What is the recommended treatment protocol and investigation for a patient with Irritable Bowel Syndrome (IBS)?

IBS Investigation and Treatment Protocol

Make a positive diagnosis of IBS based on symptoms using Rome criteria in patients without alarm features, then begin treatment with patient education, regular exercise, and symptom-directed therapy starting with dietary modifications and first-line medications. 1

Diagnostic Investigation

Initial Blood and Stool Testing

• Order full blood count, C-reactive protein or ESR, coeliac serology, and faecal calprotectin (in patients <45 years with diarrhea) to exclude organic disease. 1
• Follow local colorectal and ovarian cancer screening guidelines where indicated. 1

When to Avoid Colonoscopy

• Do not perform colonoscopy in typical IBS unless alarm features are present (unintentional weight loss ≥5%, rectal bleeding, fever, anemia, family history of colon cancer or IBD). 1
• Consider colonoscopy only in IBS-D patients with atypical features suggesting microscopic colitis: female sex, age ≥50 years, coexistent autoimmune disease, nocturnal or severe watery diarrhea, duration <12 months, weight loss, or use of NSAIDs/PPIs. 1

Specialized Testing for Atypical IBS-D

• Consider SeHCAT scanning or serum 7α-hydroxy-4-cholesten-3-one testing to exclude bile acid diarrhea in patients with nocturnal diarrhea or prior cholecystectomy. 1
• Consider anorectal physiology testing in patients with coexisting defecatory disorder or fecal incontinence to select candidates for biofeedback. 1

Tests to Avoid

• Do not test for exocrine pancreatic insufficiency, small intestinal bacterial overgrowth (hydrogen breath testing), or carbohydrate intolerance in typical IBS. 1
• Do not order IgG-based food allergy testing as true food allergy is rare in IBS. 1, 2

Patient Education and Expectations

Essential Explanation

• Explain IBS as a disorder of gut-brain interaction with a benign but relapsing/remitting course. 1, 3, 2
• Describe how the gut-brain axis is impacted by diet, stress, cognitive/behavioral/emotional responses, and post-infectious changes. 1
• Set realistic expectations: cure is unlikely, but substantial improvement in symptoms, social functioning, and quality of life is achievable. 1
• Address patient fears directly, particularly cancer concerns, rather than ordering extensive testing. 3, 2

Treatment Algorithm

Step 1: Universal Lifestyle Modifications (All Patients)

• Prescribe regular physical exercise as the foundation of treatment—benefits persist for years and improve constipation particularly. 1, 3, 2
• Advise balanced diet with adequate fiber, regular time for defecation, and proper sleep hygiene. 3, 2

Step 2: First-Line Dietary Therapy

Soluble Fiber (First-Line for All IBS)

• Start ispaghula (psyllium) at 3-4 g/day and build up gradually to avoid bloating—effective for global symptoms and abdominal pain. 1, 3, 2
• Avoid insoluble fiber (wheat bran) as it exacerbates symptoms, particularly bloating. 1, 3, 2

Low FODMAP Diet (Second-Line Dietary Therapy)

• Refer to a trained dietitian for supervised low FODMAP diet delivered in three phases: restriction, reintroduction, and personalization. 1, 2, 4
• This is effective for global symptoms and abdominal pain but requires professional supervision to avoid nutritional deficiencies. 1
• Consider avoiding strict FODMAP restriction in patients with moderate-to-severe anxiety or depression, as restrictive diets may worsen eating pathology. 3

Gluten-Free Diet

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

Step 3: First-Line Pharmacotherapy (Symptom-Directed)

For Abdominal Pain and Cramping

• Prescribe antispasmodics with anticholinergic properties (dicyclomine) as first-line therapy for abdominal pain, particularly when meal-related. 1, 3, 2, 5
• Consider peppermint oil as an alternative antispasmodic, though evidence is more limited. 1, 3, 2
• Common side effects include dry mouth, visual disturbance, and dizziness. 1

For IBS-D (Diarrhea-Predominant)

• Prescribe loperamide 2-4 mg up to four times daily (4-12 mg total daily) to reduce stool frequency, urgency, and fecal soiling. 1, 3, 2, 5
• Use prophylactically before going out or in divided doses throughout the day. 3, 2
• Titrate dose carefully as abdominal pain, bloating, nausea, and constipation are common side effects. 1
• Decrease fiber intake in IBS-D (opposite of IBS-C management). 5
• Identify and eliminate excessive lactose, fructose, sorbitol, caffeine, or alcohol intake. 5

For IBS-C (Constipation-Predominant)

• Continue soluble fiber supplementation as described above. 1, 3
• Add polyethylene glycol (osmotic laxative) for persistent constipation, titrating dose according to symptoms. 3

For IBS-M (Mixed Pattern)

• Prescribe tricyclic antidepressants as the most effective first-line pharmacological treatment for mixed symptoms. 3, 2
• Start amitriptyline 10 mg once daily at bedtime and titrate slowly to 30-50 mg once daily. 3
• Explain clearly that TCAs are used as gut-brain neuromodulators for pain modulation, not for depression. 3, 5
• Warn patients that side effects occur early and benefits may not appear for 3-4 weeks. 6
• TCAs are especially effective in diarrhea-predominant patients with disturbed sleep patterns but may worsen constipation. 6

Probiotics (Adjunctive Therapy)

• Trial probiotics for 12 weeks for global symptoms and bloating—no specific species or strain can be recommended. 1, 3, 2
• Discontinue if no improvement after 12 weeks. 1, 3, 2

Step 4: Second-Line Pharmacotherapy (Refractory Symptoms)

For Refractory IBS-D

• Prescribe rifaximin 550 mg three times daily for 14 days to improve abdominal pain and stool consistency. 5

For Refractory IBS-C

• Prescribe linaclotide for patients who fail to respond to laxatives. 7

Step 5: Psychological Therapies (Refractory Cases)

When to Refer

• Refer for IBS-specific cognitive behavioral therapy or gut-directed hypnotherapy when symptoms persist despite pharmacological treatment for 12 months. 3, 2, 5
• Consider earlier referral for patients with moderate-to-severe depression or anxiety, suicidal ideation, low social support, impaired quality of life, or avoidance behavior. 3, 5

Multidisciplinary Coordination

• Build collaborative links with gastroenterology dietitians for dietary management and gastropsychologists for brain-gut behavior therapies. 3, 2
• Inform the patient's referring doctor or mental health provider about any changes in wellbeing, particularly if there is risk of self-harm. 3

Treatment Monitoring and Adjustment

• Review treatment efficacy after 3 months and discontinue ineffective medications. 3, 5
• Adjust visit frequency to accommodate mental health needs and ongoing monitoring, as IBS often has significant psychological comorbidity. 3, 5
• The final decision regarding treatment choices should be made by the patient, with advice and support from the clinician. 1

Critical Pitfalls to Avoid

• Do not pursue colonoscopy or extensive testing once IBS diagnosis is established in patients under 45 without alarm features. 3, 2, 5
• Avoid opioids for chronic abdominal pain management due to risks of dependence and complications. 3
• Do not recommend IgG-based food allergy testing as true food allergy is rare in IBS. 3, 2
• Avoid excessive fiber supplementation as abdominal cramps and bloating may worsen. 6
• Do not use insoluble fiber (wheat bran) as it consistently worsens symptoms. 1, 3, 2

Referral to Gastroenterology

• Refer to gastroenterology when there is diagnostic doubt, severe or refractory symptoms despite first-line treatments, or when the patient requests specialist opinion. 1