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 (IBD) 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 inflammatory bowel diseases
Much work is being undertaken worldwide into the possible causes of IBD, 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.
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.