The exact cause of ulcerative colitis is unknown, although it's thought to be the result of a problem with the immune system.

Autoimmune condition

The immune system is the body's defence against infection. Many experts believe ulcerative colitis is an autoimmune condition (when the immune system mistakenly attacks healthy tissue).

The immune system normally fights off infections by releasing white blood cells into the blood to destroy the cause of the infection.

This results in swelling and redness (inflammation) of body tissue in the infected area.

In ulcerative colitis, a leading theory is that the immune system mistakes "friendly bacteria" in the colon, which aid digestion, as a harmful infection, leading to the colon and rectum becoming inflamed.

Alternatively, some researchers believe a viral or bacterial infection triggers the immune system, but for some reason it does not "turn off" once the infection has passed and continues to cause inflammation.

It's also been suggested that no infection is involved and the immune system may just malfunction by itself, or that there's an imbalance between good and bad bacteria within the bowel.

Genetics

It also seems inherited genes are a factor in the development of ulcerative colitis.

Studies have found more than 1 in 4 people with ulcerative colitis has a family history of the condition.

Levels of ulcerative colitis are also a lot higher in certain ethnic groups, further suggesting that genetics are a factor.

Researchers have identified several genes that seem to make people more likely to develop ulcerative colitis.

It's believed many of these genes play a role in the immune system.

Environmental factors

Where and how you live also seems to affect your chances of developing ulcerative colitis, which suggests environmental factors are important.

For example, the condition is more common in urban areas of northern parts of western Europe and America.

Various environmental factors that may be linked to ulcerative colitis have been studied, including air pollution, medication and certain diets.

Although no factors have so far been identified, countries with improved sanitation seem to have a higher population of people with the condition.

This suggests that reduced exposure to bacteria may be an important factor.

To diagnose ulcerative colitis, your GP will first ask about your symptoms, general health and medical history.

They'll also physically examine you, checking for signs such as paleness (caused by anaemia) and tenderness in your tummy (caused by inflammation).

A stool sample can be checked for signs of infection, as gastroenteritis (infection of the stomach and bowel) can sometimes have similar symptoms to ulcerative colitis.

Blood tests may also be carried out to check for anaemia and to see if there's inflammation on any part of your body.

Further tests

If your GP suspects you may have inflammatory bowel disease (IBD) (a term mainly used to describe 2 diseases: ulcerative colitis or Crohn's disease), you may be referred to hospital for further tests.

These could include an X-ray or CT scan to rule out serious complications and a detailed examination of your rectum and colon.

Sigmoidoscopy

A diagnosis of ulcerative colitis can be confirmed by examining the level and extent of bowel inflammation.

This is initially done by using a sigmoidoscope, a thin, flexible tube containing a camera that's inserted into your rectum (bottom).

A sigmoidoscopy can also be used to remove a small sample of tissue from your bowel so it can be tested in a laboratory. This is known as a biopsy.

The procedure can be uncomfortable and you can be given a sedative to help you relax.

It usually takes around 15 minutes and you can often go home the same day.

During this procedure, only the rectum and lower part of the colon are examined.

If it's thought your ulcerative colitis has affected more of your colon, another examination will be required. This is known as a colonoscopy.

Colonoscopy

A colonoscopy uses a flexible tube containing a camera called a colonoscope, which allows your entire colon to be examined. A biopsy sample can also be taken.

Before having a colonoscopy, your colon needs to be completely empty, so you'll need to take strong laxatives beforehand.

A colonoscopy can be uncomfortable, but you'll be given sedatives and pain medications to help you relax and make the procedure as painless as possible.

The procedure takes around half an hour and you'll be able to go home the same day.

Treatment for ulcerative colitis depends on how severe the condition is and how often your symptoms flare-up.

The main aims of treatment are to:

• reduce symptoms, known as inducing remission (a period without symptoms)
• maintain remission

This usually involves taking various types of medicine, although surgery may sometimes be an option.

Your treatment will normally be provided by a range of healthcare professionals, including:

• specialist doctors, such as gastroenterologists or surgeons
• GPs
• specialist nurses

Your care will often be co-ordinated by your specialist nurse and your care team, and they'll usually be your main point of contact if you need help and advice.

Aminosalicylates

Aminosalicylates, also known as 5-ASAs, are medicines that help to reduce inflammation. This in turn allows damaged tissue to heal.

They're usually the first treatment option for mild or moderate ulcerative colitis.

5-ASAs can be used as a short-term treatment for flare-ups. They can also be taken long term, usually for the rest of your life, to maintain remission.

5-ASAs can be taken:

• orally – by swallowing a tablet or capsule
• as a suppository – a capsule that you insert into your bottom (rectum), where it dissolves
• through an enema – where fluid is pumped into your large intestine

How you take 5-ASAs depends on the severity and extent of your condition.

If you have mild-to-moderate ulcerative colitis, you'll usually be offered a 5-ASA to take in suppository or enema form.

If your symptoms do not improve after 4 weeks, you may be advised to take 5-ASA in tablet or capsule form as well.

These medicines rarely have side effects, but some people may experience:

• headaches
• feeling sick
• tummy pain
• a rash
• rarely, diarrhoea

Corticosteroids

Corticosteroids, such as prednisolone, are a more powerful type of medicine used to reduce inflammation.

They can be used with or instead of 5-ASAs to treat a flare-up if 5-ASAs alone are not effective.

Like 5-ASAs, steroids can be administered orally, or through a suppository or enema.

But unlike 5-ASAs, corticosteroids are not used as a long-term treatment to maintain remission because they can cause potentially serious side effects, such as weakening of the bones (osteoporosis) and cloudy patches in the lens of the eye (cataracts), when used for a long time.

Side effects of short-term steroid use can include:

• acne
• weight gain
• increased appetite
• mood changes, such as becoming more irritable
• difficulty sleeping (insomnia) 

Find out more about the side effects of corticosteroids

Immunosuppressants

Immunosuppressants, such as tacrolimus and azathioprine, are medicines that reduce the activity of the immune system.

They're usually given as tablets to treat mild or moderate flare-ups, or maintain remission if your symptoms have not responded to other medicines.

Immunosuppressants can be very effective in treating ulcerative colitis, but they often take a while to start working (usually between 2 and 3 months).

The medicines can make you more vulnerable to infection, so it's important to report any signs of infection, such as a high temperature or sickness, promptly to a GP.

They can also lower the production of red blood cells, making you prone to anaemia.

You'll need regular blood tests to monitor your blood cell levels and check for any other problems.

Treating severe flare-ups

While mild or moderate flare-ups can usually be treated at home, more severe flare-ups should be managed in hospital to minimise the risk of dehydration and potentially fatal complications, such as your colon rupturing.

In hospital, you'll be given medicine and sometimes fluids directly into a vein (intravenously).

The medicines you have will usually be a type of corticosteroid or an immunosuppressant medicine called infliximab or ciclosporin.

Ciclosporin

Ciclosporin works in the same way as other immunosuppressant medicines by reducing the activity of the immune system.

But it's more powerful than the medicines used to treat milder cases of ulcerative colitis and starts to work much sooner (normally within a few days).

Ciclosporin is given slowly through a drip in your arm (an infusion) and treatment will usually be continuous, for around 7 days.

Side effects of intravenous ciclosporin can include:

• an uncontrollable shaking or trembling of part of the body (a tremor) 
• excessive hair growth
• extreme tiredness (fatigue)
• swollen gums
• feeling and being sick
• diarrhoea

Ciclosporin can also cause more serious problems, such as high blood pressure and reduced kidney and liver function, but you'll be monitored regularly during treatment to check for signs of these.

Biologic medicines

Infliximab, adalimumab, golimumab and vedolizumab are medicines that reduce inflammation of the intestine by targeting proteins the immune system uses to stimulate inflammation.

These medicines block these receptors and reduce inflammation.

They may be used to treat adults with moderate to severe ulcerative colitis if other options are not suitable or working.

Infliximab may also be used to treat children or young people aged 6 to 17 with severe ulcerative colitis.

The treatment is given for 12 months unless the medicine is not working well.

Read the full NICE guidelines on:

• infliximab, adalimumab and golimumab for treating moderately to severely active ulcerative colitis after the failure of conventional therapy
• vedolizumab for treating moderately to severely active ulcerative colitis

Infliximab

Infliximab is given as an infusion over the course of 1 to 2 hours. You'll be given further infusions after 2 weeks, and again after 6 weeks.

Infusions are then given every 8 weeks if treatment is still required.

Common side effects of infliximab can include:

• increased risk of infection – report any symptoms of a possible infection, such as coughs, a high temperature or a sore throat, to a GP
• the sensation that you or the environment around you is moving (vertigo) and dizziness
• an allergy-like reaction, causing breathing difficulties, hives and headaches

In most cases, a reaction to the medicine occurs in the first 2 hours after the infusion has finished.

But some people experience delayed reactions days, or even weeks, after an infusion.

If you begin to experience the symptoms listed above after having infliximab, seek immediate medical assistance.

You'll be carefully monitored after your first infusion and, if necessary, powerful anti-allergy medicine, such as epinephrine, may be used.

Infliximab is not usually suitable for people with a history of tuberculosis (TB) or hepatitis B and needs to be used with caution in people with HIV or hepatitis C.

This is because there have been a number of cases where infliximab has reactivated dormant infections. 

The medicine is also not recommended for people with a history of heart disease or multiple sclerosis.

Tofacitinib

Tofacitinib is a newer type of medicine for ulcerative colitis.

It also works by targeting the immune system, but does this in a different way from other medicines.

The tablets are recommended for people with moderate to severe ulcerative colitis if standard treatments or biologics have not worked or are not suitable.

Tofacitinib is not recommended for use in pregnancy. Women should use reliable contraception when taking it, and for at least 4 weeks after finishing the course.

Surgery

If you have frequent flare-ups that have a significant effect on your quality of life, or you have a particularly severe flare-up that's not responding to medicines, surgery may be an option.

Surgery for ulcerative colitis involves permanently removing the colon (a colectomy).

Once your colon is removed, your small intestine will be used to pass waste products out of your body instead of your colon.

This can be achieved by creating:

• an ileostomy – where the small intestine is diverted out of a hole made in your tummy; special bags are placed over this opening to collect waste materials after the operation
• an ileoanal pouch (also known as a J-pouch) – where part of the small intestine is used to create an internal pouch that's then connected to your anus, allowing you to poo normally

Ileoanal pouches are increasingly used because an external bag to collect waste products is not required.

As the colon is removed, ulcerative colitis cannot come back again after surgery.

But it's important to consider the risks of surgery and the impact of having a permanent ileostomy or ileoanal pouch.

Find out more about ileostomies and ileoanal pouches

Help and support

Living with a condition like ulcerative colitis, especially if your symptoms are severe, can be a frustrating and isolating experience.

Talking to others with the condition can provide support and comfort.

Crohn's and Colitis UK provides information on where you can find help and support.

There are a few things you can do to help keep symptoms of ulcerative colitis under control and reduce your risk of complications.

Dietary advice

Although a specific diet is not thought to play a role in causing ulcerative colitis, some changes to your diet can help control the condition.

For example, you may find it useful to:

• eat small meals – eating 5 or 6 smaller meals a day, rather than 3 main meals, may help control your symptoms
• drink plenty of fluids – it's easy to become dehydrated when you have ulcerative colitis, as you can lose a lot of fluid through diarrhoea; water is the best source of fluids, and you should avoid caffeine and alcohol, as these will make your diarrhoea worse, and fizzy drinks, which can cause flatulence (gas)
• take food supplements – ask your GP or gastroenterologist if you need food supplements, as you might not be getting enough vitamins and minerals in your diet

Keep a food diary

Keeping a food diary that documents what you eat can also be helpful. 

You may find you can tolerate some foods while others make your symptoms worse.

By keeping a record of what and when you eat, you should be able to identify problem foods and eliminate them from your diet.

But you should not eliminate entire food groups (such as dairy products) from your diet without speaking to your care team, as you may not get enough of certain vitamins and minerals.

If you want to try a new food, it's best to only try 1 type a day because it's then easier to spot foods that cause problems.

Low-residue diet

Temporarily eating a low-residue or low-fibre diet can sometimes help improve symptoms of ulcerative colitis during a flare-up.

These diets are designed to reduce the amount and frequency of the stools you pass.

Examples of foods that can be eaten as part of a low-residue diet include:

• white bread
• refined (non-wholegrain) breakfast cereals, such as cornflakes
• white rice, refined (low-fibre) pasta and noodles
• cooked vegetables (but not the peel, seeds or stalks)
• lean meat and fish
• eggs

If you're considering trying a low-residue diet, make sure you talk to your care team first.

Stress relief

Although stress does not cause ulcerative colitis, successfully managing stress levels may reduce the frequency of symptoms.

The following advice may help:

• exercise – this has been proven to reduce stress and boost your mood; your GP or care team can advise on a suitable exercise plan
• relaxation techniques – breathing exercises, meditation and yoga are good ways of teaching yourself to relax
• communication – living with ulcerative colitis can be frustrating and isolating; talking to others with the condition can help

For more information and advice, see:

• exercise to relieve stress
• relaxation tips

Emotional impact

Living with a long-term condition that's as unpredictable and potentially debilitating as ulcerative colitis can have a significant emotional impact.

In some cases, anxiety and stress caused by ulcerative colitis can lead to depression.

Signs of depression include feeling very down, hopeless and no longer taking pleasure in activities you used to enjoy.

If you think you might be depressed, contact your GP for advice.

You may also find it useful to talk to others affected by ulcerative colitis, either face-to-face or via the internet.

Crohn's and Colitis UK is a good resource, with details of local support groups and a large range of useful information on ulcerative colitis and related issues.

Fertility

The chances of a woman with ulcerative colitis becoming pregnant are not usually affected by the condition.

But infertility can be a complication of surgery carried out to create an ileo-anal pouch.

This risk is much lower if you have surgery to divert the small intestine through an opening in your abdomen (an ileostomy).

Pregnancy

The majority of women with ulcerative colitis who decide to have children will have a normal pregnancy and a healthy baby.

But if you're pregnant or planning a pregnancy, you should discuss it with your care team.

If you become pregnant during a flare-up or have a flare-up while pregnant, there's a risk you could give birth early (premature birth) or have a baby with a low birthweight.

For this reason, doctors usually recommend trying to get ulcerative colitis under control before getting pregnant.

Most ulcerative colitis medications can be taken during pregnancy, including corticosteroids, most 5-ASAs and some types of immunosuppressant medication.

But there are certain medications, such as some types of immunosuppressant, that may need to be avoided as they're associated with an increased risk of birth defects.

In some cases, your doctors may advise you to take a medicine that's not normally recommended during pregnancy.

This might happen if they think the risks of having a flare-up outweigh the risks associated with the medicine.

If you have ulcerative colitis, you could develop further problems.

Osteoporosis

People with ulcerative colitis are at an increased risk of developing osteoporosis, when the bones become weak and are more likely to fracture.

This is not directly caused by ulcerative colitis, but can develop as a side effect of the prolonged use of corticosteroid medication.

It can also be caused by the dietary changes someone with the condition may take, such as avoiding dairy products, if they believe it could be triggering their symptoms.

If you're thought to be at risk of osteoporosis, the health of your bones will be regularly monitored.

You may also be advised to take medication or supplements of vitamin D and calcium to strengthen your bones.

Find out more about treating osteoporosis

Poor growth and development

Ulcerative colitis, and some of the treatments for it, can affect growth and delay puberty.

Children and young people with ulcerative colitis should have their height and body weight measured regularly by healthcare professionals.

This should be checked against average measurements for their age.

These checks should be carried out every 3 to 12 months, depending on the person's age, the treatment they're having and the severity of their symptoms.

If there are problems with your child's growth or development, they may be referred to a paediatrician (a specialist in treating children and young people).

Primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC), where the bile ducts become progressively inflamed and damaged over time, is a rare complication of ulcerative colitis.

Bile ducts are small tubes used to transport bile (digestive juice) out of the liver and into the digestive system.

PSC does not usually cause symptoms until it's at an advanced stage.

Symptoms can include:

• fatigue (extreme tiredness)
• diarrhoea 
• itchy skin
• weight loss
• chills
• a high temperature (fever)
• yellowing of the skin and the whites of the eyes (jaundice)

There's currently no specific treatment for PSC, although medications can be used to relieve some of the symptoms, such as itchy skin.

In more severe cases, a liver transplant may be required.

Toxic megacolon

Toxic megacolon is a rare and serious complication of severe ulcerative colitis where inflammation in the colon causes gas to become trapped, resulting in the colon becoming enlarged and swollen.

This is potentially very dangerous as it can cause the colon to rupture (split) and cause infection in the blood (septicaemia).

The symptoms of a toxic megacolon include:

• tummy pain
• a high temperature (fever)
• a rapid heart rate

Toxic megacolon can be treated with fluids, antibiotics and steroids given directly into a vein (intravenously).

If medications do not improve the conditions quickly, surgical removal of the colon (a colectomy) may be needed.

Treating symptoms of ulcerative colitis before they become severe can help prevent toxic megacolon.

Bowel cancer

People who have ulcerative colitis have an increased risk of developing bowel cancer (cancer of the colon, rectum or bowel), especially if the condition is severe or involves most of the colon.

The longer you have ulcerative colitis, the greater the risk.

People with ulcerative colitis are often unaware they have bowel cancer as the initial symptoms of this type of cancer are similar.

These include:

• blood in the stools
• diarrhoea
• abdominal pain

You'll usually have regular check-ups to look for signs of bowel cancer from about 10 years after your symptoms first develop.

Check-ups will involve examining your bowel with a colonoscope (a long, flexible tube containing a camera) that's inserted into your rectum – this is called a colonoscopy.

The frequency of the colonoscopy examinations will increase the longer you live with the condition, and will also depend on factors such as how severe your ulcerative colitis is and if you have a family history of bowel cancer.

This can vary between every 1 to 5 years.

To reduce the risk of bowel cancer, it's important to:

• eat a healthy, balanced diet including plenty of fresh fruit and vegetables
• take regular exercise
• maintain a healthy weight
• avoid alcohol and smoking

Taking aminosalicylates as prescribed can also help reduce your risk of bowel cancer.

Find out more about preventing bowel cancer