Irritable Bowel Syndrome and Chronic Constipation

Irritable Bowel Syndrome definition

Syndrome of GI sensory + motor dysfunction; diagnosis of exclusion.

Rome IV criteria for IBS

Recurrent abdominal pain ≥1 day/week for 3 months + 2 of: related to defecation, altered stool frequency, altered stool form.

IBS pathophysiology

Visceral hypersensitivity + dysregulated motility + brain–gut axis dysfunction + microbiome + psychosocial factors.

IBS pain features

Crampy, hypogastric/paraumbilical, post‑prandial, NOT nocturnal, relieved by defecation.

IBS associated symptoms

Bloating, distention, gas, incomplete evacuation.

IBS red flags (meaning it isn’t IBS)

Blood in stool, iron deficiency anemia, nocturnal symptoms, weight loss, fever, recent onset in older adults.

IBS associated conditions

Migraine, fibromyalgia, anxiety/panic disorders, POTS.

IBS‑D vs non‑IBS diarrhea onset

IBS‑D: long‑standing; non‑IBS: recent/sudden.

IBS‑D daily pattern vs Non-IBS

IBS: Unpredictable. Non IBS: Certain meals

IBS vs Non‑IBS food triggers

None for IBS; Non IBS: Dairy, fruit, meat.

IBS‑D stress effect vs Non IBS

Worsens symptoms. Non IBS: no impact

Conditions mimicking IBS‑D

Post‑infectious IBS, SIBO, lactose intolerance, fructose malabsorption, bile acid malabsorption, early celiac/IBD, alpha‑gal syndrome(tick bite now allergic to meat).

Dietary therapy for IBS

Reassurance, avoid carbonated/spicy/fatty foods, avoid sugar alcohols, lactose/fructose restriction, increase fiber, low‑FODMAP diet, probiotics.

IBS‑D drug: antispasmodics

Dicyclomine, hyoscyamine; M1 antagonists; ↓ SM tone, dec GI motility; SE: dry mouth, blurry vision, urinary retention.

IBS‑D drug: peppermint oil (L-menthol)

K‑opioid/5‑HT3 antagonist; antispasmotic SE: GERD, reflux, nausea.

IBS‑D drug: loperamide(Imodium)

μ‑opioid agonist; slows transit; antidiarrheal SE: constipation.

IBS‑D drug: rifaximin

Non‑absorbable antibiotic; alters microbiome; few SE. (Min like minimum like micro like microbiome antibiotic)

IBS‑D drug: amitriptyline

↓ visceral pain, ↓ motility; SE: constipation, dry mouth, sedation.

Primary constipation types

IBS‑C, normal transit, slow transit (colonic inertia), pelvic floor dysfunction.

Secondary constipation causes

Low fiber, dehydration, opioids, anticholinergics, CCBs, iron, pregnancy, hypothyroid, diabetes, hypercalcemia, Parkinson’s, MS, stroke, malignancy.

Constipation OTC: osmotic agents

Polyethylene glycol (best evidence), lactulose, Mg citrate/hydroxide; Thet increase intraluminal water retention softening stool SE: bloating, diarrhea.

Constipation OTC: stimulant agents

Senna, bisacodyl; ↑ ENS activity + colonic motor movement; SE: cramping; long‑term use may damage ENS.

Constipation Rx: lubiprostone

CIC‑2 activator → ↑ Cl⁻ + water secretion; SE: nausea, diarrhea.

Constipation Rx: linaclotide

GC‑C agonists → ↑ cGMP → activate CFTR, ↑ Cl⁻ + water secretion; SE: diarrhea, dizziness. (A touch of cholera!)

Polyethylene glycol

Treats constripation; non absorbable high molecular weight polymer; increases colonic intraluminal water retention to soften stool; AE: bloating, nausea, diarrhea, gassiness

Senna or Bisacodyl

Treats constipation; ENS stimulant that increases smooth muscle tone and colonic motility; AE: cramping, long term use can damage ENS

IBS summary

Chronic abdominal pain + altered bowel habits without red flags; diagnosis of exclusion.

CIC summary

Chronic constipation due to motility or pelvic floor dysfunction; treated with diet, meds, biofeedback.