What is the initial workup and treatment approach for a patient with irritable bowel syndrome (IBS)?

Initial Workup and Treatment Approach for Irritable Bowel Syndrome (IBS)

The initial workup for IBS should include a detailed history focusing on cardinal symptoms, limited baseline investigations (full blood count, CRP/ESR, coeliac serology, and faecal calprotectin if diarrhea is present), followed by a positive diagnosis and a stepwise treatment approach targeting predominant symptoms. 1

Diagnostic Approach

History Taking

• Focus on cardinal symptoms:
  • Abdominal pain
  • Altered bowel habits (abnormal stool frequency/consistency)
  • Relationship between pain and bowel movements (pain relieved or exacerbated by defecation)
• Document onset and duration of symptoms
• Assess for potential triggers:
  • Post-infection onset
  • Recurrent antibiotic use
  • Acute or chronic stress/psychological trauma
• Evaluate extraintestinal symptoms (back pain, urological, gynecological)
• Screen for comorbidities (psychological conditions, other functional disorders)
• Review medication history (especially opioids)
• Assess for alarm features that warrant further investigation:
  • Unintentional weight loss
  • Rectal bleeding
  • Family history of colorectal cancer or IBD
  • Onset of symptoms after age 50

Baseline Investigations

• Full blood count
• C-reactive protein or erythrocyte sedimentation rate
• Coeliac serology
• Faecal calprotectin (if diarrhoea present and age <45 years) 1

Treatment Algorithm

Step 1: Patient Education and Dietary Modifications

• Explain IBS as a disorder of gut-brain interaction
• Reassure about benign prognosis but acknowledge chronic, relapsing nature
• Implement dietary changes:
  • Establish baseline fiber intake
  • For IBS-C: Increase soluble fiber intake
  • For IBS-D: Decrease fiber intake
  • Consider trial of lactose/fructose/alcohol exclusion if appropriate
  • Consider low FODMAP diet for moderate to severe symptoms (under dietitian supervision) 1

Step 2: First-Line Pharmacological Treatment Based on Predominant Symptom

• For abdominal pain:

  • Antispasmodics (e.g., dicyclomine) 1
  • Peppermint oil

• For diarrhea (IBS-D):

  • Loperamide 4-12 mg daily (regularly or prophylactically)
  • Consider cholestyramine if bile acid malabsorption suspected 1

• For constipation (IBS-C):

  • Soluble fiber supplements (ispaghula/psyllium)
  • Osmotic laxatives (polyethylene glycol) 1

• For bloating:

  • Reduce intake of gas-producing foods
  • Trial of dietary modifications (reduce fiber/lactose/fructose) 1

Step 3: Second-Line Treatments for Persistent Symptoms

• For persistent abdominal pain:

  • Low-dose tricyclic antidepressants (e.g., amitriptyline 10-50 mg at bedtime)
    • Start with 10 mg and titrate by 10 mg weekly
    • Target dose 25-50 mg at bedtime 2
    • Avoid in patients with severe constipation

• For persistent diarrhea:

  • Consider rifaximin (antibiotic)
  • For severe IBS-D: Consider alosetron (5-HT3 antagonist) in women with severe symptoms 3

• For persistent constipation:

  • Consider linaclotide (guanylate cyclase-C agonist)
    • Shown to improve abdominal pain and increase CSBMs in IBS-C 4

Step 4: Psychological Interventions

• For moderate to severe symptoms or when stress is a significant factor:
  • Cognitive behavioral therapy
  • Gut-directed hypnotherapy
  • Mindfulness-based stress reduction 2

Important Clinical Considerations

Common Pitfalls to Avoid

1. Treating IBS as a diagnosis of exclusion - IBS should be positively diagnosed using symptom-based criteria and limited investigations 5
2. Overinvestigation - Extensive testing is unnecessary in patients who meet diagnostic criteria and lack alarm features
3. Focusing solely on bowel symptoms - Remember to address pain, psychological factors, and quality of life
4. Using opioid analgesics - These can worsen GI dysmotility and should be avoided for chronic abdominal pain 2
5. Promising a cure - Set realistic expectations that treatments aim to improve quality of life rather than cure the condition 1

Follow-up and Monitoring

• Review efficacy after 3 months of treatment
• Discontinue ineffective treatments
• Adjust treatment based on symptom evolution
• Consider referral to gastroenterology when:
  • Diagnostic uncertainty exists
  • Symptoms are severe or refractory to first-line treatments
  • Patient requests specialist opinion 2

By following this structured approach to diagnosis and treatment, clinicians can effectively manage IBS, improve patient quality of life, and avoid unnecessary investigations and treatments that may increase healthcare costs without improving outcomes.