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In the past, it was thought that IBS was 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 relating to what causes IBS:
1. 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. This is seen as proof that serotonin plays a significant role in this disease.
2. Genetic: 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. 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. Researchers are now working on developing medicines that stabilise these mast cells in an attempt to control the symptoms (as is done with asthma patients).
Full thickness biopsy of the colon and jejunum show increased inflammatory lymphocytes in the colon. This gives weight to IBS having an inflammatory basis.
4. 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 (e.g. 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 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.
Research suggests that our gut microbial system may play a crucial role in the development of IBS. Recolonisation of the gut with Bifidobacterium and Lactobacillus species may improve IBS symptoms.
Reviewed by Dr Ismail Moola MBCHB (UCT) FCP (SA) Cert Gastro Phys (SA)
Specialist Physician / Gastroenterologist Netcare Sunninghill Hospital and part time Lecturer Department of Internal Medicine, Division of Gastroenterology, Wits University February 2015.
Previously reviewed by Dr E. Wilken (MBChB) Mmed (Int), gastroenterologist, May 2011
