Irritable bowel syndrome

Background

• Syndrome characterized by abdominal pain or discomfort and altered bowel movements
• May be diarrhea- or constipation-predominant, or mixed

Etiology

• Post-infectious IBS
• Idiopathic

Epidemiology

• Prevalence of 10-15% in North America

Differential Diagnosis

• Celiac disease
• Inflammatory bowel disease (IBD)
• Microscopic colitis, especially in older patients
• Overflow diarrhea, especially in older patients
• Others
  • Chronic infection (e.g. Giardia, Entamboeba)

Investigations

• Labs
  • Celiac disease
    • Anti-TTG +/- IgA levels
    • HLA DQ2/DQ8, when already on gluten-free diet
  • IBD
    • ESR/CRP
    • Fecal calprotectin
• Imaging
  • AXR, to rule out overflow diarrhea
• Other
  • Colonoscopy, if over 50 years old or alarm features, to rule out microscopic colitis and IBD

Diagnosis

• Made based on Rome Diagnostic Criteria and the exclusion of other causes of their symptoms

Rome Diagnostic Criteria

• Recurrent abdominal pain for >= 3 days per month for >= 3 months
• Two of the following:
  • Symptoms improve with bowel movements
  • Associated with a change in stool frequency
  • Associated with a change in stool consistency

Management

• Provide reassurance and education
• Lifestyle modification
  • Small, frequent meals
  • Avoid fatty foods
  • Increased physical activity
  • May try:
    • Lactose avoidance
    • Gluten- or FODMAPS-free diet
    • Dietary fibre may help or harm
  • If bloating: avoid beans/dried fruit/bananas
• Medical therapy
  • Mild IBS
    • Antispasmodics (butylscopolamine (Buscopan), scheduled or prn)
    • Anti-diarrheals (Immodium prn) for diarrhea-predominant
    • Probiotics (Align and Tuzen)
  • Moderate or severe IBS
    • Tricyclic antidepressants (6-8 weeks to take effect)
    • SSRIs if concurrent depression
    • CBT and hypnotherapy
    • Rifaximin
    • Linaclutide (Constella) for consipation-predominant