Irritable Bowel Syndrome
A functional bowel disorder causing abdominal pain with altered bowel habit.
Overview
IBS is diagnosed clinically (Rome IV criteria) once red flags are excluded. Pain is relieved by defecation and associated with change in stool frequency or form. Management combines diet (low-FODMAP trial), stress care and targeted medication.
Symptoms
- • Abdominal cramping
- • Bloating
- • Diarrhoea, constipation, or both
- • Mucus in stool
- • Symptoms relieved by passing stool
Risk factors
- • Female sex
- • Age <50
- • Previous gastroenteritis
- • Stress and anxiety
- • Family history
Causes
- • Gut-brain axis dysregulation
- • Visceral hypersensitivity
- • Post-infective changes
- • Altered microbiome
🚨 Red flags — seek urgent care
- • Rectal bleeding
- • Weight loss
- • Nocturnal diarrhoea
- • Family history of bowel cancer or IBD
- • Onset >50
When to seek care
- • New symptoms after 50
- • Any red flag
- • Symptoms disrupting daily life
Diagnosis
- • Rome IV criteria: recurrent abdominal pain ≥1 day/week for 3 months associated with defecation, change in stool frequency, or change in stool form
- • Limited investigation: FBC, CRP, coeliac serology, faecal calprotectin to exclude IBD
- • Subtype: IBS-C (constipation), IBS-D (diarrhoea), IBS-M (mixed), IBS-U (unspecified)
- • Red flag review — refer for endoscopy if alarm features
Treatment
- • First-line: dietary modification (regular meals, limit caffeine/alcohol, low-FODMAP trial with dietitian)
- • Antispasmodic (mebeverine, peppermint oil) for pain
- • Laxative (osmotic) for IBS-C; loperamide for IBS-D
- • Low-dose TCA (amitriptyline) or SSRI for refractory pain
- • Psychological therapy (CBT, gut-directed hypnotherapy) for persistent symptoms
Prevention
- • Regular meal pattern and hydration
- • Identify and limit individual food triggers
- • Stress management, sleep hygiene
- • Regular physical activity
Complications
- • Reduced quality of life and work absenteeism
- • Anxiety, depression, somatisation
- • Pelvic floor dysfunction
- • Unnecessary investigations and treatments
Education & self-care
This guidance is reviewed by Dr. Handel Emery, MD, FRCP (UK) and last updated 2026-06-08. It is educational and not a substitute for professional medical advice.
Frequently asked questions
Is a low-FODMAP diet helpful?
Yes — a structured trial under a dietitian helps around 70% of patients. It is not intended as a long-term diet.
What is the low-FODMAP diet?
A short-term elimination diet that restricts fermentable carbohydrates which can trigger IBS symptoms. It works for about 70% of people and is best delivered with a registered dietitian.
Are probiotics worth trying?
Some strains (especially Bifidobacterium infantis 35624) modestly improve symptoms. Try a single product for at least 4 weeks before deciding.
When is colonoscopy needed?
If there are red flags — unintentional weight loss, rectal bleeding, iron-deficiency anaemia, onset over age 50, nocturnal diarrhoea or a strong family history of bowel cancer or IBD.