Irritable Bowel Syndrome



  • A gastrointestinal (GI) disorder characterized by chronic and recurrent abdominal pain, discomfort, bloating, distension, and alteration in bowel habits in the absence of an organic cause
  • May be characterized as diarrhea-predominant (IBS-D),constipation-predominant (IBS-C), mixed (IBS-M), or unknown (IBS-U); may alternate between symptoms
  • Synonym(s): spastic colon; irritable colon


Irritable bowel syndrome (IBS) accounts for 30–50% of visits to gastroenterologists and ~2 million primary care visits annually in United States with estimated cost of $1.5 to $10 billion dollars a year.

2 per 1,000 person years

Pooled estimate of ~4% globally using Rome IV criteria or 9% globally using Rome III criteria

  • Predominant age: 20 to 39 years
  • If age >50 years, consider other diagnoses.
  • In the United States, female > male (3:1)
  • More common in low socioeconomic communities

Etiology and Pathophysiology

  • The etiology is unknown; associated with abnormalities of intestinal motility and enhanced sensitivity to visceral stimuli. The trigger may be luminal or environmental.
  • PI-IBS (post-infectious) develops in roughly 10% with infectious enteritis.
  • The role of food sensitivity, microbiome dysbiosis, genetic, and psychosocial causes including early childhood stress are under investigation.
  • Increase in mast cell density and activity has been demonstrated on biopsy from terminal ileum, jejunum, and colon in patients with IBS and may correlate with visceral hypersensitivity (1).
  • Current investigation is ongoing regarding low-grade mucosal and neuroinflammation, and the contribution of this inflammation in the dysregulation of the “brain-gut” axis (1).

Unknown. IBS tracks in some families, relatives of someone with IBS are 2 to 3 times more likely to have IBS.

Risk Factors

  • Female sex, odds ratio 1.67
  • Other family members with similar GI disorder
  • Psychological factors: stress, abuse history, anxiety, depression or somatization
  • Somatic factors: GI infection, pain syndromes, obesity, antibiotic use, and abdominal surgery
  • Social factors: socioeconomic status in childhood, family history

Pediatric Considerations
No risk to mother or fetus

General Prevention

See “Diet.”

Commonly Associated Conditions

  • Other functional GI disorders (heartburn, dyspepsia, gastroesophageal reflux disease, nausea, diarrhea, incontinence, pelvic floor dyssynergia, and constipation)
  • Chronic conditions including migraines, fibromyalgia, chronic pelvic pain, temporomandibular joint dysfunction, chronic fatigue syndrome, sleep disorders, and overactive bladder
  • Psychiatric disorders: major depression, anxiety, somatoform disorders, and posttraumatic stress

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