Crohn’s Disease

Posted on 30 August 2013

Crohn’s disease can affect your entire gastrointestinal tract. Dr John Wright, gastroenterologist at Mediclinic Milnerton, explains what it is.

What exactly is Crohn’s disease: how is it different to other inflammatory bowel conditions, like ulcerative colitis?
Crohn’s disease stems from an over-reactive immune system, and it can affect the whole gastrointestinal tract, from the lips through to the colon. It’s the result of inflammation that starts because the immune system believes the gastrointestinal tract is under threat from a perceived danger. This danger is the vital missing link in understanding Crohn’s disease: it’s thought to be an infection or something in the diet, which the immune system hasn’t been exposed to before. So it starts to attack this threat and, in the process, damages the bowel wall, causing thickening and impairment anywhere along its length. The symptoms are characteristically cramps and general illness. Other symptoms could include arthritis and fever. Diarrhoea (with or without blood) is common.

Ulcerative colitis only affects the large bowel or colon and tends to just affect the surface lining of the colon, not the whole wall. The symptoms are usually diarrhoea with blood and cramps related to defecation.

How common is Crohn’s disease in SA?
There is varying population susceptibility. In the white population, about 6 in 100 000 people develop the disease each year. It’s probably slightly lower in the so-called coloured population, and least common in the black population.

Is it caused by genes or lifestyle factors?
A lot of research has gone into finding predisposing genetic factors. But if one identical twin has Crohn’s disease, the chances of the other twin developing the disease is only 20%. This suggests a powerful non-genetic cause of the disease. As yet, there is little support for lifestyle factors causing the disease.

How is a diagnosis typically made? Is a colonoscopy always needed?
Since most patients with Crohn’s disease develop problems at the end of the small bowel and the beginning of the colon, a colonoscopy is the most valuable diagnostic tool.

Is it true that the symptoms can go undetected for years?
The delay between onset of symptoms and diagnosis is typically 18 to 24 months.

How debilitating can Crohn’s disease be?
It’s a chronic condition which is probably lifelong. Before 1990, patients could become permanently crippled by the disease or the results of the surgery performed. It is now controllable, in the same way that hypertension and diabetes are. Patients treated with the modern drugs can expect a totally normal lifestyle with little risk of surgery. The problem is the cost of modern therapy, so in South Africa, not everyone has an equal chance of being properly treated.

For those in remission, what are possible causes of inflammation flare-ups?
Crohn’s disease is cyclical – it can flare and settle spontaneously. Why the disease should flare in a patient isn’t clear. Viral infections may precipitate an attack. Attacks are more common at certain times of the year, such as October to December.

Are there any promising developments in terms of treatment?
Modern therapy involves drugs that manipulate the immune system to reduce over-reactive responses.  The recent development of drugs that inhibit inflammatory processes in the gut only have been a breakthrough. But to develop these drugs, one needs about $2 billion per agent, and the process of making them available can take years in South Africa.

To contact Dr Wright, you can email him on or call on 021 555 2055 or 021 683 4600.

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