Patient information from BMJ

Crohn's disease: what is it?

Last published:Jun 23, 2020

Crohn's disease is a long-term condition that affects your gut. It can cause problems anywhere from your mouth to your anus (back passage). People with Crohn's disease often get diarrhoea and pain around their abdomen.

The condition can cause serious problems. Medications can help to control Crohn's disease, but many people need to have surgery at some point. 

What is Crohn's disease?

If you have Crohn's disease, you get patches of inflammation (swelling) on the wall of your gut. This can cause uncomfortable symptoms such as stomach pain. Inflammation can also block the flow of food through your gut. 

Crohn's disease can be difficult to live with and hard to predict. There might be times when your symptoms get worse, and times when you don't get any symptoms at all. 

Doctors aren't sure what causes Crohn's disease. It might be partly down to your genes. 

Inflammation in your bowel can cause serious problems if it becomes severe. You might get a blockage, or a hole in the wall of your bowel (called a perforation) These problems need urgent treatment.

A blocked bowel can cause:

• pain

• bloating

• constipation, and

• vomiting.

A hole in your bowel can:

• cause severe pain

• give you a fever, and

• make you feel generally very unwell.

What are the symptoms?

Symptoms of Crohn's disease include:

• bouts of diarrhoea (loose stools)

• losing weight without trying

• cramps or pain. Pain often affects the area around the belly button, or the lower right part of your belly

• bleeding in your bowel. You might notice bright red blood in your stools, or it might be almost black. You might see mucus or pus in the stool. If the bleeding lasts a long time, you can become anaemic. This means your blood cannot carry oxygen around the body efficiently. Anaemia can make you feel very tired.

Diagnosing Crohn's disease

Diagnosing Crohn's disease can be difficult. The symptoms vary from person to person, and some of the symptoms are the same as those caused by other illnesses.

You might need several tests, including:

• blood tests

• stool tests

• radiological tests or scans, and

• a colonoscopy, which is the only way to be sure you have Crohn's. This involves putting a tiny camera on the end of a flexible tube into your bowel, through your anus (back passage). 

What will happen to me?

There is no cure for Crohn's disease, but there are treatments that can help. To learn more, see our leaflet Crohn's disease: what treatments work?

Many people with Crohn's disease need surgery at some point. But it might be many years before you need surgery, and some people never need it. 

Crohn's disease tends to improve for people who stop smoking. If you smoke, it's a good idea to stop.

You will need check-ups with your doctor every few months. You may also have tests every so often to check for more serious illnesses, such as bowel cancer. 

You should talk to your doctor whenever your symptoms get worse. There may be times when you need urgent medical help.

See a doctor as soon as you can if you:

• have a fever

• have severe pain

• have blood in your stools

• have bloating

• feel dizzy, or

• feel dehydrated.

It's also important to get help quickly if you:

• can't go to the toilet

• can't stop being sick, or

• have fluid leaking from your anus or from anywhere on your skin.