Irritable Bowel Syndrome

Definition/diagnostic criteria Irritable bowel syndrome (IBS) is a functional bowel disorder characterised by symptoms of abdominal pain associated with defecation or a change in bowel habits. The Rome IV criteria, widely accepted in the UK, include recurrent abdominal pain on average at least one day per week in the preceding three months, associated with two or more of the following: related to defecation, associated with a change in stool frequency, or associated with a change in stool form.

Epidemiology IBS has a significant prevalence in the UK, affecting an estimated 10-20% of the population, with a higher incidence in females and typically presenting before the age of 50.

Diagnosis
Clinical features: The diagnosis of IBS in primary care is largely symptom-based.

• Key symptoms include abdominal pain, bloating, and altered bowel habits (either diarrhoea, constipation, or a combination).
• Symptoms often fluctuate over time and can be exacerbated by stress or food intake.

Investigations: Diagnosis is primarily clinical, with investigations aimed at ruling out other conditions.

• Recommended blood tests include full blood count, inflammatory markers and coeliac serology.
• A faecal calprotectin is advisable to help rule out inflammatory bowel disease, especially if the patient had diarrhoea and is 45 or younger.
• In certain circumstances a FIT test and/or referral (which may be urgent to rule out bowel cancer) might be indicated.

Treatment Management is symptom-based and multidisciplinary, involving dietary, pharmacological, and psychological interventions.

• Dietary advice includes regular meals, avoidance of insoluble fibre and ‘trigger’ foods, and consideration of a low FODMAP diet for those with predominant bloating or distension.
• Pharmacological treatment depends on the predominant symptom:
  – Antispasmodics (e.g., mebeverine) are recommended for pain, loperamide for diarrhoea, and laxatives (preferably soluble fibre such as ispaghula husk) for constipation.
  – Antidepressants, such as low-dose tricyclic antidepressants (e.g., amitriptyline), can be used for pain management.
• Psychological interventions, particularly cognitive behavioural therapy (CBT), have shown effectiveness in managing IBS symptoms, especially in patients with severe symptoms or psychological comorbidities.

Prognosis: IBS is a chronic condition, but the prognosis is generally good. Most patients can achieve symptom control with appropriate management. However, the condition can significantly impact the quality of life and may be associated with psychological disorders such as anxiety and depression. Long-term follow-up in primary care is often necessary to manage fluctuating symptoms and reassess treatment strategies.