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Basic Information ⬇

AUTHOR: Fred F. Ferri, MD

Definition

Irritable bowel syndrome (IBS) is a chronic functional disorder manifested by alteration in bowel habits and recurrent abdominal pain and bloating. IBS is a symptom complex influenced by a variety of physiologic determinants from gut to brain and back. The ROME IV criteria for diagnosis of IBS are:

  • Patient has recurrent abdominal pain ≥1 day per wk, on average, in the previous 3 mo, with an onset ≥6 mo before diagnosis.
  • Abdominal pain is associated with at least two of the following three symptoms:
    1. Pain related to defecation
    2. Change in frequency of stool
    3. Change in form (appearance) of stool
  • Patient has none of the following warning signs:
    1. Age ≥50 yr, no previous colon cancer screening, and presence of symptoms
    2. Recent change in bowel habit
    3. Evidence of overt GI bleeding (e.g., melena or hematochezia)
    4. Nocturnal pain or passage of stool
    5. Unintentional weight loss
    6. Family history of colorectal cancer or inflammatory bowel disease
    7. Palpable abdominal mass or lymphadenopathy
    8. Evidence of iron deficiency anemia on blood testing
    9. Positive test for fecal occult blood
  • The criteria must be fulfilled for at least the past 3 mo with symptom onset at least 6 mo before the diagnosis.
  • Table 1 subtypes IBS by predominant stool pattern.

TABLE 1 Subtyping Irritable Bowel Syndrome by Predominant Stool Pattern

  • IBS with constipation (IBS-C)-hard or lumpy stools∗≥25% and loose (mushy) or watery stools†≥25% of bowel movements‡
  • IBS with diarrhea (IBS-D)-loose (mushy) or watery stools†≥25% and hard or lumpy stool∗≥25% of bowel movements‡
  • Mixed IBS-hard or lumpy stools∗≥25% and loose (mushy) or watery stools†≥25% of bowel movements‡
  • Unsubtyped IBS (IBS unclassified)-insufficient abnormality of stool consistency to meet criteria for IBS with constipation, diarrhea, or mixed‡

IBS, Irritable bowel syndrome.

∗Bristol Stool Form Scale 1-2 (separate hard lumps like nuts [difficult to pass] or sausage-shaped but lumpy).

† Bristol Stool Form Scale 6-7 (fluffy pieces with ragged edges, a mushy stool or watery, no solid pieces, entirely liquid).

‡ In the absence of use of antidiarrheals or laxatives.

Adapted from Sayuk GS, Gyawali CP: Irritable bowel syndrome: modern concepts and management options, Am J Med 128(8):817-827, 2015.

Synonyms

Irritable colon

Spastic colon

IBS

ICD-10CM CODES
K58Irritable bowel syndrome
K58.9Irritable bowel syndrome without diarrhea
K58.0Irritable bowel syndrome with diarrhea
Epidemiology & Demographics

  • IBS is the most common functional bowel disorder. An estimated 15 million people in the U.S. have IBS.
  • IBS occurs in 7% to 21% of the general population of industrialized countries and is responsible for >50% of gastrointestinal (GI) referrals. Worldwide adult prevalence is 12%. Incidence increases during adolescence and peaks in third and fourth decades of life.
  • Female:male ratio is 2:1. Peak prevalence is from 20 to 39 yr of age.
  • Nearly 50% of patients have psychiatric abnormalities, with anxiety disorders being most common.
Physical Findings & Clinical Presentation

  • The clinical presentation of IBS consists of abdominal pain and abnormalities of defecation, which may include loose stools, usually after meals and in the morning, alternating with episodes of constipation.
  • Physical examination is generally normal.
  • Nonspecific abdominal tenderness and distention may be present.
Etiology

  • Unknown, believed to be multifactorial. Fig. 1 illustrates a biopsychologic model of IBS pathophysiology.
  • Associated pathophysiology includes altered GI motility, alteration in gut flora, and increased gut sensitivity.
  • Risk factors: Anxiety, depression, personality disorders, history of childhood sexual abuse, and domestic abuse in women.

Figure 1 A biopsychosocial model of irritable bowel syndrome pathophysiology.

!!flowchart!!

Irritable bowel syndrome is thought to be a multifactorial disorder, deriving from a potential multitude of etiopathogenic factors, including environmental, psychological, and physiologic factors. This model highlights the complex, often bidirectional interplay of these factors in the experience of irritable bowel syndrome symptoms. cGMP, Cyclic guanosine monophosphate; 5-HT3, serotonin type 3; 5-HT4, serotonin type 4; FODMAPS, fermentable oligosaccharides, disaccharides, monosaccharides, and polyols; GI, gastrointestinal; H20, water; HRQOL, health-related quality of life; IBS, irritable bowel syndrome.

Modified from Sayuk GS, Gyawali CP: Irritable bowel syndrome: modern concepts and management options, Am J Med 128(8):817-827, 2015.

Diagnosis ⬆ ⬇

Differential Diagnosis

  • Inflammatory bowel disease (IBD)
  • Diverticulitis
  • Colon malignancy
  • Endometriosis
  • Peptic ulcer disease
  • Biliary liver disease
  • Chronic pancreatitis
  • Constipation caused by medications (opiates, calcium channel blockers, anticholinergics)
  • Diarrhea caused by medications (metformin, colchicine, proton pump inhibitors, antacids, antibiotics)
  • Small-bowel overgrowth
  • Celiac disease
  • Parasites
  • Lymphoma of GI tract
  • Pelvic floor dyssynergia
Workup

Diagnostic workup (Table 2) is aimed primarily at excluding the conditions listed in the differential diagnoses. A step-wise approach is critical. It is important to identify red flags of other diseases, such as weight loss, rectal bleeding, onset in patients >50 yr, fever, nocturnal pain, and family history of malignancy or IBD. Additional red flags include abnormal examination (e.g., mass, enlarged lymph nodes, stool positive for occult blood, muscle wasting) and abnormal laboratory values (anemia, leukocytosis, abnormal chemistry).

TABLE 2 Irritable Bowel Syndrome Treatment Strategy: A Way Forward

  1. Evaluation
    1. Consider conditions that mimic IBS (e.g., celiac disease, microscopic colitis, bile acid diarrhea, pancreatic insufficiency, carbohydrate intolerances, medication side effects, postsurgical neoanatomy)
    2. Assess for the presence of alarm symptoms
    3. Evaluate for symptom triggers (e.g., stressors, diet)
    4. Explore presence of other functional GI (e.g., functional dyspepsia) and non-GI disorders (e.g., fibromyalgia), psychiatric comorbidity, and drug intolerances
    5. Understand previous IBS treatment experiences
  2. Selection of treatment approach
    1. Predicated on symptom severity and dominant symptoms
    2. Symptom severity (intensity, bother, effects on quality of life)
      1. Mild symptoms, intermittent symptoms, low symptom burden: Symptomatic or peripheral therapy
      2. Moderate symptoms: Centrally acting neuromodulators, especially if symptomatic therapy does not provide adequate benefit
      3. Severe symptoms and those with comorbidities (non-GI functional disorders, psychiatric): Both centrally acting neuromodulators and peripheral therapy
    3. Concurrent affective disorders need to be managed
    4. Other central therapies (cognitive and behavioral therapy, hypnosis, stress reduction) may need to be considered
    5. Dominant symptoms (diarrhea, constipation, pain, other GI symptoms)
      1. Constipation predominant
    6. Laxatives, fiber
    7. Novel agents (linaclotide, lubiprostone)
      1. Diarrhea predominant
    8. Antidiarrheals
    9. Alosetron
    10. Address dysbiosis (rifaximin, probiotics)
    11. Diet (low FODMAP)
    12. Bile binders (cholestyramine, colesevelam)
    13. Disaccharidases (lactase)
      1. Pain predominant
    14. Antidepressants (TCAs and SNRIs preferred)
    15. Linaclotide when constipation present
    16. Avoid narcotics
  3. Education and therapeutic alliance
    1. Inform patient about etiopathogenesis
    2. Reaffirm legitimacy of diagnosis; allay concerns about organic disease
    3. Provide information about support organizations (International Foundation for Functional Gastrointestinal Disorders)

FODMAP, Fermentable oligosaccharides, disaccharides, monosaccharides, and polyols; GI, gastrointestinal; IBS, irritable bowel syndrome; SNRI, serotonin-norepinephrine reuptake inhibitor; TCA, tricyclic antidepressant.

Laboratory Tests

  • Blood work is generally normal. CBC is reasonable to evaluate for anemia. The presence of anemia should alert to the possibility of a colonic malignancy or IBD.
  • Other reasonable tests include C-reactive protein, tissue transglutaminase antibody (rule out celiac disease), and TSH (rule out thyroid abnormalities).
  • Fecal calprotectin level is useful to differentiate IBS from inflammatory bowel disease in patients who have IBS with diarrhea or with both diarrhea and constipation. Fecal calprotectin levels less than 40 mcg/g exclude IBD in patients with IBS.
  • Testing of stool for ova and parasites should be considered only in patients with chronic diarrhea. Evaluation of stool for Clostridium difficile may be helpful in patients with predominant diarrhea symptoms who have recently taken antibiotics.
Imaging Studies

  • Imaging studies (e.g., flat and upright abdominal radiograph, small-bowel series, sonogram or CT of abdomen and pelvis) are normal and not necessary for diagnosis.
  • Lower endoscopy is generally normal except for the presence of some spasms. Colonoscopic imaging should be performed only in persons who have alarm features to rule out organic disease and in persons older than 50 yr to screen for colorectal cancer.

Treatment ⬆ ⬇

Nonpharmacologic Therapy

  • The patient should be encouraged to maintain an adequate fiber intake and to eliminate foods that aggravate symptoms. Avoidance of caffeine, dairy products, fatty foods, and dietary excesses is also helpful. Several clinical trials have shown that a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) improves symptoms in nearly 70% of patients with IBS.1a
  • Cognitive-behavioral therapy is also recommended, particularly in younger patients, because psychosocial stressors are important triggers of IBS. Reassurance that the disorder is benign and education about trigger avoidance and stress management are important.
  • Importance of regular exercise and adequate fluid intake should be stressed.
  • Fig. E2 illustrates the management of IBS.

Figure E2 Management of irritable bowel syndrome.

!!flowchart!!

CBC, Complete blood count; IBS, irritable bowel syndrome.

Modified from Palmer KR, Penman ID: 22 Alimentary tract and pancreatic disease. In Colledge NR et al [eds]: Davidson’s principles and practice of medicine, Philadelphia, 2010, Elsevier.

General Rx

  • The mainstay of treatment of IBS is diet. A FODMAP diet has been proven effective. Fiber is helpful for relief of constipation but not for relief of pain. Because symptoms are chronic, the use of laxatives should generally be avoided.
  • Soluble fiber (psyllium) is more effective in symptom relief than insoluble fiber (bran). Fiber supplementation with psyllium 1 tbsp bid or calcium polycarbophil (FiberCon) 2 tablets one to four times daily followed by 8 oz of water may be necessary in some patients.
  • Patients should be instructed that there might be some increased bloating on initiation of fiber supplementation, which should resolve within 2 to 3 wk. It is important that patients take these fiber products on a regular basis and not only as needed. Fiber is not effective in patients with diarrhea-predominant IBS and may worsen symptoms in these patients.
  • Patients who appear anxious can benefit from use of sedatives or selective serotonin reuptake inhibitors (SSRIs). Tricyclic antidepressants in low doses are also effective in some patients with diarrhea-predominant IBS.
  • C-2 chloride channel activators: Lubiprostone (Amitiza) is a chloride channel activator that stimulates chloride-rich intestinal fluid secretion and accelerates small intestine and colonic transmit time. It may be effective in chronic constipation-predominant IBS unresponsive to conventional treatment. Usual dose is 8 to 24 mcg bid with food. Side effects include headache and nausea.
  • Linaclotide (Linzess) is a guanylate cyclase-C (GC-C) agonist FDA approved for IBS with constipation. It stimulates secretion of chloride and bicarbonate into the intestinal lumen, mainly through activation of the CFTR ion channel, resulting in increased intestinal fluid and accelerated transit. Usual dose for IBS is 290 mcg 30 min before eating. The most common adverse effects are diarrhea, abdominal pain, flatulence, and abdominal distension.
  • Tenapanor (Ibsrela) is an FDA-approved sodium/hydrogen exchanger 3 (NHE3) for twice daily oral treatment of IBS with constipation in adults. Its mechanism of action involves decreasing absorption of sodium, increasing osmotic secretion of water into the gut, shortening intestinal transit time, and softening stool consistency.1
  • Loperamide is effective for diarrhea. Alosetron, a serotonin type-3 receptor antagonist previously withdrawn because of severe constipation and ischemic colitis, has been reintroduced with limited availability. It is indicated only for women with severe chronic diarrhea-predominant IBS unresponsive to conventional therapy and not caused by anatomic or metabolic abnormality. Starting dose is 1 mg qd.
  • Eluxadoline (Viberzi) is an FDA-approved μ-opioid receptor agonist and Δ-opioid receptor antagonist for IBS with diarrhea. It decreases muscle contractility, inhibits water and electrolyte secretion, and increases rectal sphincter tone. Usual dose is 100 mg PO bid taken with food.
  • Alterations in gut flora have been identified as potentially contributing to IBS (84% of IBS patients have an abnormal lactulose breath test, suggesting small-intestinal bacterial overgrowth). Rifaximin, a gut-selective antibiotic, has been used in recent trials to eradicate bacterial overgrowth (70% eradication rate). A dose of 400 mg tid for 10 days was reported effective in improving IBS symptoms up to 10 wk after discontinuation of therapy. Until additional evidence is available, use of rifaximin or other antibiotics in IBS should be reserved for patients with proven bacterial overgrowth.
  • Antispasmodics-anticholinergics (e.g., dicyclomine, hyoscyamine) are often used, but efficacy data from clinical trials are inconclusive.
  • Probiotics: Bifidobacteria and some combinations of probiotics have shown some limited efficacy. Lactobacilli do not appear to be effective for the treatment of IBS. Additional data showing efficacy is needed before probiotics can be endorsed for treatment of IBS.
  • Antidepressants: SSRIs are more effective than placebo for relief of global IBS symptoms.
Disposition

More than 60% of patients respond successfully to treatment over the initial 12 mo; however, IBS is a chronic, relapsing condition and requires prolonged therapy.

Referral

GI referral is recommended in patients with rectal bleeding, fever, nocturnal diarrhea, anemia, weight loss, or onset of symptoms >40 yr. Consultation is also necessary if specialized diagnostic procedures such as endoscopy are necessary.

Pearls & Considerations ⬆ ⬇

Comments

  • Patients should be educated regarding maintenance of a high-fiber diet and elimination of stressors, which can precipitate attacks of IBS. They should be reassured that their condition does not lead to cancer.
  • Recent drug efforts (alosetron, tegaserod) are aimed at serotonergic receptors in the gut because most of the serotonin in the body is found in the GI tract and is believed to be involved in the mediation of visceral sensation and motility.
  • Cognitive-behavioral therapy is effective in the treatment of patients with IBS and should be considered as part of the armamentarium against this disorder.
  • Some patients with IBS but without celiac disease show symptom improvement on a wheat-free diet. A 2- to 3-wk trial of wheat avoidance may be reasonable in patients with treatment-resistant IBS.
  • Fecal microbiota transplantation (FMT) delivered via upper endoscopy seems to be efficacious in improving symptoms in all IBS subtypes in early clinical trials.
Related Content

Irritable Bowel Syndrome (Patient Information)

Related Content ⬆

    1. Carbone F : Diet or medication in primary care patients with IBS: the DOMINO study - a randomised trial supported by the Belgian Health Care Knowledge Centre (KCE Trials Programme) and the Rome Foundation Research InstituteGut. ;71(11):2226-2232, 2022.
    2. Chey W.D. : Efficacy of tenapanor in treating patients with irritable bowel with constipation: a 26 week, placebo-controlled phase 3 trial (T3MPO-2)Am J Gastroenterology. ;116, 2021.
    3. Camiueri M. : Peripheral mechanisms in irritable bowel syndromeN Engl J Med. ;367:1626-1635, 2012.
    4. Carroccio A. : Non-celiac wheat sensitivity diagnosed by double-blind placebo-controlled challenge: exploring a new clinical entityAm J Gastroenterol. ;107:1898-1906, 2012.
    5. Chey W.D. : Irritable bowel syndrome: a clinical reviewJ Am Med Assoc. ;313(9):949-958, 2015.
    6. Dugum M. : Managing irritable bowel syndrome: the low-FODMAP dietCleve Clin J Med. ;83:655-662, 2016.
    7. El-Salhy M. : Efficacy of faecal microbiota transplantation for patients with irritable bowel syndrome in a randomised, double-blind, placebo-controlled studyGut. ;69:859-867, 2020.
    8. Ford A.C. : Irritable bowel syndromeN Engl J Med. ;376:2666-2678, 2017.
    9. Lembo A.J. : Eluxadoline for irritable bowel syndrome with diarrheaN Engl J Med. ;374:242-253, 2016.
    10. Marteaus P. : Probiotics in functional intestinal disorders and IBS: proof of action and dissecting the multiple mechanismsGut. ;59:285-286, 2010.
    11. Mearin F. : Bowel disordersGastroenterology. ;150:1393-1407, 2016.
    12. Pimentel M. : Rifaximin therapy for patients with irritable bowel syndrome without constipationN Engl J Med. ;364:22-32, 2011.
    13. Rao V.L. : Pharmacologic management of irritable bowel syndromeJ Am Med Assoc. ;314:2684-2685, 2015.
    14. Sayuk G.S., Gyawali C.P. : Irritable bowel syndrome: modern concepts and management optionsAm J Med. ;128:817-827, 2015.
    15. Simrén M. : Management of the multiple symptoms of irritable bowel syndromeLancet Gastroenterol Hepatol. ;2(2):112-122, 2017.
    16. Wilkins T. : Diagnosis and management of IBS in adultsAm Fam Physician. ;86(5):419-426, 2012.