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  4. Irritable Bowel Syndrome (IBS)

Irritable Bowel Syndrome (IBS)

NICE Clinical guideline [CG61] Irritable bowel syndrome in adults: diagnosis and management. Last updated: Apr 2017. NICE CKS Irritable bowel syndrome. Last revised: Aug 2023.

Guidelines

IBS can be diagnosed clinically, there are no objective tests. The following features are extracted from NICE's diagnostic criteria, see below for the full diagnostic criteria.
  • Core features of IBS:
    • Abdominal pain or discomfort that is worsened by eating and relieved by defecation
    • Bloating / distension / tension
    • Change in bowel habit (bowel frequency or stool form) + passage of mucus
 
  • Other supportive features:
    • Lethargy
    • Nausea
    • Backache
    • Bladder symptoms

 

Ensure to exclude and further investigate the following, if IBS is suspected:

  • Inflammatory bowel disease
  • GI tract cancer

  • Abdominal pain / discomfort relieved by defaecation or associated with altered bowel frequency or stool form, and
  • At least 2 of the following
    • Altered stool passage (straining, urgency, incomplete evacuation)
    • Abdominal bloating (more common in women than men), distension, tension or hardness
    • Symptoms made worse by eating
    • Passage of mucus

Other features such as lethargy, nausea, backache and bladder symptoms are common in people with IBS, and may be used to support the diagnosis

Note that NICE CKS states that ROME IV Criteria for IBS are often used in secondary care (which is very similar to those recommended by NICE).

The following tests should be performed routinely in those who meet the IBS clinical diagnostic criteria:
  • FBC
  • ESR and CRP
  • Coeliac serology
  • Faecal calprotectin - esp. in those ≤45 y/o (advised by NICE CKS, to exclude inflammatory bowel disease)

Advise the following:
  • Regular meals and take time to eat (avoid missing meals or leaving long gaps between meals)
  • At least 8 cups of fluid per day (esp. water or non-caffeinated drinks)
  • Oats and linseeds may be helpful for wind and bloating
    • These are soluble fibres, insoluble fibres should be discouraged
 
  • 2nd line: consider exclusion diets - e.g. FODMAPFermentable oligosaccharides, disaccharides, monosaccharides and polyols diet (only to be started by those with expertise in dietary management)

The following should be AVOIDED or RESTRICTED (as they may worsen symptoms):
  • Tea and coffee (to max 3 cups per day)
  • Alcohol and fizzy drinks
  • High-fibre food (insoluble fibres, e.g. wholemeal or high‑fibre flour and breads, cereals high in bran, and whole grains such as brown rice)
  • Fresh fruit (to max 3 portions per day)
  • Sorbitol (an artificial sweetener) - avoid in those who experience diarrhoea
  • Resistant starch (often found in processed or re-cooked foods)

Management depends on the predominant symptom:
 
Predominant symptom Treatment
Constipation
  • 1st line: bulk-forming laxative
  • 2nd line: other classes of laxative (but avoid lactulose)
  • 3rd line: linaclotide
Diarrhoea
  • Loperamide (anti-motility drug)
Abdominal pain / spasm
  • 1st line: PRN antispasmodic drugs
    • Meveverine hydrochloride
    • Alverine citrate
    • Peppermint oil
 
  • 2nd line: low-dose TCATricyclic anti-depressant (e.g. amitriptyline)
 

References

Author: Adams Lau
Reviewer:
Last edited: 11/08/25