Monday, May 29, 2023
HomeGastroenterologyIrritable Bowel Syndrome (IBS)

Irritable Bowel Syndrome (IBS)

Practice Essentials

Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) disorder characterized by abdominal pain and altered bowel habit in the absence of a specific and unique organic pathology, although microscopic inflammation has been documented in some patients.
Population-based studies estimate the prevalence of irritable bowel syndrome at 10%-20% and the incidence of irritable bowel syndrome at 1%-2% per year.

Signs and symptoms

Manifestations of IBS are as follows:

Altered bowel habit

Abdominal pain

Abdominal bloating/distention

Altered bowel habit in IBS may have the following characteristics:

Constipation variably results in complaints of hard stools of narrow caliber, painful or infrequent defecation, and intractability to laxatives

Diarrhea usually is described as small volumes of loose stool, with evacuation preceded by urgency or frequent defecation

Postprandial urgency is common, as is alternation between constipation and diarrhea

Characteristically, one feature generally predominates in a single patient, but significant variability exists among patients

Abdominal pain in IBS is protean, but may have the following characteristics:

Pain frequently is diffuse without radiation

Common sites of pain include the lower abdomen, specifically the left lower quadrant

Acute episodes of sharp pain are often superimposed on a more constant dull ache

Meals may precipitate pain

Defecation commonly improves pain but may not fully relieve it

Pain from presumed gas pockets in the splenic flexure may masquerade as anterior chest pain or left upper quadrant abdominal pain

Additional symptoms consistent with irritable bowel syndrome are as follows:

Clear or white mucorrhea of a noninflammatory etiology

Dyspepsia, heartburn

Nausea, vomiting

Sexual dysfunction (including dyspareunia and poor libido)

Urinary frequency and urgency have been noted

Worsening of symptoms in the perimenstrual period

Comorbid fibromyalgia

Stressor-related symptoms

Symptoms not consistent with irritable bowel syndrome should alert the clinician to the possibility of an organic pathology. Inconsistent symptoms include the following:

Onset in middle age or older

Acute symptoms (irritable bowel syndrome is defined by chronicity)

Progressive symptoms

Nocturnal symptoms

Anorexia or weight loss


Rectal bleeding

Painless diarrhea


Gluten intolerance

See Presentation for more detail.


The Rome IV criteria for the diagnosis of irritable bowel syndrome require that patients have had recurrent abdominal pain on average at least 1 day per week during the previous 3 months that is associated with two or more of the following

Related to defecation (may be increased or unchanged by defecation)

Associated with a change in stool frequency

Associated with a change in stool form or appearance

The Rome IV criteria (May 2016) only require abdominal pain in defining this condition; “discomfort” is no longer a requirement owing to its nonspecificity, and the recurrent abdominal pain.

Supporting symptoms include the following:

Altered stool frequency

Altered stool form

Altered stool passage (straining and/or urgency)


Abdominal bloating or subjective distention

Four bowel patterns may be seen with irritable bowel syndrome, and these remain in the Rome IV classification.
These patterns include the following:

IBS-D (diarrhea predominant)

IBS-C (constipation predominant)

IBS-M (mixed diarrhea and constipation)

IBS-U (unclassified; the symptoms cannot be categorized into one of the above three subtypes)

The usefulness of these subtypes is debatable. Notably, within 1 year, 75% of patients change subtypes, and 29% switch between constipation-predominant IBS and diarrhea-predominant IBS. The Rome IV criteria differ from the Rome III criteria in basing bowel habit on stool forms solely during days with abnormal bowel movements rather than on the total number of bowel movements.

A comprehensive history, physical examination, and tailored laboratory and radiographic studies can establish a diagnosis of irritable bowel syndrome in most patients. The American College of Gastroenterologists does not recommend laboratory testing or diagnostic imaging in patients younger than 50 years with typical IBS symptoms and without the following “alarm features”

Weight loss

Iron deficiency anemia

Family history of certain organic GI illnesses (eg, inflammatory bowel disease, celiac sprue, colorectal cancer)

Screening studies to rule out disorders other than IBS include the following:

Complete blood cell count with differential to screen for anemia, inflammation, and infection

A comprehensive metabolic panel to evaluate for metabolic disorders and to rule out dehydration/electrolyte abnormalities in patients with diarrhea

Stool examinations for ova and parasites, enteric pathogens, leukocytes, Clostridium difficile toxin, and possibly Giardia antigen

History-specific studies include the following:

Hydrogen breath testing to exclude bacterial overgrowth in patients with diarrhea and to screen for lactose and/or fructose intolerance

Tissue transglutaminase antibody testing and small bowel biopsy in IBS-D to diagnose celiac disease.

Thyroid function tests

Serum calcium testing to screen for hyperparathyroidism

Erythrocyte sedimentation rate and C-reactive protein measurement are nonspecific screening tests for inflammation

See Workup for more detail.


Management of irritable bowel syndrome consists primarily of providing psychological support and recommending dietary measures. Pharmacologic treatment is adjunctive and should be directed at symptoms.

Dietary measures may include the following:

Fiber supplementation may improve the symptoms of constipation and diarrhea

Polycarbophil compounds (eg, Citrucel, FiberCon) may produce less flatulence than psyllium compounds (eg, Metamucil)

Judicious water intake is recommended in patients who predominantly experience constipation

Caffeine avoidance may limit anxiety and symptom exacerbation

Legume avoidance may decrease abdominal bloating

Lactose, fructose, and/or FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) should be limited or avoided in patients with these contributing disorders

Probiotics are being studied for their use in decreasing IBS symptoms

Although the evidence is mixed regarding long-term improvement in GI symptoms with successful treatment of psychiatric comorbidities, the American College of Gastroenterology has concluded the following:

Psychological interventions, cognitive-behavioral therapy, dynamic psychotherapy, and hypnotherapy are more effective than placebo

Relaxation therapy is no more effective than usual care

Pharmacologic agents used for the management of symptoms in IBS include the following:

Anticholinergics/antispasmodics (eg, dicyclomine, hyoscyamine, trimebutine, peppermint oil)

Antidiarrheals (eg, diphenoxylate, loperamide)

Tricyclic antidepressants (eg, imipramine, amitriptyline)

Prokinetic agents

Bulk-forming laxatives

Serotonin receptor antagonists (eg, alosetron, tegaserod)

Chloride channel activators (eg, lubiprostone)

Guanylate cyclase C (GC-C) agonists (eg, linaclotide, plecanatide)

Altering bacterial flora and gas formation (eg, rifaximin)

Sodium-hydrogen exchange 3 (NHE3) inhibitors (eg, tenapanor)

See Treatment and Medication for more detail.

What is irritable bowel syndrome (IBS)? IBS is a condition that involves recurrent abdominal pain as well as abnormal bowel motility, which can include diarrhea and/or constipation.

Previous articleCNS Whipple Disease
Next articleCystinuria
- Advertisment -

Most Popular