Ulcerative colitis is a long-term condition where the colon and rectum become inflamed.
The colon is the large intestine (bowel) and the rectum is the end of the bowel where stools are stored.
Small ulcers can develop on the colon's lining, and can bleed and produce pus.
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The main symptoms of ulcerative colitis are:
You may also experience extreme tiredness (fatigue), loss of appetite and weight loss.
The severity of the symptoms varies, depending on how much of the rectum and colon is inflamed and how severe the inflammation is.
For some people, the condition has a significant impact on their everyday lives.
Some people may go for weeks or months with very mild symptoms, or none at all (remission), followed by periods where the symptoms are particularly troublesome (flare-ups or relapses).
During a flare-up, some people with ulcerative colitis also experience symptoms elsewhere in their body.
For example, some people develop:
In severe cases, defined as having to empty your bowels 6 or more times a day, additional symptoms may include:
In most people, no specific trigger for flare-ups is identified, although a gut infection can occasionally be the cause.
Stress is also thought to be a potential factor.
You should see a GP as soon as possible if you have symptoms of ulcerative colitis and you have not been diagnosed with the condition.
They can arrange blood or stool sample tests to help determine what may be causing your symptoms.
If necessary, they can refer you to hospital for further tests.
If you have been diagnosed with ulcerative colitis and think you may be having a severe flare-up, contact a GP or your care team for advice.
You may need to be admitted to hospital.
Ulcerative colitis is thought to be an autoimmune condition.
This means the immune system, the body's defence against infection, goes wrong and attacks healthy tissue.
The most popular theory is that the immune system mistakes harmless bacteria inside the colon for a threat and attacks the tissues of the colon, causing it to become inflamed.
Exactly what causes the immune system to behave in this way is unclear.
Most experts think it's a combination of genetic and environmental factors.
It's estimated around 1 in every 420 people living in the UK has ulcerative colitis. This amounts to around 146,000 people.
The condition can develop at any age, but is most often diagnosed in people aged from 15 to 25 years old.
It's more common in white people of European descent, especially those descended from Ashkenazi Jewish communities, and black people.
The condition is rarer in people from Asian backgrounds, although the reasons for this are unclear.
Both men and women seem to be equally affected by ulcerative colitis.
Treatment for ulcerative colitis aims to relieve symptoms during a flare-up and prevent symptoms from returning (maintaining remission).
In most people, this is achieved by taking medicine, such as:
Mild to moderate flare-ups can usually be treated at home. But more severe flare-ups need to be treated in hospital.
If medicines are not effective at controlling your symptoms or your quality of life is significantly affected by your condition, surgery to remove your colon may be an option.
During surgery, your small intestine will either be diverted out of an opening in your abdomen (an ileostomy) or be used to create an internal pouch that's connected to your anus called an ileoanal pouch.
Complications of ulcerative colitis include:
Also, some of the medications used to treat ulcerative colitis can cause weakening of the bones (osteoporosis) as a side effect.
Inflammatory bowel disease (IBD) is a term mainly used to describe 2 conditions that cause inflammation of the gut (gastrointestinal tract).
IBD should not be confused with irritable bowel syndrome (IBS), which is a different condition and requires different treatment.
Our guide to care and support explains your options and where you can get support.