Crohn's Disease

Crohn’s disease (CD) is a type of inflammatory bowel disease named after Burrill Crohn, a gastroenterologist in New York who described a number of patients with the condition in the 1930s. CD is a chronic disorder, meaning it continues for a lengthy period of time, maybe even lifelong. The disease often starts in adolescence or young adulthood. However, it can occur at any age, and there is a second spike in onset of the disease later on in life.

There are essentially three types of CD, one affecting the small (upper) bowel, one affecting the last part of the small bowel and first part of the colon, and one affecting the large bowel (colon).

Typical symptoms of CD are abdominal pain and diarrhoea. Some people also lose blood in their stools. Other symptoms can occur, depending on which part of the bowel is affected. CD can come and go, and there is generally a phase of healing in between. Unfortunately, because of this healing pattern, some people develop a narrowing of the bowel in the affected area, called a stenosis. When this narrowing becomes severe, patients can develop severe pain, nausea, and vomiting.

Around 50% of patients with CD develop problems around their back passage. These include infections and anal fissures (small tears in the lining of the anal canal) and anorectal fistulas (abnormal connections between the lining of the rectum and the outside skin around the anus). People with this disease can also develop fistulas, where abnormal connections develop between one piece of bowel and another, between the bowel and another organ, or between a piece of bowel and the skin surface. Many patients with the disease also have skin tags (harmless growths) around the anus and some develop bowel incontinence.

In younger people, CD may affect growth. Other organs can also be affected, include the eye, liver, joints, and skin. There is also an increased risk of developing a blood clot (thrombosis) in the legs and potential movement of the clot to the lungs (pulmonary embolism). There are a variety of conditions of the gum and mouth that can also cause problems in CD.

Some people with CD have a reduced ability to absorb nutrients and develop malabsorption syndrome, in which essential nutrients are not able to enter the bloodstream. Others actively avoid eating because there is a narrowing in their bowel or because they are trying to avoid pain and/or diarrhoea. Therefore, patients with CD are prone to losing weight very easily.

No one really knows what causes CD. The disease definitely has a genetic component. If you have a brother or sister with CD, you are 30 times more likely to develop the disease then someone who has not. To date, over 30 genes have been found to be linked to CD.

We also know that the environment plays a part as well. The disease is mostly found in industrialised countries, and is associated with having more animal and milk protein and less vegetable protein in the diet. Smoking increases the severity and risk of recurrence of CD, but is unlikely to cause the disease.

There is no evidence that CD is made worse by stress. However, many patients with CD also have irritable bowel syndrome, which is made worse by stress. There is no evidence that CD is made worse by activity or work. As always, exercise is recommended. The causes of CD are an intensive area of research, but as yet these remain elusive.


CD can be difficult to diagnose. The average length of time between when symptoms of CD appear and when the disease is diagnosed is about seven years. This is because symptoms may be mild and overlap with those of other conditions.

Colonoscopy and upper GI endoscopy are excellent for visualising the upper and lower gastrointestinal tract. Colonoscopy can also check the last part of the small bowel for CD. If needed, the entire small bowel can be checked by capsule endoscopy. This is where a camera is swallowed and takes pictures along the entire gastrointestinal tract, from the mouth to the anus. Magnetic resonance enterography is also an excellent investigation for CD affecting the small bowel. This procedure involves the patient drinking a special fluid before they are scanned.

Blood tests are helpful for detecting complications of CD, including inflammation and malabsorption of nutrients from the diet. A faecal calprotectin test is useful for distinguishing between irritable bowel syndrome and CD.

Sometimes CD is diagnosed during surgery that is being done for something else. For example, during an operation for suspected appendicitis, it may become apparent to the surgeon that the problem is not the appendix itself but CD affecting the bowel near the appendix. The affected area can be removed surgically at that time.


Unfortunately, there is no cure for CD. However, many people can be maintained with good quality of life and in some the disease seems to disappear. Hopefully a cure can be found when we understand why CD develops in the first place. The type of treatment offered depends on the severity of symptoms and the part of the gastrointestinal tract that is affected.


There are no specific food items proven to cause CD. However, certain foods or drinks can aggravate symptoms. Some people find limiting dairy useful, others prefer low-fat foods. Some people find it helpful to eat smaller meals more often during the day and to reduce their dietary fibre. For people with CD who also have irritable bowel syndrome, it may simply be that feeling better when they avoid certain foods is more to do with their irritable bowel syndrome than their CD.


Anti-inflammatory drugs, such as mesalazine, are useful for mild symptoms of CD. For more severe symptoms, drugs such as azathioprine that suppress the immune system may be needed. Steroids are usually needed for flare-ups of CD. Long-term treatment with antibiotics, commonly metronidazole or ciprofloxacin, are helpful for infections that develop around the anus. Medications used for CD affecting the last part of the colon are often given by suppository or enema. Steroids may be given intravenously in the event of a severe flare-up of the disease. Essentially, the amount of medication given depends on the severity of the disease.


The aim of any surgery for CD is to preserve as much bowel as possible. The most common operation is removal of a segment of small bowel, but this is only done when absolutely necessary. If the colon (large bowel) is affected, some form of colectomy may be needed. Unfortunately, a total colectomy, ie, surgical removal of the entire large bowel, is sometimes the only way of treating CD.

CD can return in other areas of the bowel after surgery. One in two people who undergo surgery for CD will require further surgery in 10 years’ time, and in turn, one in two of those people will need further surgery in another 10 years, and so on. It is for this reason that we try very hard to treat CD medically and remove as little of the bowel as possible when surgery is needed.

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