Irritable Bowel Syndrome

Functional GI disorder; recurrent abdominal pain with altered bowel habit, no structural/biochemical abnormality.

Rome IV: pain ≥1 day/week × 3 months, ≥2 of (related to defecation, change in stool frequency, change in stool form).

Classified: IBS-C, IBS-D, IBS-M, IBS-U.

• Abdominal pain/cramping (relieved by defecation), bloating, altered bowel habit, mucus in stool, incomplete evacuation sensation, stress/food-triggered exacerbation.

• Extraintestinal: fatigue, fibromyalgia, migraine, anxiety/depression.

Red flags: rectal bleeding, weight loss, nocturnal symptoms, onset age >50, family history colorectal cancer/IBD/celiac, iron-deficiency anemia, palpable mass, fever.

• Clinical (Rome IV) positive diagnosis, not exclusion-only.

• Limited targeted workup: FBC, fecal calprotectin (excludes IBD), celiac serology, TSH if indicated, stool studies if relevant exposure.

• Colonoscopy: not routine without red flags/age <50.

Differentials: IBD, celiac disease, colorectal malignancy, microscopic colitis, lactose intolerance, SIBO, bile acid diarrhea, endometriosis.

• Education: reassure functional but genuine (gut-brain axis dysfunction, visceral hypersensitivity), chronic relapsing course

• Dietary: regular meals, adequate fluid, trial low FODMAP diet under dietitian guidance; adequate soluble fiber for IBS-C

• IBS-C: osmotic laxatives (macrogol) first-line; linaclotide/lubiprostone for refractory pain+constipation

• IBS-D: loperamide prn; colestyramine if bile acid diarrhea suspected; low-dose rifaximin for refractory IBS-D

• Antispasmodics: mebeverine, hyoscine butylbromide, peppermint oil; pre-meal

• Low-dose amitriptyline 10-25mg nocte: effective for pain-predominant IBS, particularly IBS-D

• SSRIs: alternative, particularly IBS-C or comorbid anxiety/depression

• Psychological therapies (CBT, gut-directed hypnotherapy): good evidence for refractory symptoms

• Probiotics: some evidence, strain-specific, low-risk trial

Referral: gastroenterology for red flags/diagnostic uncertainty/refractory disease; dietitian for low FODMAP; psychology for gut-directed hypnotherapy.