IBS.

Irritable bowel syndrome (IBS) is a very common functional bowel disorder causing chronic abdominal pain and altered bowel habits.
It is benign but often distressing, and frequently leads to repeated healthcare visits and unnecessary investigations.

This guide focuses on how to diagnose IBS safely, exclude red flags, and manage patients practically in NHS practice.

What is IBS?

IBS is:

A functional gut disorder with no structural or inflammatory cause.

In simple terms:

  • The bowel looks normal
  • Tests are normal
  • But symptoms are real

It is not “in the patient’s head”, but also not inflammatory or malignant.

How does it present?

Typical symptoms:

  • Recurrent abdominal pain
  • Bloating
  • Diarrhoea, constipation, or both
  • Urgency
  • Mucus in stool
  • Symptoms relieved after opening bowels

Often fluctuates:

  • Good days and bad days
  • Triggered by stress or certain foods

Symptoms usually present for months or years, not days.

IBS subtypes (practical classification)

  • IBS-D → diarrhoea predominant
  • IBS-C → constipation predominant
  • IBS-M → mixed
  • IBS-U → unclear

Helps guide treatment choice.

On the ward or clinic, always ask

Are there any red flags?

Because:

IBS is a diagnosis of inclusion with red flags excluded.

Never label IBS without checking for warning signs.

Red flags you must actively exclude

If any of these are present → do not diagnose IBS:

  • Weight loss
  • GI bleeding
  • Iron deficiency anaemia
  • Nocturnal symptoms
  • Fever
  • Family history of bowel cancer/IBD
  • Onset age >50
  • Persistently raised CRP
  • Severe systemic illness

These suggest:

  • Cancer
  • IBD
  • Coeliac disease
  • Infection

Not IBS.

Initial assessment (what juniors should actually do)

For typical chronic symptoms:

Do basic tests:

  • FBC
  • CRP
  • Coeliac screen (tTG)
  • Stool calprotectin (if diarrhoea predominant)
  • Consider thyroid function

Usually:
Normal results + no red flags = IBS likely

You do not need CT scans or colonoscopy for everyone.

First priority = reassure safely

Most patients are worried about:

  • Cancer
  • “Something serious”

Clear explanation is often the most effective treatment.

Explain:

  • Tests are normal
  • No inflammation
  • Common condition
  • Manageable

Reassurance reduces symptoms significantly.

Management (real-world practical approach)

Treatment is symptom-based.

General advice (for everyone)

  • Regular meals
  • Adequate fluids
  • Exercise
  • Stress management
  • Reduce caffeine
  • Trial low FODMAP diet

Diet is often more effective than medication.

IBS-D

  • Loperamide
  • Low FODMAP diet
  • Consider bile acid malabsorption if persistent

IBS-C

  • Fibre (gradual)
  • Laxatives (e.g. macrogol)
  • Hydration

Pain/bloating

  • Antispasmodics (mebeverine, hyoscine)
  • Peppermint oil
  • Low-dose amitriptyline if chronic

When to refer to gastro

Refer if:

  • Red flags
  • Abnormal bloods
  • Uncertain diagnosis
  • Persistent severe symptoms
  • Failure of first-line measures

Do not refer every mild IBS case.

Common mistakes juniors make

  • Diagnosing IBS without basic tests
  • Missing coeliac disease
  • Missing IBD
  • Over-investigating low-risk patients
  • Not reassuring properly
  • Using scans unnecessarily

Remember:
Too many tests can increase anxiety rather than help.

Take-home concept

IBS is common and benign.
Your job is to exclude red flags, avoid unnecessary investigations, reassure confidently, and treat symptoms practically.