Irritable Bowel Syndrome

Catie Gray

Background

  • A disorder of gut-brain interaction.
  • Diagnosed by the Rome IV criteria, no longer a diagnosis of exclusion. 
    • Recurrent abdominal pain on average at least 1 day/week in the last 3 months with an onset at least 6 months prior, associated with two or more of the following criteria.
    • Pain related to defecation.
    • Change in frequency of stool.
    • Change in form (appearance) of stool.
    • Alarm features requiring further evaluation: >50yrs, evidence of GIB, nocturnal pain or BMs, unintentional weight loss, family hx of colorectal cancer or IBD, palpable abdominal mass or LAD, IDA, +FOBT.
    • Classified based on predominant bowel habits.
    • IBS-D (Diarrhea): >25% BMs with Bristol stool types 6 or 7.
    • IBS-C (Constipation): >25% BMs with Bristol stool types 1 or 2.
    • IBS-M (Mixed): both of above.

Evaluation

  • Evaluate for alarm symptoms above.
  • Consider limited testing with CBC, CMP, CRP, celiac serology (TTG, anti-gliadin, etc), fecal calprotectin.

Management

  • (1) Lifestyle/Dietary Modifications: 
    • Increased physical activity, low FODMAP diet (I: Eliminate high FODMAP foods for 4-6 wks, II: Incorporate foods back into diet and see what’s tolerable, recommend under guidance of dietitian).
    • No evidence for probiotics (can potentially worsen bloating 2/2 SIBO).
  • (2) Psychosocial Treatment: 
    • o CBT, gut-directed hypnotherapy, psychotherapy, therapeutic physician-patient relationship.
  • (3) Pharmacologic Treatment: 
    • Pain: colicky abdominal pain, avoid opioids.
    • Peppermint oil (smooth muscle relaxant) – IBGuard, Iberogast.
    • Antispasmodics (not strongly recommended): Hyoscyamine (0.125 - 0.25 mg q4h prn with a max of 1.5mg/day) acts faster than Dicyclomine (20 mg q6h prn up to 40 mg q6h prn).
    • TCAs (slow GI transit): Amitriptyline or nortriptyline (causes less constipation so better in IBS-C). Note: both TCAs and antispasmodics can slow GI transit.
    • Diarrhea: 
    • Ondansetron (8mg TID), Loperamide (up to 16g qd), Rifaximin (550mg BID for 2 wks), Eluxadoline (75-100mg BID, contraindicated if s/p cholecystectomy) and alosetron; consider Lomotil if refractory.
    • Constipation: 
    • Fiber (Ispaghula husk orange), Miralax, Linzess (first line), Trulance, or Amitiza; TCAs also efficacious. 
    • Other: 
    • SSRIs, SNRIs for concomitant mood disorders.
    • Gabapentin, Lyrica (not formally recommended).
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