- Clinical science
Irritable bowel syndrome (IBS) is a common chronic condition affecting 20–50% of patients with gastrointestinal complaints. The exact pathophysiology is unknown, but may involve changes in gastrointestinal motility, visceral hypersensitivity, and altered gastrointestinal permeability. The condition presents with recurrent, non‑specific changes in bowel movements (e.g., diarrhea and/or constipation) and abdominal symptoms (e.g., diffuse pain, pressure). The Rome IV diagnositc criteria, which are based on alterations in bowel habits, are used to diagnose IBS. Laboratory studies and imaging reveal no abnormalities. Treatment consists of dietary modifications and administration of symptom‑based medication (antidiarrheals, laxatives, antispasmodics).
- Prevalence: 10–20% in North America and Europe (accounts for 20–50% of referrals to gastroenterologists)
- Sex: : In Western countries, women are 1.5–2 times more likely to be affected than men.
- Age: Approx. 50% of cases are reported in individuals younger than 35.
Epidemiological data refers to the US, unless otherwise specified.
IBS is defined as a functional gastrointestinal disorder without a specific organic cause. The underlying pathophysiology of IBS is not yet fully understood. The following pathophysiological hypotheses describe the most common findings associated with IBS, though these may not be present in every case.
- Altered gastrointestinal motility
- Visceral hypersensitivity/hyperalgesia
- Increased perception of physiological intestinal movements
Pain caused by hypersensitivity to
- Balloon distention of the intestine (sudden, rather than gradual, distention)
- Abdominal bloating
- Altered permeability of the gastrointestinal mucosa
- Possibly mild intestinal inflammation
- Altered intestinal microflora
- Food sensitivity
- Psychosocial aspects
- Increased occurrence of IBS in patients with depression, anxiety, phobias, somatization
- Conversely, patients with IBS report higher levels of stress
IBS is characterized by chronic abdominal pain and changes in bowel habits – both of which are typical, but not specific, symptoms of the condition.
- Frequency, intensity, and localization generally vary widely from patient to patient
- Typically alleviated by defecation
- Altered bowel habits: diarrhea and/or constipation
Other gastrointestinal symptoms
- Nausea, reflux, early satiety
- Passing of mucus, abdominal bloating
- Extraintestinal symptoms
- Physical examination: normal
IBS is a clinical diagnosis; based on the patient's history (Rome IV criteria) and symptoms. However, any suspected differential diagnoses should be ruled out before making a definitive diagnosis.
- Rome IV criteria for irritable bowel syndrome: diagnosis can be made if the following criteria are present
- Other symptoms consistent with IBS (see "Symptoms/clinical findings")
- A family history of inflammatory bowel disease, celiac disease, or colorectal cancer is unusual in patients with IBS.
Ruling out organic disease
If no other differential diagnosis is suspected, laboratory tests and imaging are generally not recommended for individuals under the age of 50 if they show typical signs of IBS and lack any alarming signs, such as iron-deficiency anemia, weight loss, or a family history of organic gastrointestinal diseases.
- Laboratory tests: normal in IBS
Stool analysis: normal in IBS
- No blood or leukocytes
- Negative cultures and parasites
- Hydrogen breath test: to rule out lactose or fructose tolerance test http://goo.gl/7Mb2ah
- Normal colonic mucosa on colonoscopy
- Other imaging includes abdominal ultrasound, barium studies, CT
|General appearance||Pain||Stool habits|
|Irritable bowel syndrome|| || |
|Crohn's disease|| || |
|Ulcerative colitis|| || || |
|Colorectal carcinoma|| || |
Other differential diagnoses to consider
- Bacterial or viral gastroenteritis
- Bacterial overgrowth syndrome
- Functional diarrhea
The differential diagnoses listed here are not exhaustive.
- Regular consultations and reassurance that the disease, although chronic, is benign
- Dietary adjustments
- Physical activity
- Stress management (identification of stress factors, avoidance techniques, relaxation therapy)
- Psychological therapy (patients with psychological conditions): e.g., cognitive-behavioral therapy
Medical therapy of IBS is symptom‑directed:
- Antidiarrheals (loperamide)