Irritable Bowel Syndrome in Adults: NICE Guideline CG61 Summary

Definition & Key Features

What is Irritable Bowel Syndrome (IBS)? IBS is a chronic, relapsing, and often lifelong functional gastrointestinal disorder. It is characterised by the presence of abdominal pain or discomfort, which may be associated with defaecation and/or accompanied by a change in bowel habit.

Core Pathophysiology: While not fully elucidated, it’s considered a disorder of gut-brain interaction, involving visceral hypersensitivity, altered gut motility, and potentially low-grade inflammation or post-infectious changes.
Hallmark Features:
- Abdominal pain or discomfort.
- Altered bowel habit (diarrhoea, constipation, or alternating).
- Bloating or abdominal distension.
Typical Signs/Symptoms:
- Abdominal pain/discomfort relieved by defaecation or associated with altered bowel frequency/stool form.
- Altered stool passage (straining, urgency, incomplete evacuation).
- Abdominal bloating (more common in women), distension, tension, or hardness.
- Symptoms made worse by eating.
- Passage of mucus.
- Other common associated symptoms: lethargy, nausea, backache, bladder symptoms.
Important Complications or Side Effects if Untreated: IBS itself does not lead to serious organic disease like cancer or inflammatory bowel disease. However, untreated or poorly managed symptoms can significantly impair quality of life, lead to psychological distress (anxiety, depression), unnecessary investigations, and work absenteeism.

Epidemiology & Risk Factors

Who is most affected?
- Prevalence: Estimated between 10% and 20% in the general population.
- Age Patterns: Most often affects people between 20 and 30 years. There is also a significant prevalence in older people, and IBS should be considered in older individuals presenting with unexplained abdominal symptoms.
- Gender Patterns: Twice as common in women as in men.
Modifiable Risk Factors: While not explicitly detailed as “risk factors” in the provided guideline text, factors like diet, stress, and possibly previous gastrointestinal infections can influence symptom expression.
Non-Modifiable Risk Factors: Female gender, younger age (though can occur at any age).

Clinical Presentation & Diagnosis

Typical Symptoms: As listed under “Hallmark Features” and “Typical Signs/Symptoms” above. Symptom profiles vary, commonly “diarrhoea predominant,” “constipation predominant,” or “alternating.” Clinicians should use the Bristol Stool Form Scale to help patients describe stool consistency. Ask open questions about symptom impact on daily life, including potential faecal incontinence (disclosed by ~20% only if asked).
Red Flags (Indications for urgent referral or action): All people presenting with possible IBS symptoms should be assessed and clinically examined for the following ‘red flag’ indicators and should be referred to secondary care for further investigation if any are present:
- Evidence of signs and symptoms of cancer (in line with NICE guideline on suspected cancer: recognition and referral). This includes (but is not limited to):
  - Unintentional and unexplained weight loss.
  - Rectal bleeding.
  - A family history of bowel or ovarian cancer.
  - A change in bowel habit to looser and/or more frequent stools persisting for more than 6 weeks in a person aged over 60 years.
  - Anaemia.
  - Abdominal masses.
  - Rectal masses.
- Presence of inflammatory markers for inflammatory bowel disease (IBD).
Diagnostic Criteria: Consider assessment for IBS if a person reports having had any of the following for at least 6 months:

Abdominal pain or discomfort
Bloating
Change in bowel habit

A diagnosis of IBS should be considered only if the person has abdominal pain or discomfort that is either:

Relieved by defaecation, OR
Associated with altered bowel frequency or stool form. AND this should be accompanied by at least 2 of the following 4 symptoms:

Altered stool passage (straining, urgency, incomplete evacuation).
Abdominal bloating (more common in women), distension, tension, or hardness.
Symptoms made worse by eating.
Passage of mucus.

Differential Diagnoses: Coeliac disease, inflammatory bowel disease, bowel cancer, gynaecological conditions (e.g., endometriosis, ovarian cancer), thyroid dysfunction, lactose intolerance, infective gastroenteritis.
Investigations (Timing and Rationale): In people who meet the IBS diagnostic criteria, undertake the following to exclude other diagnoses:
- Full blood count (FBC)
- Erythrocyte sedimentation rate (ESR) or plasma viscosity
- C-reactive protein (CRP)
- Antibody testing for coeliac disease (tissue transglutaminase [TTG] or endomysial antibodies [EMA]).

The following tests are NOT necessary to confirm diagnosis in people who meet IBS diagnostic criteria (unless red flags are present or clinical suspicion for an alternative diagnosis is high):

Ultrasound
Rigid/flexible sigmoidoscopy
Colonoscopy; barium enema
Thyroid function test
Faecal ova and parasite test
Faecal occult blood
Hydrogen breath test (for lactose intolerance and bacterial overgrowth)

Initial Management

Non-Pharmacological Measures & Patient Education:
- Explain the importance of self-help: general lifestyle, physical activity, diet, symptom-targeted medication.
- Encourage relaxation time and leisure activities.
- Assess physical activity levels (e.g., GPPAQ); advise increased activity if low.
- General Dietary Advice:
  - Have regular meals and take time to eat.
  - Avoid missing meals or long gaps between eating.
  - Drink at least 8 cups of fluid per day (especially water or non-caffeinated drinks).
  - Restrict tea and coffee to 3 cups per day.
  - Reduce intake of alcohol and fizzy drinks.
  - Consider limiting high-fibre food (e.g., wholemeal bread, high-bran cereals).
  - Reduce intake of ‘resistant starch’ (often in processed/re-cooked foods).
  - Limit fresh fruit to 3 portions per day (approx. 80g per portion).
  - For diarrhoea: Avoid sorbitol (artificial sweetener).
  - For wind and bloating: Consider oats (e.g., porridge) and linseeds (up to 1 tablespoon per day).
- Fibre Intake: Review and adjust (usually reduce) insoluble fibre (e.g., bran). If fibre increase is advised, use soluble fibre (e.g., ispaghula powder, oats).
- Probiotics: If chosen, take for at least 4 weeks at manufacturer’s recommended dose, monitoring effect.
- Aloe Vera: Discourage use.
First-line Pharmacological Treatment (symptom-dependent):
- Antispasmodics (for pain):
  - Drug examples: Mebeverine, Alverine citrate, Hyoscine butylbromide, Peppermint oil capsules.
  - Dosage/Formulation/Route/Frequency: As per individual product SmPC; generally taken “as required.”
  - Indications: Abdominal pain or spasms.
  - Duration: Use as needed.
  - Major Side Effects: Generally well-tolerated; refer to individual SmPCs (e.g., dry mouth, blurred vision with hyoscine).
  - Contraindications/Cautions: Refer to individual SmPCs (e.g., paralytic ileus for hyoscine, caution in glaucoma).
- Laxatives (for constipation):
  - Drug examples: Macrogols (e.g., Movicol, Laxido) are often preferred. Avoid lactulose (can cause bloating). Stimulant laxatives (e.g., senna, bisacodyl) can be used short-term if macrogols are insufficient.
  - Dosage/Formulation/Route/Frequency: Titrate dose according to stool consistency, aiming for a soft, well-formed stool (Bristol Stool Form Scale type 4).
  - Indications: Constipation-predominant IBS.
  - Duration: Adjust according to response.
  - Major Side Effects: Abdominal cramps, bloating, diarrhoea if dose too high.
  - Contraindications/Cautions: Intestinal obstruction, faecal impaction.
- Antimotility Agents (for diarrhoea):
  - Drug name: Loperamide (first choice).
  - Dosage/Formulation/Route/Frequency: Start with 2mg as needed after loose stools, up to a maximum dose as per SmPC (typically 16mg/day). Titrate dose according to stool consistency, aiming for Bristol Stool Form Scale type 4.
  - Indications: Diarrhoea-predominant IBS.
  - Duration: Adjust according to response.
  - Major Side Effects: Constipation, dizziness, abdominal cramps.
  - Contraindications/Cautions: Conditions where inhibition of peristalsis is to be avoided (e.g., acute dysentery, ulcerative colitis flare).
Initial Monitoring Parameters: Review patient symptoms, stool consistency (using Bristol Stool Form Scale), and medication tolerability within a few weeks of starting any new treatment or dietary change.

Further Management & Escalation

Second-Line Therapies (if first-line fails or is contraindicated):
- Tricyclic Antidepressants (TCAs):
  - Indication: For abdominal pain/discomfort if laxatives, loperamide, or antispasmodics have not helped.
  - Drug example: Amitriptyline.
  - Dosage/Route/Frequency: Start at a low dose (e.g., 5-10 mg equivalent of amitriptyline) once at night. Review regularly. Increase dose if needed, but not usually beyond 30 mg.
  - Duration: Ongoing if effective, review regularly.
  - Key Considerations: Off-label use. Prescriber takes full responsibility. Obtain and document informed consent.
  - Side Effects: Drowsiness, dry mouth, constipation, blurred vision.
  - Cautions: Elderly, cardiac disease, glaucoma, urinary retention.
- Selective Serotonin Reuptake Inhibitors (SSRIs):
  - Indication: Consider only if TCAs are ineffective.
  - Key Considerations: Off-label use. Prescriber takes full responsibility. Obtain and document informed consent.
  - Follow-up for TCAs/SSRIs: Review after 4 weeks, then every 6-12 months.
Specialist Interventions:
- Dietary Management (Specialist): If symptoms persist despite general advice, offer referral to a healthcare professional with expertise in dietary management for:
  - Single food avoidance.
  - Exclusion diets (e.g., low FODMAP diet).
- Linaclotide (for constipation):
  - Indication: Only if optimal or maximum tolerated doses of previous laxatives from different classes have not helped AND they have had constipation for at least 12 months.
  - Follow-up: Review after 3 months.
- Psychological Interventions:
  - Referral Criteria: Consider for people with IBS who do not respond to pharmacological treatments after 12 months and who develop a continuing symptom profile (refractory IBS).
  - Interventions: Cognitive Behavioural Therapy (CBT), hypnotherapy, and/or psychological therapy.
Referral Criteria (General):
- Presence of any red flag symptoms (urgent).
- Diagnostic uncertainty.
- Need for specialist dietary management (e.g., low FODMAP).
- Refractory IBS (symptoms persist after 12 months of pharmacological treatments) for consideration of psychological interventions.
Red Flags for Urgent Escalation: Reiterate all red flags listed in the “Clinical Presentation & Diagnosis” section. Any new emergence of these during management warrants urgent reassessment and potential referral.
Surgical Options: Not applicable for IBS.

Follow-up & Safety Netting

Frequency of Follow-up Visits:
- Agreed between healthcare professional and patient, based on symptom response.
- Part of an annual patient review.
- Specific follow-up for TCAs/SSRIs: After 4 weeks of starting, then every 6-12 months.
- Specific follow-up for Linaclotide: After 3 months.
Monitoring Requirements: Symptom diary, Bristol Stool Form Scale, medication adherence and side effects, impact on quality of life. Reassess for red flags at each review.
Patient Advice on Self-Management: Reinforce the importance of lifestyle adjustments, dietary strategies, regular physical activity, stress management, and appropriate use of prescribed/OTC medications. Provide information on patient support groups.
Health Promotion: General advice on healthy living. Specific vaccinations are not highlighted for IBS but should follow general population guidelines.
Warning Signs Prompting Urgent Reassessment:
- Any new ‘red flag’ symptom (e.g., unintentional weight loss, rectal bleeding, persistent change in bowel habit especially if >60 years, family history of bowel/ovarian cancer, anaemia, abdominal/rectal mass).
- Significant worsening of symptoms despite adherence to management plan.
- Development of severe or intolerable side effects from medication.

Key Points to Remember

Diagnosis: IBS is a positive clinical diagnosis based on symptom criteria (abdominal pain related to defecation/bowel changes + at least 2 other features like altered stool passage, bloating, symptoms worse with eating, mucus) present for at least 6 months.
Red Flags First: Always assess for and act on red flags (e.g., weight loss, rectal bleeding, new persistent change in bowel habit >60yrs) by referring to secondary care.
Essential Blood Tests: Perform FBC, ESR/CRP, and coeliac serology (TTG/EMA) in all suspected IBS to exclude other conditions.
Stepwise Management: Start with lifestyle/dietary advice. Symptomatic treatment includes antispasmodics (pain), loperamide (diarrhoea – first choice), and laxatives (constipation – avoid lactulose, titrate to stool type 4).
Second-Line Pharmacological: Low-dose TCAs (e.g., amitriptyline 5-30mg nocte) for pain if initial measures fail. SSRIs if TCAs ineffective. Both are off-label; ensure informed consent and specific follow-up.
Specialist Referral: Consider for refractory symptoms, specialist dietary input (e.g., low FODMAP), or psychological therapies (CBT, hypnotherapy if no response after 12 months of meds).
Dietary Nuances: Reduce insoluble fibre (bran); encourage soluble fibre (ispaghula, oats) if fibre is needed. Probiotics can be trialled for at least 4 weeks.
Patient Education is Key: Empower patients with self-management strategies.
Follow-up: Regular review is important, including an annual review. Urgently reassess if red flags emerge.
Linaclotide: Consider for persistent constipation (>=12 months) unresponsive to other laxatives; review after 3 months.

Take-Home Points

Diagnose Positively: Use NICE criteria (symptoms ≥6 months, pain + 2 other features).
Rule Out Red Flags & Coeliac Disease: Blood tests (FBC, CRP/ESR, TTG/EMA) are mandatory.
Manage Stepwise: Lifestyle/Diet ➔ Symptomatic Meds (Antispasmodics, Loperamide, Laxatives) ➔ Low-Dose TCAs/SSRIs (off-label) ➔ Specialist Diet/Psychology.
Safety Net: Always ask about red flags at diagnosis and follow-up. Urgent referral if present.
Educate & Empower: Self-management is crucial for this chronic condition.

This MedDigest summary is intended for educational purposes only and should not be used for clinical purposes. It is an independent resource, prepared by MedDigest, to offer an accessible overview of information drawn from the NICE guidelines. While MedDigest strives for accuracy in its educational summaries, this content has not been reviewed or produced by NICE. For comprehensive and definitive recommendations, please always refer to the complete NICE guidelines.

References

NICE (2017) Irritable bowel syndrome in adults: diagnosis and management. https://www.nice.org.uk/guidance/cg61