IBS

• Irritable Bowl Syndrome (IBS)


  A functional bowel disorder (i.e. absence of abnormality) in which abdominal pain and bloating are associated with a change in bowel habits. The diagnosis is suggested by the presence of low-standing colonic symptoms, without any deterioration in the patient's general health. It can be chronic, episodic and debilitating.
• IBS classified by predominant stool type

  • Diarrhoea predominant — commonest
  • Constipation predominant
  • Mixed
  • Unclassified
• Epidemiology of IBS


  • Common condition (5-20% of population), with rates increasing
  • More likely to affect females: approximately twice as many women than men are affected
  • Usually affects younger adults (20-39 years) and onset after the age of 50 years is unusual
• Aetiology of IBS


  There are no specific anatomical, biochemical or microbiological factors to explain the aetiology of IBS, but it is now clearly understood be multifactorial. Many factors can contribute to disease expression and include motility dysfunction, diet and genetics. In a small proportion of cases, symptoms appear after bacterial gastroenteritis. Psychological factors also influence symptom reporting and consultation, and some studies have shown that patients who suffer from higher levels of stress or depression experience worse symptoms compared with other patients. Flare-up of symptoms has also been associated with periods of increased stress.
• Mechanisms of IBS


  • Visceral hypersensitivity
  • Abnormal GI immune function
  • Changes in gut microbiome
  • Abnormal autonomic activity
  • Altered brain-gut interactions
  • Abnormal GI motility
• Multi-factorial factors contributing to IBS

  • Dietary
  • Food intolerances, caffeine, lactose
  • Gastroenteritis
  • Hormonal
  • Psychological (Stress/anxiety/depression)
  • Genetic
  • GI inflammation (secondary to IBD)
  • Drugs (Antibiotics)
• Symptoms of IBS


  • Abdominal pain or discomfort, located especially in the left lower quadrant of the abdomen, which is often relieved by defecation or passage of wind
  • Altered defecation, constipation or diarrhoea, with associated bloating
  • Diarrhoea on awakening and shortly after meals
  • Feeling of incomplete bowel clearance
  • Flatulence
  • Nausea
  • Belching
  • Poor appetite
  • Fullness after eating
  • Heartburn
  • Headache
  • Tiredness
  • Backache
  • Muscle pains
  • Gynaecological symptoms
  • Bladder symptoms (Frequency, Urgency, Nocturia)
• Criteria for IBS diagnosis

  • Abdominal pain/discomfort (main) that is relieved by defaecation and associated with altered bowel frequency or stool form
  • At least two of the following: Abdominal bloating (more common in women than men), distension, tension or hardness; Altered stool passage (straining, urgency, incomplete evacuation)/change in bowl movement; Symptoms made worse by eating; Passage of mucous; Lethargy, nausea, backache and bladder symptoms
• Considerations for IBS diagnosis

  • IBS usually affects people <45 years. Particular care is required in labelling middle-aged (i.e., 45 years old) and older patients with IBS when presenting with bowel symptoms for the first time, as prevalence of organic bowel disease is more common after the age of 45
  • IBS tends to be episodic. The patient might have a history of being well for a number of weeks or months in between bouts of symptoms. Often, patients can trace their symptoms back many years, even to childhood
  • The nature of pain experienced by patients with IBS is very varied, ranging from localized and sharp to diffuse and aching. It is therefore not very discriminatory; however, the patient will probably have experienced similar abdominal pain in the past. Any change in the nature and severity of the pain is best referred for further evaluation
  • Pain from IBS is normally located in the left lower quadrant
  • Patients with IBS do not have textbook definitions of constipation or diarrhoea, but bowel function will be different than normal. Constipation-predominant IBS is more common in women.
• Management/treatment of IBS


  1. Avoid exacerbating or triggering factors, e.g. diet

  2. Lifestyle measures such as exercise and stress

  3. Eat regular meals with healthy, balanced diet + adjust fibre intake depending on symptoms

  4. Adequate fluid intake - 8 cups a day

  5. See patient in two months

  6. If symptoms persist with lifestyle advice, refer to dietician (low FODMAP diet) and/or drug therapy

  7. Tailor choice of drug to predominant symptom: constipation, diarrhoea and/or abdominal pain
• Dietary advice for IBS

  • Regular meals – small & frequent, pace
  • 8 cups of fluid per day
  • Restrict caffeinated drinks to three cups per day
  • Reduce intake of alcohol and fizzy drinks
  • Reduce intake of 'resistant starch' (starch that resists digestion in the small intestine and reaches the colon intact), often found in processed or re-cooked foods
  • Limit fresh fruit to three portions (of 80 g each) per day
  • For constipation, gradually increase fibre e.g. wholegrains, oats, fruit and veg, linseeds (no extra wheat bran)
  • For diarrhoea, avoid sorbitol and limit intake of high-fibre food (for example, wholemeal or high-fibre flour and breads, cereals high in bran, and whole grains such as brown rice)
  • For wind and bloating consider increasing intake of oats (for example, oat-based breakfast cereal or porridge) and linseeds (up to one tablespoon per day) and reduce gas-producing foods e.g. beans, chewing gum
  • Dietician may recommend a low FODMAP diet (under specialist supervision)
  • Avoid foods that are harder for the gut to break down: Milk, Wheat products, Some fruit + veg
• Antispasmodic drugs for IBS

  • Alverine: Acts directly on smooth muscle of gut, causes relaxation, thus reducing pain, 60-120mg up to tds (three times a day)
  • Mebeverine: Acts directly on smooth muscle of intestine, 135mg tds, 20min before meals, generally considered first-line, not to be used if pregnant or breast-feeding or in children, side effects are rare, review at three months
  • Antimuscarinic antispasmodics: Poorly absorbed, poorly selective, acts directly on gut, contraindicated in glaucoma, prostate, elderly and pregnant, more side effects, less used, 10-20mg up to qds (4 times a day), can be P (pharmacy/OTC medicine)
  • Peppermint oil: Relaxant on smooth muscle, can cause heart burn, 1-2 caps 0.2ml) tds, 15-30min before meals, do not chew – irritates mouth + oesophagus, enteric-coated preparation
• Other drugs for IBS

  • Laxatives: Bulk-forming (ispaghula husk=soluble fibre) + increase fluid intake, adjust dose to produce regular, soft stool, review after 3 months, avoid lactulose
  • Anti-diarrhoeal drugs: Loperamide, dose variable, dependent on frequency of symptom – usually short term (chronic dose vs acute dose)
  • TCAs: Regular low dose, for persistent symptoms, best for IBS with pain, diarrhoea, off-label indication e.g. amitriptyline, review after 4 weeks, can increase dose, review every 6 months, if ineffective/CI, consider SSRI (off-label)
  • Probiotics: May help, some evidence, 12 week trial, change brand if ineffective, possibly try yoghurt or kefir (fermented milk drink), do not recommend aloe vera products
• Blood in stool is unusual in IBS and can suggest inflammatory bowel disease. Patients with this symptom should be referred ASAP.
• Fever, nausea and/or vomiting or severe abdominal pain are not usually associated with IBS and suggest origin of symptoms from other abdominal causes. Patients with these symptoms should be referred.
• IBS is unusual in children 16 years and patients 45 years with recent changes to bowel habits. These patients should be referred for further investigation.
• Steatorrhoea is associated with malabsorption syndromes, not IBS.