What are inflammatory bowel diseases (IBD)?
Ulcerative Colitis (UC) and Crohn’s Disease (CD) are both relatively rare diseases. They are chronic disorders causing the formation of areas of inflammation and ulceration in various sections of the digestive tract. This inflammation causes persistent and frequent diarrhoea (often blood stained and passed with urgency), abdominal pain, fever, tiredness and loss of weight.
Inflammatory bowel diseases are mainly seen in the industrialised parts of the world. They affect all races, though in some populations the incidence is lower. People who move from underdeveloped to developed parts of the world attain the same level of risk of developing IBD as the rest of the population after some time.
There is generally a higher incidence in northern latitudes compared with southern latitudes, and in urban areas over rural.
Development of inflammatory bowel diseases
Ulcerative Colitis and Crohn’s Disease affect all age groups and can start at any age, but the highest number of new cases occurs in young people.
The course of UC and CD varies unpredictably in severity and usually cycles between periods of active inflammation (flare-ups) and periods of low activity or even remission when the patient feels well and is free from symptoms.
In their early stages UC and CD may be difficult to diagnose. Their symptoms resemble that of each other and other conditions, such as infectious gastroenteritis and irritable bowel syndrome. It may sometimes take years before a correct diagnosis is made and a treatment used which is compatible with the patients and their way of life.
Causes of IBD
Much work is being undertaken worldwide into the possible causes of inflammatory bowel diseases, but despite many theories the cause and the exact changes occurring in the body remain poorly understood.
There seems to be a genetic and environmental impact behind IBD, causing an imbalance in the inflammatory processes of the gut. It is thought that viruses, bacteria, a highly refined diet, stress and smoking may contribute.
Ulcerative Colitis
The inflammation in Ulcerative Colitis exclusively affects the superficial layer (the mucosa) of the large intestine. It almost always involves the rectum and spreads in a continuous manner from there. In a small percentage of patients, the whole of the large bowel is involved. The most common age group for UC to be diagnosed is within the 15 to 35 year-olds, with a second peak being seen in 55 to 70 year-olds. Up to 400 people per 100,000 inhabitants suffer from Ulcerative Colitis worldwide.
Crohn’s Disease
Unlike Ulcerative Colitis, Crohn’s Disease can affect any part of the GI tract, although it mainly presents itself in the small bowel. In Crohn’s, the disease most commonly affects just the small intestine (40%), though it can often affect both the small and large intestine (colon) (30%) and in other cases just the colon (30%).
Crohn’s Disease affects up to 150 people per 100,000 inhabitants, and is most commonly diagnosed in the 15 to 25 year-old age groups. Recent statistics appear to indicate a rise in the number of new cases, but it is not clear why this may be.
About 15 to 20 per cent of people with Crohn’s Disease have a close relative with some form of IBD, suggesting any genetic predisposition in these patients.
Complications of IBD
In cases where diarrhoea is very frequent, or bloody and severe, water loss and poor absorption of nutrients may occur, leading to anaemia, dehydration and severe weight loss.
The inflammation in Crohn’s Disease may lead to strictures (narrowing) of the bowel which helps create abdominal pain. Severe cases may lead to life-threatening complications such as blockage or perforation of the bowel, and there has been a definite link between patients with colitis having an increased risk of developing colorectal cancer.
The risk of colorectal cancer increases with the extent and severity of the disease, the age it started and how long the patient has had the disease. For patients suffering from Ulcerative Colitis, recent trials have shown the risk of colorectal cancer at 10, 20 and 30 years after the diagnosis of the onset of their disease as being 2, 8 and 18 per cent higher (respectively) than the incidence seen in the general population.