Updated 11 August 2014

Irritable bowel syndrome

Read about the causes of irritable bowel syndrome (IBS), treatment and diet for those living with the symptoms of spastic colon such as pain, bloating, and diarrhoea.



IBS (Irritable bowel syndrome) or Spastic colon is one of more than 20 functional gastrointestinal disorders and is characterised by stomach cramps, abdominal pain and intermittent diarrhoea. The term “functional” implies that the patient has symptoms related to the bowel, yet all the appropriate tests are normal. Abdominal pain is one of the functional diseases, but the pain differs from IBS. The symptoms of IBS are recurrent abdominal pain or discomfort directly associated with a change in the stool pattern (diarrhoea or constipation), and the pain or discomfort is relieved by passing stools. Most patients are also bloated. Typically, patients with this problem would get up in the morning, feeling fine, but as the day progresses, the bloating and pain or discomfort will start and intensify.


Because many sufferers do not report their symptoms to doctors, the exact number is unknown. It also seems to differ between countries, but the prevalence is estimated to be between 10 and 15% of the populations of most countries, and it accounts for to up to 28% of patients visiting a Gastro clinic.


The correct diagnosis and appropriate treatment regime present doctors with two major challenges. There are unfortunately no specific tests that can help us to make the diagnosis, and although we rely heavily on the symptoms discussed above, the diagnosis is often made by exclusion, especially by less experienced doctors. This implies that a lot of expensive tests are requested. 

Over the years symptom criteria moved from the Manning Criteria, Kruis score to the Rome I, Rome II and now Rome III criteria for a symptom-based diagnosis. We nowadays use the Rome III criteria  for the diagnosis.

The Rome III criteria are the following:

1. Recurrent abdominal pain or discomfort, at least 3 days per month for the last 3 months, associated with two or more of the following:

  • Improvement with defecation, and/or
  • Onset associated with a change in frequency of stool, and/or
  • Associated with a change in form (appearance) of stool.

2. Criteria fulfilled for the last 3 months with symptom onset six months prior to diagnosis.

Can we really rely that much on symptoms?

These symptoms are highly reliable. If any of the following occur with the typical symptoms, it is NOT IBS:

  • Any abnormal physical findings during examination
  • A raised erythrocyte sedimentation rate (a blood test that warns us something might be wrong).  It must be stated that a person with IBS can develop other diseases that can raise the ESR, but if a patient presents with new onset symptoms suggestive of IBS AND a raised ESR, it will turn out to be a different disease, such a Crohn’s disease or Celiac disease. 65% of patients with Crohn’s disease have IBS due to inflammatory damage to the nerve endings.
  • A raised white cell count (White cells help us to defend ourselves against infections.)
  • Anaemia (The blood has a pale appearance.)
  • Blood in the stool
  • Weight loss
  • Fever
  • The onset of IBS symptoms above the age of 35 years.  IBS can start at on older age, but it is very uncommon, and can be associated with the use of antibiotics for gastroenteritis.  We still need to do a full battery of tests to exclude other causes, such as cancer, before we make the diagnosis of IBS.
  • A family history of colon cancer or inflammatory bowel disease
  • Nocturnal symptoms, such as abdominal pain or discomfort
  • Faecal soiling


We do not know. In the past it was thought that to be a psychological or a stress-related problem, because a proportion of these patients were either physically or verbally abused, or a lot of them had other “stress-related” problems such as fibromyalgia.

There are several theories:

1. It might be a serotonergic problem: Serotonin is a substance that helps to move impulses from one nerve to the other and is present in abundance in the gastrointestinal system. It is involved in bowel movements. Two serotonergic drugs were developed that had a reasonably good impact on IBS, and that is seen as proof that serotonin plays a significant role in this disease.

2. It might be a genetic problem: Large studies with families and twins showed that it does seem to run in the family. They looked at the genes involved with serotonin, but could not link that to patients with IBS. This is however an exciting area for research.

3. It might be an inflammatory condition: Today, we know that some inflammation is involved in IBS, indicating some immune dysregulation. The marker for this inflammation is the mast cell and numerous mast cells are found in patients with IBS, especially near the nerve endings. The idea is now to develop medicines that stabilize these mast cells in an attempt to control the symptoms (as is done with asthma patients).

4. It might be bacterial overgrowth and altered gastrointestinal bowel flora: With the first breath that we take as newborn babies, bacteria enter and colonise our gut. Thus our environment at that moment plays such a crucial role in the nature of the gut flora.  Unfortunately, we cannot choose our environment at birth, and we get a lot of our gut flora from our mothers. Disturbance of the gut flora, such as taking antibiotics, can cause problems, such as diarrhoea. Peristaltic (wave-like, propulsive) movements of the bowel are essential to maintain a healthy gut flora. In IBS the motility is disturbed, and many of these patients have overgrowth of bacteria in the small bowel. This is the origin of symptoms such as bloating, abdominal pain and diarrhoea.

It was recently found that not only is the amount of bacteria important, the type involved in the overgrowth also plays a major role. In patients with an abundance of Lactobacillus and Veillonella, higher levels of acetic acid, propionic acid and organic acids were also found. Those patients with high levels of the former two acids had more severe symptoms and impaired quality of life.


There are the traditional therapies that treat the symptoms, such as bulking agents for constipation (i.e. Normacol), antidiarrheals (such as Loperamide) for diarrhoea and antispasmodics (i.e. Brevispas, Colofac) for pain. Peppermint oil and hyocine (Buscopan) also fall in this class, and both seem to be quite effective.

There are also emerging therapies on the horizon. They are based on the possible causes of IBS.

Serotonergic drugs: Prucalopride seems to do well in IBS patients with constipation and may become an important therapy in the near future.

Drugs that increase fluid secretion in the gut: There are two new drugs in this category that await approval in the USA. By stimulating the secretion of fluids, they improve the ease of stool passage and hence improve colon transit time.

Anti-inflammatory agents and mast cell stabilizers: Ketotifen, a well known anti-asthmatic drug has been investigated, and it seems to relieve the abdominal pain and other symptoms of IBS, including bloating. Prednisolone (a steroid drug used to suppress inflammation) did not prove of any value. However, mesalazine, an anti-inflammatory drug used to treat inflammatory bowel disease (such as Crohn’s disease and ulcerative colitis) reduced the inflammatory markers in the colon and increased the general well-being of IBS patients, but did not significantly improve the pain, bloating or bowel habits.

Antibiotics: The most promising of the emerging drugs is rifaximin, an antibiotic that is not absorbed from the gut.  Not only did it improve all the symptoms, the improvement was sustained for up to three months after stopping the medication.

There are many non-medical treatments available. Probiotics have been proved to be valuable to a certain subset of patients. A combination of two or more organisms seems to be more effective than preparations that contain only one organism.  Lactobacillus on its own does nothing for IBS, whereas a combination with Bifidobacterium is quite effective. Probiotics work via 3 mechanisms, i.e. direct antagonism (they secrete small molecules that have antimicrobial activities against other bacteria), immunomodulation (by stimulating our immune cells to kill off bad bacteria) and “exclusion” (they make the gastroinstestinal environment inhospitable to certain bacteria). Peppermint oil and Iberogast® give substantial relief and have been extensively used by medical practitioners. Unfortunately, many products such as Slippery Elm, have not been medically tested. Acupuncture is not very successful, but hypnosis rarely works, especially in people older than 50 years. One should also not discount the “placebo effect”. The placebo could be a sugar tablet or other ineffective substance, but has an up to 35% chance to be effective in the short term (up to 6 months). It is therefore difficult to evaluate the efficacy of any medication over the short term.

Changes in lifestyle or eating habits

Impact exercises definitely improve symptoms, especially constipation. There are quite a few “gas-forming” foods that can be excluded from the diet (fatty foods, onions, the cabbage family, dried beans and lentils including soy, citrus fruits, oats, nuts, visible fibre, avocado pears, coconut and yeast containing products). There is now an entity termed non-coeliac gluten intolerance. They are IBS patients that do not have coeliac disease when tested, but respond very well to a gluten free diet.

Pain, bloating, or an abnormal stool pattern

Most of the time it is difficult to diagnose oneself and it is best to see a doctor to confirm the diagnosis. If one has the classic IBS symptoms for years and a change in the symptoms occur, a doctor should be consulted. IBS does not make people immune to other diseases. Older patients should also consult a doctor when new abdominal symptoms appear.

Previously reviewed by Prof Don du Toit (M.B.Ch.B) (D.Phil.) (Ph.D) (FCS) (FRCS)

Reviewed by Dr E. Wilken (M.B.Ch.B) M.Med(Int), gastroenterologist, May 2011




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