Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome (IBS) refers to a disorder that involves abdominal pain and cramping, as well as changes in bowel movements. It is not the same as inflammatory bowel disease (IBD), which includes Crohn’s disease and Ulcerative Colitis.

How is IBS diagnosed?

Irritable bowel syndrome (IBS) is a diagnosis of exclusion. This means that other causes for the symptoms of irritable bowel syndrome need to be first excluded before such a diagnosis can be made. This usually involves the need for a gastroscopy and colonoscopy to exclude certain pathology within the gastrointestinal tract.

Cause of IBS

There are many possible causes of IBS. For example, there may be a problem with muscles in the intestine, or the intestine may be more sensitive to stretching or movement. There is no problem with the structure of the intestine.

Stress can worsen IBS. The colon is connected to the brain through nerves of the autonomic nervous system. These nerves become more active during times of stress, and can cause the intestines to squeeze or contract more. People with IBS may have a colon that is over-responsive to these nerves.

IBS can occur at any age, but it often begins in adolescence or early adulthood. It is more common in women. About 1 in 6 people in Australia have symptoms of IBS.

Symptoms of IBS

Symptoms range from mild to severe. Most people have mild symptoms. Symptoms vary from person to person.

Abdominal pain, fullness, gas, and bloating that have been present for at least 6 months are the main symptoms of IBS. The pain and other symptoms will often:

  • Occur after meals
  • Come and go
  • Be reduced or go away after a bowel movement
  • People with IBS may switch between constipation and diarrhoea, or mostly have one or the other.
  • People with diarrhoea will have frequent, loose, watery stools. They will often have an urgent need to have a bowel movement, which is difficult to control. This urge rarely wakes a person from their sleep.
  • Those with constipation will have difficulty passing stool, as well as less frequent bowel movements. They will often need to strain and will feel cramping with a bowel movement. Often, they do not eliminate any stool, or only a small amount.

For some with IBD, the symptoms may get worse for a few weeks or a month, and then decrease for a while. For others symptoms are present most of the time and may even slowly increase.

Investigations for IBS

There is no test to diagnose IBS, but tests may be done to rule out other problems and include stool cultures to rule out infection of the colon (colitis), gastroscopy to rule out a disorder of failed absorption of the small bowel (celiac disease and lactose intolerance), and colonoscopy to rule out disorders of the colon such as colitis, diverticulosis, and cancer than can often mimic IBS.

Colonoscopy is particularly important for those with IBS symptoms who:

  • had their symptoms begin later in life (e.g. over age 40-50)
  • have symptoms such as weight loss or bloody stools
  • have iron deficiency anaemia with a low haemoglobin.

Lifestyle treatment of IBS

Once the diagnosis has been established with a normal gastroscopy and colonoscopy, the goal of treatment is to relieve IBS symptoms.

Lifestyle changes can be helpful in some cases of IBS. For example, regular exercise and improved sleep habits may reduce anxiety and help relieve bowel symptoms.

Dietary changes can be helpful. However, no specific diet can be recommended for IBS in general, because the condition differs from one person to another. The following changes may help:

  • Avoid foods and drinks that stimulate the intestines (such as caffeine, tea, or colas)
  • Avoid large meals
  • Avoid wheat, rye, barley, chocolate, milk products, and alcohol
  • Increase dietary fibre

Medical treatment of IBS

Talk with your GP before taking over-the-counter medications. No one medication will work for everyone. Medications need to be tailored to meet the symptoms, which typically alternate in IBS. Medications your doctor might try include those used to treat non-infectious diarrhoea, such as diphenoxylate and atropine (Lomotil®) or loperamide (Imodium® or Gastrostop®). These medications work as a ‘chemical plug’ and must not be used if there is any chance that diarrhoea is due to infection.

If crampy pains are the main symptom, then medications that relax muscles in the intestines such as hyoscine (Buscopan®) may help. Fibre supplements can make symptoms worse, as they increase fluid consistency of stool and methane production leaking to crampy pain and diarrhoea.

Expectations for IBS

IBS may be a lifelong condition. For some people, symptoms are disabling and reduce the ability to work, travel, and attend social events. Symptoms can often be improved or relieved through treatment. IBS does not cause permanent harm to the intestines, and it does not lead to a serious disease, such as cancer.

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