Irritable Bowel Syndrome

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Description

  • A chronic functional brain-gut disorder characterized by chronic and recurrent abdominal pain and altered bowel habits in the absence of an organic cause; more common in patients aged <50 years and in women
  • May be characterized as diarrhea-predominant (IBS-D), constipation-predominant (IBS-C), mixed (IBS-M), or unclassified (IBS-U); may alternate between symptoms

Epidemiology

Irritable bowel syndrome (IBS) accounts for 25–50% of visits to gastroenterologists and ~2 million primary care visits annually in United States with estimated cost of $1.5 to 10 billion/year.

Incidence

1–2% per year

Prevalence

  • Pooled estimate of ~4% globally using Rome IV criteria or 10% globally using Rome III criteria
  • Predominant age: 20 to 39 years. If age >50 years, consider other diagnoses. In the United States, affects 10–15% of the population. In the United States, female > male (3:1). Females more likely to have IBS-C as compared to males.
  • More common in low socioeconomic communities

Etiology and Pathophysiology

  • IBS pathophysiology is multifactorial and complex; linked to abnormal motility, inflammation, alterations in the gut microbiome, and increased visceral sensitivity. Triggers may include luminal contractions, delayed transit, or environmental factors.
  • Postinfectious IBS (PI-IBS) occurs in ~10% after infectious enteritis. Risk is 6 times higher postinfection. Causes may include malabsorption, increased enteroendocrine cells/lymphocytes or antibiotic use.
  • Food sensitivity, microbiome dysbiosis, genetic, and psychosocial causes including early childhood stress are under study. Biopsies show increased mast cell and lymphocyte activity in the ileum, jejunum, and colon, possibly tied to visceral hypersensitivity (1).
  • Elevated pro-inflammatory cytokines are observed and may reflect gut inflammation.
  • Ongoing studies are exploring low-grade mucosal/neural inflammation and its role in “brain-gut” axis dysfunction (1).

Genetics

Unknown; some studies suggest a genetic susceptibility relatives of someone with IBS are 2 to 3 times more likely to have IBS. Further research is still required.

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 childhoodPediatric Considerations
No risk to mother or fetus

General Prevention

See “Diet” section.

Commonly Associated Conditions

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

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