Irritable bowel syndrome

Irritable Bowel Syndrome (IBS) is a functional gastrointestinal disorder characterised by a range of symptoms including abdominal pain, bloating, and changes in bowel movements such as diarrhoea or constipation.

Symptoms often persist over long periods and can significantly impact the quality of life, leading to missed work or school. The condition is associated with psychiatric illnesses including anxiety and depression, and often presents in individuals before the age of 45.

Causes and Risk Factors

The exact cause of IBS is unknown, but it is believed to be multi-factorial involving the gut-brain axis, gut motility, visceral hypersensitivity, infections, neurotransmitters, genetic factors, and food sensitivity. Important risk factors include genetic predisposition, psychological stress, childhood abuse, food poisoning, and psychiatric illnesses. Stressful life events or intestinal infections can trigger the onset of IBS.

Stress

Psychological stress is a significant factor and can exacerbate IBS symptoms. The hypothalamic-pituitary-adrenal axis and the sympathetic nervous system, both of which regulate stress responses, operate abnormally in IBS patients. High levels of anxiety and sleep disturbances are common, and childhood abuse is often linked to the development of IBS.

Post-Infectious IBS

Around 10% of IBS cases are triggered by an acute gastroenteritis infection, which increases gut permeability and leads to chronic inflammation. This subtype is typically diarrhoea-predominant.

Signs and Symptoms

Primary symptoms include abdominal pain, bloating, and changes in bowel habits, often relieved by bowel movements. IBS can also manifest with gastroesophageal reflux, genitourinary symptoms, fibromyalgia, headaches, backaches, and psychiatric symptoms such as depression and anxiety.

Diagnosis

Diagnosis is based on symptoms and the exclusion of other conditions. The Rome IV criteria are commonly used, which require recurrent abdominal pain for at least one day a week in the last three months, along with stool-related criteria. Differential diagnosis should rule out conditions like celiac disease, inflammatory bowel disease, and colon cancer. Investigations often include stool microscopy, blood tests, abdominal ultrasound, and endoscopy.

Treatment

Dietary Changes

Dietary interventions include increasing soluble fibre intake and adopting a low-FODMAP diet, which restricts fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. This diet aims to reduce symptoms like bloating and flatulence but should be used short-term under specialist guidance.

Medication

Medications for IBS are aimed at symptom relief. Antispasmodics such as dicyclomine can reduce cramps and diarrhoea. Antidepressants, especially tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs), can alleviate overall symptoms and pain. Laxatives like polyethylene glycol and sorbitol may help with constipation, and probiotics can balance gut flora. Peppermint oil and rifaximin have also shown effectiveness in symptom management.

Psychological Therapies

Psychological therapies, including cognitive behavioural therapy and stress management techniques, may reduce the severity of IBS symptoms. Regular physical activity is also beneficial.

Epidemiology

IBS affects around 10-15% of people in the developed world and up to 45% globally. It is more common in women in Western countries but not significantly different between genders in East Asia. The condition is less common with advancing age and does not affect life expectancy.

History and Society

The term "irritable bowel syndrome" was first used in 1944. IBS has significant economic implications, with direct medical costs estimated between $1.7 and $10 billion annually in the United States. Indirect costs, including lost productivity, add another $20 billion.

This comprehensive overview of IBS highlights its complex aetiology, varied symptoms, diagnostic criteria, and multifaceted treatment approaches, essential knowledge for healthcare professionals preparing for exams or clinical practice.

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Self-assessment MCQs (single best answer)

Which of the following is NOT a common symptom of IBS?

What percentage of IBS cases are typically triggered by an acute gastroenteritis infection?

Which dietary intervention is commonly recommended for IBS patients?

Which medication is typically used to reduce cramps and diarrhoea in IBS patients?

Which of the following is a risk factor for developing IBS?

According to the Rome IV criteria, how often must abdominal pain occur to consider an IBS diagnosis?

Which psychological therapy is commonly used to manage IBS symptoms?

What is the estimated prevalence of IBS in the developed world?

Which of the following conditions must be ruled out when diagnosing IBS?

The term "irritable bowel syndrome" was first used in which year?