Irritable Bowel Syndrome Practice Essentials

Irritable bowel syndrome (IBS) is a functional GI disorder characterized by abdominal pain and altered bowel habits in the absence of specific and unique organic pathology, although microscopic inflammation has been documented in some patients.[2] 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 habits, Abdominal pain, Abdominal distention
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 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

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
Fever
Rectal bleeding
Painless diarrhea
Steatorrhea
Lactose and/or fructose intolerance
Gluten intolerance

Diagnosis
The Rome III criteria for the diagnosis of irritable bowel syndrome[3] require that patients have had recurrent abdominal pain or discomfort at least 3 days per month during the previous 3 months that is associated with 2 or more of the following:

Relieved by defecation
Onset associated with a change in stool frequency
Onset associated with a change in stool form or appearance
Supporting symptoms include the following:
Altered stool frequency
Altered stool form
Altered stool passage (straining and/or urgency)
Mucorrhea
Abdominal bloating or subjective distention
Four bowel patterns may be seen with irritable bowel syndrome. These patterns include the following:

IBS-D (diarrhea predominant)
IBS-C (constipation predominant)
IBS-M (mixed diarrhea and constipation)
IBS-A (alternating diarrhea and constipation)
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.

A comprehensive history, a 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”[4] :

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 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 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
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 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 and/or fructose should be limited or avoided in patients with these contributing disorders
Although 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 management of symptoms in IBS include the following:

Anticholinergics (eg, dicyclomine, hyoscyamine)
Antidiarrheals (eg, diphenoxylate, loperamide)
Tricyclic antidepressants (eg, imipramine, amitriptyline)
Prokinetics
Bulk-forming laxatives
Serotonin receptor antagonists (eg, alosetron)
Chloride channel activators (eg, lubiprostone)
Guanylate cyclase C (GC-C) agonists (eg, linaclotide)
Antispasmodics (eg, peppermint oil, pinaverium, trimebutine, cimetropium/dicyclomine)[5]