Irritable Bowel Syndrome

Essentials of Diagnosis

• Common chronic functional disorder characterized by abdominal pain with alterations in bowel habits

• Symptoms usually begin in late teens to early twenties

• Limited evaluation is intended to exclude organic causes of symptoms

General Considerations

• No definitive diagnostic study

• Idiopathic clinical entity characterized by chronic (> 3 months) abdominal pain or discomfort that occurs in association with altered bowel habits that may be continuous or intermittent

• Abdominal discomfort or pain that has two of the following three features

  • Related to defecation

  • Associated with a change in frequency of stool

  • Associated with a change in appearance of stool (lumpy or hard; loose or watery)

• Other symptoms include

  • Abnormal stool passage (straining, urgency, or feeling of incomplete evacuation)

  • Abdominal bloating or feeling of abdominal distention

  • Other somatic or psychological complaints

Demographics

• Up to 10% of the adult population have symptoms compatible with irritable bowel syndrome, but most never seek medical attention

• Approximately two-thirds of diagnosed patients are women

Symptoms and Signs

• Subjective abdominal distention; visible distention not clinically evident

• Abdominal pain, intermittent, crampy, in the lower abdomen, that may be improved or worsened by defecation

• More frequent or less frequent stools with the onset of abdominal pain

• Looser stools or harder stools with the onset of pain

• Constipation, diarrhea, or alternating constipation and diarrhea

• Physical examination usually is normal

• Abdominal tenderness in the lower abdomen is common, but not pronounced

• Bloating, flatulence, and diarrhea may be exacerbated in some patients who eat poorly absorbed, fermentable, monosaccharides and short-chain carbohydrates ("FODMAPS")

Differential Diagnosis

• Colonic neoplasia

• Inflammatory bowel disease (ulcerative colitis, Crohn disease, microscopic colitis)

• Bile-acid diarrhea

• Hyperthyroidism or hypothyroidism

• Parasites

• Malabsorption (especially celiac disease, bacterial overgrowth, lactase deficiency)

• Causes of chronic secretory diarrhea (carcinoid)

• Gynecologic disorders (endometriosis, ovarian cancer)

• Psychiatric disorders (depression, panic disorder, and anxiety)

Physical examination

• Digital rectal examination should be performed in patients with constipation to screen for paradoxical anal squeezing during attempted straining that may suggest pelvic floor dyssynergia

• A pelvic examination is recommended for postmenopausal women with recent onset constipation and lower abdominal pain to screen for gynecologic malignancy

Laboratory Tests

• Complete blood count

• Fecal calprotectin level

• Serologic testing for celiac disease

• Stool specimen examinations should be obtained using nucleic acid amplification (PCR) tests

• Routine testing for bacterial overgrowth with hydrogen breath tests are not recommended

Diagnostic Procedures

• Routine sigmoidoscopy or colonoscopy is not recommended in young patients with symptoms of irritable bowel syndrome without alarm symptoms, but should be considered along with further laboratory testing in patients who do not improve with conservative management

• Colonoscopy

  • Obtain in all patients aged 50 years or older who have not had a previous evaluation

  • Random mucosal biopsies should be obtained to look for evidence of microscopic colitis

Medications

FOR ABDOMINAL PAIN, SPASM

• Antispasmodic (anticholinergic) agents are commonly used despite a lack of good evidence demonstrating efficacy

  • Dicyclomine, 10–20 mg three or four times daily orally

  • Hyoscyamine, 0.125 mg four times daily orally (or sublingually as needed)

  • Hyoscyamine, sustained-release 0.037 mg or 0.75 mg twice daily orally

  • Methscopolamine 2.5–5 mg orally before meals and at bedtime

• Tricyclic and related antidepressants

  • Nortriptyline, desipramine, or imipramine

    • Begin at 10 mg orally every night at bedtime

    • Increase gradually to 25–50 mg orally every night at bedtime as tolerated

  • Trazodone, beginning at 50 mg orally every night at bedtime, is an alternative

  • Not recommended for patients with predominant constipation

• Serotonin reuptake inhibitor antidepressants

  • Sertraline, 25–100 mg once daily orally

  • Fluoxetine, 10–40 mg once daily orally

  • Citalopram, 10–20 mg once daily orally

  • Paroxetine, 10–50 mg once daily orally

  • Not recommended for patients with predominant diarrhea

FOR DIARRHEA

• Antidiarrheal agents

  • Loperamide, 2 mg three or four times daily orally

  • Cholestyramine, 2–4 g orally with meals (off-label use)

  • Colesevelam, 625 mg, one to three tablets twice daily orally (off-label use)

  • Eluxadoline, 75–100 mg orally once daily

    • An opioid antagonist approved by the FDA in 2016

    • In phase III trials, abdominal pain was decreased and stool consistency was improved in ~ 25% of treated patients compared to 16–19% with placebo

    • However, sphincter of Oddi dysfunction and pancreatitis developed in a small number of patients

    • Given its limited efficacy, adverse side effect profile, and unproven benefit versus loperamide, further study is needed before its use can be recommended

  • Alosetron, 0.5–1 mg twice daily orally, for diarrhea as predominant symptom unresponsive to other conventional therapies

    • Restricted access in United States

    • May cause ischemic colitis in 4:1000 patients

FOR CONSTIPATION

• Fiber supplementation

  • Bran, psyllium, methylcellulose, or polycarbophil

  • May cause increased bloating

• Osmotic laxatives: polyethylene glycol 3350 (Miralax, 17–34 g/day) dissolved in fluid orally once daily

• Lubiprostone (8 mcg orally twice daily), linaclotide (290 mcg orally once daily), and plecanatide (3 mg orally once daily)

  • Approved for treatment of irritable bowel syndrome with constipation

  • Stimulate increased intestinal chloride and fluid secretion, resulting in accelerated colonic transit

FOR OTHER SYMPTOMS

• Ondansetron, 4–8 mg three times daily, showed overall excellent symptom improvement, including stool frequency, consistency, and urgency

• Rifaximin

  • May be considered in patients with refractory symptoms, especially bloating

  • Improvement may be attributable to suppression of bacteria in small intestine or colon

• In a randomized placebo-controlled crossover trial, ingestion of alpha-galactosidase supplement ("Beano") significantly improved bowel symptoms when taken with meals containing foods with high galactoside content (eg, beans, peas, lentils, soy)

• 2018 American College of Gastroenterology guideline

  • Poorly fermentable soluble fiber (psyllium, oatmeal) improves global symptoms in many patients

  • Fermentable or insoluble fiber (bran) may increase gas and bloating

  • Gluten-free diet is not recommended

  • Probiotics are weakly recommended

Therapeutic Procedures

• Reassure patient

• Explain functional nature of the symptoms

• Consider behavioral modification with relaxation techniques, hypnotherapy

• Recommend moderate exercise as helpful

• Restrict dietary "FODMAPS" (to improve bloating, flatulence, and diarrhea in some patients):

  • Fructose (corn syrups, apples, pears, honey, watermelon, raisins)

  • Lactose

  • Fructans (garlic, onions, leeks, asparagus, artichokes)

  • Wheat-based products (breads, pasta, cereals, cakes)

  • Sorbitol (stone fruits)

  • Raffinose (legumes, lentils, brussel sprouts, soybeans, cabbage)

Follow-Up

• Regular visits are helpful in reducing patient anxiety and overuse of the health care system

Prognosis

• Symptoms are usually chronic, but episodic; majority of affected patients learn to cope with them

When to Refer

• Persistent or worsening symptoms

• Signs of organic disease (blood per rectum, positive fecal occult blood, weight loss, severe abdominal pain)

• Signs of serious psychiatric disease or physical/sexual abuse

When to Admit

• Patients have increased rate of hospitalizations and inappropriate surgeries for abdominal pain