What is the recommended management for a patient with irritable bowel syndrome, including non‑pharmacologic measures, diet, and subtype‑specific pharmacologic therapy?

Management of Irritable Bowel Syndrome

Start all IBS patients with a clear explanation that IBS is a disorder of gut-brain interaction with a benign but relapsing/remitting course, followed by regular exercise and first-line dietary modifications, then escalate to symptom-specific pharmacotherapy based on the predominant bowel pattern. 1

Initial Patient Education and Diagnosis Confirmation

• Make a positive diagnosis based on Rome criteria without alarm features (rectal bleeding, anemia, unintentional weight loss ≥5%, nocturnal symptoms, fever, family history of colon cancer or inflammatory bowel disease), avoiding extensive testing in patients under 45 years old 1

• Explain directly that IBS is a gut-brain interaction disorder with excellent prognosis but expect symptom fluctuation over time, addressing specific patient fears about cancer or serious disease rather than ordering more tests 2, 3

• Check serological testing only for celiac disease; do not order C-reactive protein, fecal calprotectin, IgG food allergy panels, or hydrogen breath testing for small intestinal bacterial overgrowth as these have no role in typical IBS 1, 4

• Consider colonoscopy only if alarm features present or if patient has IBS-D with atypical features (nocturnal diarrhea, age ≥50 years, female sex, autoimmune disease, recent onset <12 months, or use of NSAIDs/PPIs) to exclude microscopic colitis 1

Universal First-Line Interventions (All Patients)

• Prescribe regular physical activity immediately as it provides significant benefit for all IBS symptoms, particularly constipation, with effects sustained at 5 years 1, 2

• Establish regular time for defecation and ensure adequate sleep hygiene 2, 3

Dietary Management Algorithm

Step 1: Initial Dietary Advice (All Patients)

• For IBS-C (constipation-predominant): Start soluble fiber (ispaghula/psyllium) at 3-4 g/day and gradually increase to avoid bloating; this improves global symptoms and abdominal pain 1, 5

• For IBS-D (diarrhea-predominant): Decrease fiber intake as it worsens diarrhea symptoms 2, 3

• Avoid insoluble fiber (wheat bran) in all IBS subtypes as it exacerbates symptoms, particularly bloating 1, 3

• Do not recommend gluten-free diet as evidence is insufficient 1

Step 2: Second-Line Dietary Therapy (If First-Line Fails)

• Refer to a trained dietitian for supervised low FODMAP diet delivered in three phases: restriction (4-6 weeks), systematic reintroduction, and personalization based on tolerance 1, 3

• Reintroduce FODMAPs according to tolerance to avoid unnecessary long-term dietary restriction 1

Pharmacological Treatment by Predominant Symptom

For Abdominal Pain and Cramping (All Subtypes)

• First-line: Use antispasmodics with anticholinergic properties (dicyclomine) before meals when pain is meal-related; warn patients about dry mouth, visual disturbance, and dizziness 1, 2, 5

• Alternative: Peppermint oil may be used as an antispasmodic, though evidence is more limited 3, 4

For IBS-D (Diarrhea-Predominant)

• First-line: Loperamide 4-12 mg daily, either regularly or prophylactically before going out, to reduce stool frequency, urgency, and fecal soiling; titrate dose carefully to avoid constipation, bloating, and nausea 1, 2, 3

• Second-line: Rifaximin 550 mg three times daily for 14 days is FDA-approved for IBS-D and reduces symptoms for up to 10 weeks post-treatment; repeat courses can be given if symptoms recur 6

For IBS-C (Constipation-Predominant)

• After soluble fiber fails, consider osmotic laxatives or secretagogues, though specific agents require specialist guidance 1, 5

For Mixed or Refractory Symptoms (All Subtypes)

• Tricyclic antidepressants (TCAs): Start amitriptyline 10 mg once daily at bedtime and titrate slowly to 30-50 mg once daily; explain these are used as gut-brain neuromodulators, not for depression; particularly effective for patients with insomnia, diarrhea-predominant symptoms, or refractory pain 1, 2

• SSRIs: Consider for constipation-predominant IBS or when TCAs are not tolerated, though evidence is weaker than for TCAs 1

• Counsel patients that side effects (dry mouth, drowsiness for TCAs; anxiety, sleep disturbance for SSRIs) occur early but benefits may not appear for 3-4 weeks 7

Probiotics

• Trial probiotics for 12 weeks for global symptoms and bloating; discontinue if no improvement, as no specific strain can be recommended 1, 3

Psychological Therapies (For Moderate-to-Severe or Refractory Cases)

• Refer to gastropsychologist for IBS-specific cognitive behavioral therapy or gut-directed hypnotherapy when symptoms persist despite pharmacological treatment for 12 months, or when symptoms are moderate-to-severe and patient accepts gut-brain dysregulation model 2, 3, 4

• Consider biofeedback specifically for patients with coexisting defecatory disorder or fecal incontinence 1, 5

Treatment Monitoring and Adjustment

• Review treatment efficacy after 3 months and discontinue ineffective medications 2, 5

• Recognize that IBS follows a relapsing-remitting course requiring periodic treatment adjustment 2, 3

Critical Pitfalls to Avoid

• Do not pursue extensive testing once IBS diagnosis is established in patients under 45 without alarm features, as this reinforces abnormal illness behavior and increases healthcare costs without benefit 2, 3, 5

• Do not order IgG-based food allergy testing as true food allergy is rare in IBS and these tests lack validity 3, 4

• Do not use insoluble fiber (wheat bran) as it consistently worsens symptoms 1, 3

• Do not test for exocrine pancreatic insufficiency or perform hydrogen breath testing for small intestinal bacterial overgrowth in typical IBS patients 1

Multidisciplinary Referral Criteria

• Refer to gastroenterology dietitian if patient consumes considerable intake of symptom-triggering foods, shows dietary deficits or nutritional deficiency, has recent unintended weight loss, or requests dietary modification advice 2, 3

• Refer to gastroenterology specialist when diagnostic doubt exists, symptoms are severe or refractory to first-line treatments, or patient specifically requests specialist opinion 1

• Screen for and address psychological comorbidities (anxiety, depression) as under-managed mental health conditions negatively affect IBS treatment response 2