It seems every second person you talk to nowadays has irritable bowel syndrome (IBS), but what exactly is it? Dr Trevlyn Burger sheds insight.

Irritable bowel syndrome is synonymous with ‘leaky gut’ or ‘spastic colon’. It is a condition that affects the function and behaviour of the intestine. It is the most commonly diagnosed gastrointestinal condition and thus has a large impact on healthcare costs. An estimated 10 to 20% of the general population experience symptoms of IBS. Many people experience only mild symptoms, but for some, symptoms can be severe and impact on quality of life and work productivity.

Symptoms
The primary symptoms are abdominal cramping and bloating, a feeling of incomplete evacuation, and altered bowel movements. Some people have frequent, watery bowel movements while others are constipated, and some switch back and forth between diarrhoea and constipation.

Causes
Despite intensive research, the cause of irritable bowel syndrome remains incompletely understood. IBS is a heterogeneous disorder and no single abnormality accounts for IBS symptoms in all patients. Postulated causes include:

• Post infectious – Some people develop IBS after a severe gastrointestinal infection (e.g. salmonella or campylobacter jejuni). It is not, however, clear how infections trigger IBS.
• Food intolerances – This raises the possibility that it is caused by food sensitivity or allergy. The best way to detect an association between symptoms and food sensitivity is to eliminate certain food groups systematically (an elimination diet). Note: eliminating foods without assistance from a nutritionist can lead to omission of important sources of nutrition. Several foods known to cause symptoms include gluten, dairy, legumes, and cruciferous vegetables amongst others.
• Heightened sensitivity of the intestines to normal sensations (visceral hyperalgesia) – The theory proposes that nerves in the bowels are overactive in people with IBS, thus normal amounts of gas or movement are perceived as excessive and painful.
• Anxiety and stress – These are known to affect the intestine. A strong association exists in patients who have experienced significant early-life emotional trauma.
• Abnormal contractions of the intestines – There may be an intense prolonged, spastic contraction due to an abnormal electrical system. When two parts of the colon contract simultaneously, the colon between stretches like a balloon resulting in bloating and distension.
• Alteration in faecal microflora – Emerging data suggests that the faecal microbiota (normal bacterial load in the intestine) in individuals with IBS differs from that of healthy controls.
• Genetics – Studies suggest a genetic susceptibility in some patients with IBS.
• Bile acid malabsorption – In some patients, excess bile in the colon may result in diarrhoea-predominant IBS.

Diagnostic approach

Many disorders present with symptoms similar to irritable bowel syndrome, thus it is important to exclude other causes. ‘Alarm’ or atypical symptoms that are not compatible with IBS include:

• Rectal bleeding.
• Nocturnal waking with pain and bowel movements.
• Weight loss.
• Laboratory abnormalities, such as anaemia, elevated inflammatory markers or electrolyte disturbances.
• Family history of colorectal cancer, inflammatory bowel disease or celiac disease.

The diagnostic evaluation depends on whether the predominant symptoms are diarrhoea or constipation. The most common conditions that need to be excluded are inflammatory bowel syndrome, hormonal disturbances, infections, diverticular disease and colorectal cancer.

In diarrhoea-predominant, a stool sample is sent for testing and celiac disease needs to be excluded. In constipation-predominant, other causes of constipation, e.g. an underactive thyroid or high calcium need to be excluded.

All persons over the age of 50 years should have a colonoscopy at least once a year.

Treatment

• Education and reassurance – It is important to establish a therapeutic clinician-patient relationship to validate the patient’s symptoms, and to understand that IBS does not increase the risk of cancer, but that it is a chronic (long-standing) disease. In patients with mild and intermittent symptoms that do not impair quality of life, we initially recommend lifestyle and dietary modification alone. In those with more significant symptoms, we suggest adjunctive pharmacological therapy.
• Dietary modification – A careful dietary history may reveal patterns of symptoms related to specific foods. More than half of patients’ symptoms are improved by eating smaller meals, avoiding milk products, avoiding fatty foods and gluten.

Patients with IBS may benefit from exclusion of gas-producing foods; a diet low in fermentable oligo-, di- and monosaccharide’s and polyols (FODMAPS), as it is thought that there are bacteria in the colon that ‘feed off’ these foods changing bowel function and behaviour.

There is insufficient evidence to support routine food allergy testing in patients with IBS. The role of fibre is controversial, but given the absence of serious side effects and potential benefits, psyllium and ispagulla should be considered in those constipated.

• Psychological intervention – Cognitive behavioural therapy may be of benefit.
• Physical activity – This is advised to be of benefit.
• Pharmacological therapy
  • Constipation-predominant:
    Loperamide (Imodium) is usually the first line of treatment. Lubiprostone (Amitiza) and linaclotide as second line (not freely available in South Africa).
    
  • Diarrhoea-predominant:
    Antidiarrheal agents, such as loperamide, as first line treatment. Bile acid sequestrants, such as cholestyramine (Questran and Questran Lite), are used as second line treatment.
  • Abdominal pain and bloating:
    • Antispasmodics as needed.
    • Iberogast
    • Colpermin
    • Simethicone
      
  • Antidepressants – Tricyclic antidepressants (TCAs) are considered in patients in whom laxatives, loperamide or antispasmodics have not helped. Selective serotonin reuptake inhibitors can also be considered.
    
  • Antibiotics – Not routinely recommended. A two-week trial of rifaximin may give long-lasting symptom relief, emphasising the role of the gut bacteria. (Microbiome)
    
  • Probiotics – Not routinely recommended. Although, they have been associated with an improvement in symptoms. The magnitude of benefit and the most effective species and strain are uncertain. Faecal microbiota transplants (stool transplants) are being evaluated in clinical trial.
    
  • Other therapies – Herbs, acupuncture, enzyme supplements and mast cell stabilisers have been evaluated, but their role in irritable bowel syndrome remains uncertain.

Patients with refractory symptoms should be carefully reassessed, paying specific attention to the type of ongoing symptoms, the degree to which symptoms have changed, compliance with medications, and the presence of any alarm symptoms.

Reassurance that there is no sinister underlying illness is of great importance with these patients as their pain and bowel habits are often abnormal and real, and this can cause anxiety.