Irritable Bowel Syndrome

IBS Basics - Gut Feeling Gone Wrong

• Chronic functional GI disorder: Recurrent abdominal pain, altered bowel habits (diarrhea, constipation, or mixed). No organic pathology.
• Pathophysiology: Gut-brain axis dysfunction, visceral hypersensitivity, altered motility, gut microbiota dysbiosis, low-grade inflammation.
• Risk Factors: Genetics, stress, prior gastroenteritis (Post-Infectious IBS or PI-IBS), food intolerances.
• Epidemiology: Affects ~10-15% of population; Female > Male.

⭐ Post-infectious IBS (PI-IBS) can develop in up to 20% of individuals after an episode of acute gastroenteritis.

• Diagnosis of exclusion, based on symptom criteria (e.g., Rome IV).

Why Me? - IBS Inner Workings

• Gut-Brain Axis Dysregulation: Core issue; bidirectional CNS-ENS miscommunication.
  • Psychological factors (stress, anxiety) significantly influence symptoms.
  • Serotonin (5-HT) signaling alterations impact motility and sensation.
• Altered Gut Motility:
  • IBS-D: Accelerated colonic transit.
  • IBS-C: Delayed colonic transit.
• Visceral Hypersensitivity: Heightened pain perception from normal gut stimuli.
  • Nerve endings in gut wall are oversensitive.
• Gut Microbiota Imbalance (Dysbiosis):
  • Altered bacterial composition; Small Intestinal Bacterial Overgrowth (SIBO) link.
• Low-Grade Inflammation & Immune Activation:
  • Subtle inflammation, ↑ mast cells, ↑ intestinal permeability ("leaky gut").

⭐ Post-infectious IBS (PI-IBS) develops in a subset of patients (approx. 10-20%) following an episode of acute bacterial gastroenteritis.

Spotting IBS - Symptom Sleuthing

• Core: Recurrent abdominal pain, altered bowel habits (diarrhea/constipation/mixed).
• Rome IV Criteria (symptom onset ≥6 mo prior; active for last 3 mo):
  • Recurrent abd. pain (≥1 day/wk)
  • Associated with ≥2 of:
    • Pain linked to defecation
    • Stool frequency change
    • Stool form change (Bristol)
• Subtypes (Bristol):
  • IBS-C: >25% hard, <25% loose stools
  • IBS-D: >25% loose, <25% hard stools
  • IBS-M: >25% hard & >25% loose
  • IBS-U: Unsubtyped
• ⚠️ Alarm Features (Red Flags):
  • Onset >50 yrs, weight loss, nocturnal sx
  • Rectal bleeding, Fe def. anemia
  • Fam Hx: IBD, celiac, CRC

⭐ Rome IV: Key for diagnosis; positive criteria, not just exclusion.

Not Just IBS - Ruling Rivals Out

• Key: Exclude organic pathology. Watch for alarm features:
  • Weight loss, rectal bleeding, anemia
  • Nocturnal symptoms, family Hx (CRC/IBD), age >50
• IBD (Crohn's/UC): Endoscopy, biopsy.
• Celiac Disease: Serology (anti-tTG), biopsy.
• Infections (India): Amoebiasis, Giardiasis. Stool tests.
• Lactose Intolerance: H2 breath test.
• Colorectal Cancer: Colonoscopy if alarm signs.
• Microscopic Colitis: Biopsy essential.

⭐ Nocturnal diarrhea is a key red flag pointing away from IBS towards organic causes like IBD or microscopic colitis.

Taming the Tumult - IBS Treatment Toolkit

• Foundation: Reassurance, education, regular physical activity.
• Dietary: Low FODMAP diet trial (key for bloating/pain).
• Pharmacotherapy (Subtype-Guided):
  • IBS-C: Soluble fiber (psyllium), PEG; Lubiprostone, Linaclotide if needed.
  • IBS-D: Loperamide (acute); Rifaximin (550mg TID x 14d); Eluxadoline. Alosetron (severe, ♀, REMS).
  • Abdominal Pain: Antispasmodics (Dicyclomine), Peppermint oil. Low-dose TCAs (Amitriptyline 10-25mg).
• Psychological: CBT, hypnotherapy, stress management.

⭐ Rifaximin, a gut-selective antibiotic, offers durable relief of bloating and abdominal pain in non-constipated IBS (IBS-D/M).

High‑Yield Points - ⚡ Biggest Takeaways

• Rome IV criteria for diagnosis: recurrent abdominal pain related to defecation, or change in stool frequency/form.
• Subtypes: IBS-C (constipation-predominant), IBS-D (diarrhea-predominant), IBS-M (mixed).
• A functional bowel disorder; diagnosis of exclusion. Rule out organic disease.
• Red flag symptoms (weight loss, bleeding, anemia) necessitate further investigation.
• Management: low FODMAP diet, lifestyle changes, antispasmodics, loperamide, laxatives.
• Pathophysiology involves visceral hypersensitivity, altered gut motility, and gut-brain axis dysfunction.
• Often associated with psychological distress (anxiety, depression).