watery stools < 25%
• IBS with diarrhea (IBS-D)
  • hard or lumpy stools < 25%
  • loose or watery stools > 25%
• mixed IBS (IBS-M)
  • hard or lumpy stools > 25%
  • loose or watery stools > 25%
• unsubtyped IBS (IBS-U)
  • stool consistency does not meet criteria for IBS-C, IBS-D or IBS-M

Etiology

• inconclusive relationship with psychiatric disorders
  • depression, anxiety, psychosocial stress
  • somatoform disorders
  • post-traumatic stress disorder
• patients with psychiatric disorders are more likely to seek medical attention
• antibiotics (single course) may predispose to IBS
• indigested carbohydrates
  • fructose malabsorption (40%)
  • fructose & fructans can ellicit symptoms
• gluten sensitivity may play a role in some patients
• other disease associations
  • functional dyspepsia
  • GERD
  • cyclic vomiting syndrome
  • gastroparesis
  • fibromyalgia
  • headache
  • chronic pelvic pain
  • interstitial cystitis
  • dysmenorrhea
  • sexual dysfunction

Epidemiology

• prevalence is 15-20% in Western countries
  • prevalence is 7-16% in U.S.
• most individuals do not seek medical help
• 75% of patients in Western nations who seek medical help are female
• 25-50% of all outpatient referrals to gastroenterology
• commonly affects women age 20-40 years

Pathology

• dysfunction small intestinal smooth muscle response to:
  • stress, meals, peptides
• pain occurs secondary to intestinal hypermotility
• reduced sensory threshold for intestinal & rectal distention
• postulated mechanisms:
  • abnormal gastrointestinal motility
  • visceral afferent hypersensitivity with central sensitization
  • altered activation of the mucosal immune system
  • cytolethal distending toxin B from Campylobacter jejuni may play a role
    • cytolethal distending toxin B antibody may cross- react with host epithelial vinculin

Clinical manifestations

• usually begins in young adulthood
• continuous or recurrent symptoms for at least 3 months
  • abdominal pain or discomfort relieved by defecation or passing gas
  • alternating diarrhea & constipation
    • altered stool frequency
    • altered stool consistency - hard, loose, watery
    • altered stool passage
      • straining or urgency
      • feeling of incomplete evacuation
  • passage of mucus
  • bloat or abdominal distention
  • symptoms do NOT awaken the patient from sleep
• physical examination is generally normal
  • umbilical or epigastric tenderness may accompany small bowel involvement
  • tenderness over area of spastic colon may occur
• patients frequently have a history of multiple problems, especially allergies, headaches, arthralgias, kidney disease, dysparunia
• indications 'red flags' of a more serious disorder:
  • weight loss
  • bloody stools
  • nocturnal symptoms (bowel movements)
  • recent antibiotic use
  • symptom onset > 50 years of age
  • fever

Diagnostic criteria

• see Rome criteria
• reucrrent abdominal pain at least 1 day/week for 3 months
  • 2 of the following
    • defecation-related pain
    • change in stool frequency
    • change in stool consistency
• most patients with typical IBS symptoms without bleeding, weight loss or family history of colon cancer, inflammatory bowel disease or celiac sprue, do not need further diagnostic testing
• IBS patients with diarrhea or a mixture of diarrhea & constipation should be screened with blood tests for celiac disease
• when patients with IBS & diarrhea undergo colonoscopy, biopsy to rule out microscopic colitis

* rule out celiac disease prior to diagnosis of irritable bowel syndrome

Laboratory

• routine laboratory testing not indicated in the absence of 'red flags'
• complete blood count (CBC): generally within normal limits
• erythrocyte sedimentation rate (ESR): generally within normal limits
• stool specimen:
  • only fecal occult blood testing indicated for patients who meet Rome criteria
  • giardia antigen in stool
    • leukocytes, blood, culture, ova & parasites if travel history
  • bile acids in stool (optional)
  • Sudan black stain for fecal fat - negative findings
• urinalysis to exclude urinary cause of symptoms
• chemistry panel
  • serum TSH if diarrhea
• testing for celiac disease* if diarrhea
  • tissue transglutaminase IgA in serum
  • tissue transglutaminase IgG in serum if IgA deficient
  • test for celiac disease even if intermittent constipation
• lactose H2 breath test for suspected lactose intolerance
• screen for inflammatory bowel disease
  • fecal calprotectin (threshold 50 ug/g)
  • fecal lactoferrin (threshold 4-7 ug/g) to
  • C-reactive protein in serum only if above 2 tests unavailable
• low levels of food-specific serum IgE, esp wheat IgE Ab in serum & soy IgE Ab in serum
• investigational
  • cytolethal distending toxin B antibody
  • cytolethal distending toxin B gene (Loinc: 53943-7)
  • vinculin antibody

* rule out celiac disease prior to diagnosis of irritable bowel syndrome

Diagnostic procedures

• flexible sigmoidoscopy with colonic biopsy
  • indications
    • suspicion of inflammatory bowel disease
    • red flags or alarm features (see clinical manifestations)
    • patients who do not meet strict criteria for IBS
    • test for tissue transglutaminase IgA 1st
  • air sufflation during sigmoidoscopy often reproduces symptoms
  • not indicated for diagnosis
• colonoscopy
  • patients over age 45-50
  • recommended for severe or refractory symptoms
  • biopsy to rule out microscopic colitis
  • not indicated for diagnosis

Radiology

• plain abdominal radiograph if bloating or distention
• avoid computed tomography in the absence of red flags

Complications

• unnecessary surgery

Differential diagnosis

• colorectal carcinoma
• inflammatory bowel disease
• infectious colitis
• diverticulitis
• mesenteric ischemia
• diarrhea as predominant symptom
  • lactase deficiency
  • laxative abuse
  • malabsorption - celiac disease*
  • FODMAP sensitivity
  • hyperthyroidism
• constipation as predominant symptom
  • hypercalcemia
  • hypothyroidism
  • adverse effects of medications
• epigastric & periumbilical pain
  • peptic ulcer disease
  • gastritis
  • cholecystitis
  • pancreatitis
  • functional dyspepsia

* watch for celiac disease

• red flags will be present
• screening not routinely incidated

Management

• constipation
  • water soluble fiber: start psyllium 1 tbsp BID
    • number needed to treat - 7
  • osmotic laxative (polyethylene glycol)
  • stool softener: docusate (Colace) 100 mg BID
  • lubiprostone, a chloride channel activator, benefits a subset of women with IBS & constipation
  • linaclotide effective (treatment of choice in refractory IBS-C)
  • plecanatide
  • tenapanor reduces abdominal pain, discomfort, bloating, cramping,& fullnes
  • exercise
• diarrhea
  • trial of reduced lactose intake (< 8 oz or 240 mL of milk)
  • low FODMAP diet
    • low FODMAP diet superior to antispasmodic treatment
  • antispasmodic agents
    • belladona
    • dicyclomine (Bentyl)
  • antidiarrheal agents
    • loperamide (Imodium) 2-4 mg every 6-8 hours
    • diphenoxylate (Lomotil) 2.5-5 mg every 4-6 hours
  • fiber
  • tricyclic antidepressant as second line treatment
    • amitriptyline safe, well tolerated, effective
  • probiotics may be of benefit
    • number need to treat = 7
    • results inconsistent (MKSAP19)
  • alosetron withdrawn from U.S. market due to ischemic colitis
  • rifaximin may be effective
  • eluxadoline for IBS with diarrhea
  • fecal transplantation
    • no more effective than placebo in the treatment of IBS (MKSAP19)
• bloat
  • anticholinergics (1st line)
    • dicyclomine (Bentyl) 10-30 mg 30 min before meals
      • can cause constipation, rarely used with IBS-C
    • hyoscyamine
  • antidepressants: (adjunct therapy) begin at lower dose
    • tricyclic antidepressant may be helpful
      • amitriptyline (Elavil) 25-150 mg QHS
      • doxepin (Sinequan) 25-150 mg QHS
      • can cause constipation, rarely used with IBS-C
    • serotonin re-uptake inhibitor (SSRI)
      • fluoxetine (Prozac) 20 mg QD
      • paroxetine (Paxil): start 10 mg QD; titrate up to 40 mg QD
      • insufficient evidence of benefit
  • prokinetic agents:
    • cisapride (Propulsid) 10-20 mg BID (withdrawn by FDA)
    • metoclopramide (Reglan)
  • rifaximin (Xifaxan) has been found to be of benefit for selected patients, especially those with bloating & diarrhea
• proton-pump inhibitors or H2 blockers may benefit patients with diarrhea & urgency after meals
  • benefits should become apparent within 3 days
• complementary or alternative medicine
  • herbal therapy, dietary supplements, & mind-body therapy helpful for overall response.[34]
  • ony herbal therapy helpful for abdominal pain
• probiotics may be of some benefit
  • Bifidobacter infantis offers benefit to some patients with IBS & diarrhea
  • Lactobacillus may be of benefit
  • Lactobacillus GG not helpful in children; reduces frequency & severity of abdominal pain in children
• peppermint oil may be of benefit
• adjunctive cognitive behavior therapy may be helpful
  • symptom improvement after home-based or clinic-based CBT sustained for at least 1 year
• melatonin 3 mg QHS may be helpful
• patient education
  • stress may precipitate attacks
  • disorder is chronic, but without serious sequelae
• dietary management may be helpful:
  • avoid or limit the amount of gas-producing foods
    • beans, onions, broccoli, cabbage
  • avoid other foods that aggravate IBS symptoms
  • eat slowly
  • avoid overeating
  • avoid carbonated drinks
  • avoid lactose (lactose intolerance in 40% of IBS)
  • avoid large quantities of fructose or sorbitol
  • insoluble fiber (psyllium, wheat bran) may be of benefit
    • number needed to treat - 7
  • some patients improve on a wheat (gluten)-free diet
    • evidence for use in patients with IBS-D is inconclusive (MKSAP19)
  • low FODMAP diet may be of benefit
• IB-stim is an FDA-approved TENS device for IBS placed behind the ear
• up to 30% of patients resort to alternative medicine

Notes

• may be a genetic predisposition to respond to placebo

More general terms

• intestinal disease
• chronic gastrointestinal disease

Additional terms

• FODMAP (Fermentable, Oligo-, Di-, Monosaccharides, & Polyols)
• functional dyspepsia
• Rome criteria for irritable bowel syndrome

Patient information

irritable bowel syndrome patient information