Summary

  • Irritable bowel syndrome is characterised by abdominal pain, bloating and alternating constipation and diarrhoea.
  • The cause is unknown, but environmental factors – such as changes of routine, emotional stress, infection and diet – can trigger an attack.
  • Treatment options include careful changes to diet over a period of time, laxatives or antidiarrhoea medication, and antispasmodics.
Around one in five Australians experiences the unpleasant symptoms of irritable bowel syndrome (IBS) at some time. These include abdominal pain, mucus in the stools, and alternating diarrhoea and constipation. Other terms for irritable bowel syndrome include ‘spastic colon’ and ‘irritable colon’. It seems that people with IBS have sensitive bowels that are easily ‘upset’. More women than men are prone to IBS, and symptoms tend to first occur in early adulthood.

The cause is unknown, but environmental factors such as changes of routine, emotional stress, infection and diet can trigger an attack. Research has shown that the neurotransmitter serotonin may be important in the symptoms of IBS, by altering the function of nerve cells in the bowel and causing changes in pain sensation and bowel function.

Irritable bowel syndrome doesn’t cause lasting damage and doesn’t contribute to the development of serious bowel conditions, such as cancer or colitis.

Symptoms of IBS


Some of the more common signs of irritable bowel syndrome include:
  • abdominal pain or cramping that is often relieved by passing wind or faeces
  • alternating diarrhoea and constipation
  • a sensation that the bowels are not fully emptied after passing a motion
  • abdominal bloating
  • mucus present in the stools
  • nausea.
None of these symptoms are exclusive to IBS. It is unusual for IBS to produce these symptoms, for the first time, after the age of 40.

Main IBS categories


Irritable bowel syndrome can be subdivided into three major categories:
  • Constipation-predominant – the person tends to alternate constipation with normal stools. Symptoms of abdominal cramping or aching are commonly triggered by eating.
  • Diarrhoea-predominant – the person tends to experience diarrhoea first thing in the morning or after eating. The need to go to the toilet is typically urgent and cannot be delayed. Incontinence may be a problem.
  • Alternating constipation and diarrhoea.

Cause of IBS


The underlying cause of irritable bowel syndrome is still unknown, but certain factors have been found to ‘trigger’ attacks in susceptible individuals. These include:
  • Infection – an episode of gastroenteritis will often result in persistent bowel symptoms, long after the offending bacteria or virus has been eliminated. The cause of this is unknown, but may involve changes to nerve function in the bowel or changes in the normal bacterial population of the bowel. Up to 25 per cent of IBS may be due to this problem.
  • Food intolerance – impaired absorption of the sugar lactose (found in dairy and many processed foods) is the most common dietary trigger for IBS. Other sugars believed to trigger IBS are fructose (present in many syrups) and sorbitol.
  • General diet – low-fibre diets can exacerbate the constipation of constipation-predominant IBS. Some people find spicy or sugary foods cause problems. However, many experts are sceptical about the role of general diet, once specific food intolerances have been eliminated.
  • Emotional stress – strong emotions, such as anxiety or stress, can affect the nerves of the bowel in susceptible people.
  • Medication – certain types (such as antibiotics, antacids and painkillers) can lead to constipation or diarrhoea.

Diagnosis of IBS


If you suspect you have irritable bowel syndrome, it is important to seek medical advice to make sure your symptoms aren’t caused by any other illness, such as diverticulitis, inflammatory bowel disease or polyps. Coeliac disease (an immune intolerance to gluten, present in wheat and other grains) may produce many of the same symptoms as IBS. Lactose intolerance may produce bloating, cramps and diarrhoea.

Diagnosis methods include:
  • full medical check-up
  • blood tests, including blood tests for coeliac disease
  • stool tests
  • investigation of the bowel lining by inserting a small tube (sigmoidoscopy)
  • investigation of the bowel under sedation (colonoscopy) or barium enema, if necessary.

Treatment for IBS


IBS cannot be cured with medication or special diets. The primary preventative measure is to identify and avoid individual triggers. Treatment options may include:
  • a modest increase in dietary fibre, together with plenty of clear fluids
  • reducing or eliminating common gas-producing foods, such as beans and cabbage
  • reducing or eliminating dairy foods, if lactose intolerance is a trigger
  • antidiarrhoea medication, such as imodium or lomotil – these can be an essential part of management in those with diarrhoea-predominant IBS
  • pain-relieving medication – opiates such as codeine can provide effective pain relief. One of their most common side effects, constipation, may also relieve the diarrhoea of diarrhoea-predominant IBS
  • treatments to treat constipation
  • antispasmodic drugs, which may ease cramping – examples include mebeverine, belladonna, hyoscine and peppermint oil capsules
  • tricyclic antidepressants – these can be effective in treating the pain of IBS, but are best prescribed for a trial period with monitoring of symptoms. Use of these does not mean that IBS is caused by depression
  • stress management, if stress seems to be triggering the attacks
  • establishing eating routines and avoiding sudden changes of routine.
A a group of carbohydrates called FODMAP is now believed to contribute strongly to symptoms of IBS in many people. A low-FODMAP diet can be tried in these instances. This diet can be commenced with the supervision of a dietician experienced in management of IBS.

Specific treatments for IBS are not approved for use


A small number of medications have been developed to treat IBS and have been shown to be effective in selected groups in clinical trials. These work on the interaction between serotonin and nerve cells of the colon. They include alosetron, cilansetron and tegaserod. Safety concerns with these three medications has led to their withdrawal from the market, or restricted use only, and none are presently licensed in Australia.

Find an experienced health professional


People with IBS can become frustrated and feel their symptoms are not treated seriously. These frustrations, along with sometimes inappropriate therapy, can often make the symptoms worse. Finding a therapist with experience in the successful treatment of IBS is important.

Where to get help

  • Your doctor
  • Irritable Bowel Information and Support Association Tel. (07) 3372 2091
  • Dietitians Association of Australia Tel. 1800 812 942

Things to remember

  • Irritable bowel syndrome is characterised by abdominal pain, bloating and alternating constipation and diarrhoea.
  • The cause is unknown, but environmental factors – such as changes of routine, emotional stress, infection and diet – can trigger an attack.
  • Treatment options include careful changes to diet over a period of time, laxatives or antidiarrhoeals, and antispasmodics.
References
  • Irritable bowel syndrome (IBS), Gastroenterological Society of Australia (GESA). More information here.
  • Moleski S 2013, ‘Irritable bowel syndrome (IBS)’, The Merck Manual of Diagnosis and Therapy, Merck & Co. More information here.
  • Tack J, Fried M, Houghton LA et al. 2006, ‘Systematic review: the efficacy of treatments for irritable bowel syndrome – a European perspective’, Alimentary Pharmacology and Therapeutics, vol. 24, no. 2, pp. 183–205. More information here.
  • Evans BW, Clark WK, Moore DJ, Whorwell PJ 2008, ‘Tegaserod for the treatment of irritable bowel syndrome’, The Cochrane Database of Systematic Reviews, vol. 1, CD003960. More information here.
  • Heading R, Bardhan K, Hollerbach S et al. 2006, ‘Systematic review: the safety and tolerability of pharmacological agents for treatment of irritable bowel syndrome – a European perspective’, Alimentary Pharmacology and Therapeutics, vol. 24, no. 2, pp. 207-236. More information here.
  • Low FODMAP diet for irritable bowel syndrome, Medicine, Nursing and Health Sciences, Monash University. More information here.

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This page has been produced in consultation with and approved by: Canberra Hospital - Gastroenterology Unit

Last updated: May 2015

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