The walls of your bowel have layers. In Microscopic Colitis the inner lining becomes inflamed. But this change can only be seen when a sample of tissue (biopsy) is taken from your colon and looked at under a microscope.  

There are two types of Microscopic Colitis: 

• Lymphocytic colitis (LC) – where the inner lining has more white blood cells (lymphocytes) than usual.
• Collagenous colitis (CC) – where the inner lining has a thicker layer of a collagen, a protein important in providing structure in the body, than usual. There may also be more white blood cells present.

Microscopic Colitis is the umbrella term for both LC and CC. Although they look different under the microscope, symptoms and treatment are the same. However slightly more people have LC, and women are more likely to have CC . Some people may even have both types of Microscopic Colitis, but at different times. 

The diarrhoea may:

• be sudden – you may not always reach the toilet in time 
• be explosive - this is when your rectum has more watery poo and gas than it can hold and it expels the poo with lots of force, often loudly
• happen several times a day and at night.

There usually isn’t any blood in the poo.

Other symptoms can include:

• pain in the tummy area – which may be cramping or dull
• fatigue or extreme tiredness – this may be caused by getting up at night to go to the toilet, but many people experience this even if they sleep through the night
• joint pain
• bloating and wind
• weight loss. 

These include:

• Damage to the lining of the gut – this may be by caused by viruses, bacteria or certain medicines.
• Genes a person has inherited. 
• Other factors such as smoking, age and gender. 

• Are over 50 years old. Most people get Microscopic Colitis when they are aged between 50 and 60.  But 1 in 4 are under 25 and children have also been diagnosed with the condition. 
• Are female
• Have an autoimmune condition (see below) 
• Smoke cigarettes
• Use certain medicines, see the list in the section Treatments for Microscopic Colitis.  

At least 1 in 1000 people are thought to have Microscopic Colitis in the UK, but the real number could be a lot higher because it’s often underreported and misdiagnosed. It’s less well known by both health professionals and the general public which may mean many people with Microscopic Colitis are coping in silence.

These include: 

• Type 1 diabetes
• thyroid disease
• coeliac disease
• rheumatoid arthritis

Bile acid malabsorption (BAM)

Around 4 out of 10 people with microscopic colitis also have BAM.  Bile salts help you to digest fats. When you eat a meal, especially with fat in it, these bile salts are released from your liver and gall bladder into the upper part of your gut. They help to digest the food as it travels through your small bowel. When the bile salts reach the far end of this, they are mostly absorbed back into your body and return to your liver in the bloodstream.

Bile acid malabsorption happens when the gut can’t direct bile acid back to the liver. It’s thought that this irritates the lining of the colon and means that your body doesn't absorb water properly. This means you produce large amounts of watery poo. Find out more in Diarrhoea and Constipation.  

In a colonoscopy, a long flexible tube (about the thickness of your little finger) with a bright light and camera at its tip is inserted through the anus, allowing the specialist to examine the lining of the colon. During the investigation, the specialist will painlessly remove small pieces of tissue from the lining of the colon, to examine in the laboratory under a microscope.

The doctor won’t be able to see any visible signs of inflammation when they look at your colon and rectum. This is different from Crohn’s or Ulcerative Colitis when inflammation or ulcers can be seen. Find out more in Tests and investigations.

Medicines that may trigger Microscopic Colitis include:  

• non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, diclofenac
• some proton pump inhibitors (PPIs) such as omeprazole and lansoprazole used to reduce stomach acid
• selective serotonin reuptake inhibitors (SSRIs) used to treat depression
• aspirin
• acarbose for diabetes
• ranitidine for indigestion and heart burn
• ticlopidine for blood conditions
• statins for cholesterol control.

Many of these medicines can also cause diarrhoea as a side effect. But if you're taking any of these do not stop taking them until you’ve talked to your doctor. 

Lifestyle changes

Cutting down alcohol and caffeine can be helpful in reducing diarrhoea. It’s often useful to keep a record of when you stop or cut down and how your symptoms change, such as in the food diary in Food.

• Try cutting down on caffeine – drink decaffeinated tea, coffee, soft drinks or water and reduce the amount of chocolate you eat.
• Cut down alcohol – drinking less has been shown to help symptoms.
• Stop smoking - smoking increases the risk of Microscopic Colitis, and people who smoke have symptoms which are worse and less likely to get better with treatment. Your GP practice can offer support with stopping smoking.  

Medicines

There may be several options for treatment depending on the severity of the symptoms you have.

• Loperamide. If you have mild Microscopic Colitis, medicines to stop diarrhoea, such as loperamide, can be effective. These slow down muscle contractions of the gut which makes food move through more slowly and allows more water to be absorbed. Poo becomes firmer and less urgent. They can also help to control symptoms whilst other medications take time to work. Find out more in our information on diarrhoea and constipation.
   
• Bile Acid Sequestrants. These include colestyramine, colestipol or colesevelam. If Microscopic Colitis is related to bile acid malabsorption (BAM), or you continue to have diarrhoea despite other treatment, you may be offered this type of medicine.  These bind to the bile acids in your gut and help to improve symptoms of diarrhoea. It has been suggested that this may be effective even where BAM isn’t present. 
   
• Budesonide. This steroid has been found to be an effective treatment if you have moderate to severe Microscopic Colitis. Around 8 out of 10 people have been shown to improve when taking this medicine and there are usually few side effects. 
  
  The normal dose is 9mg of budesonide a day for 6 to 8 weeks. You may also be offered loperamide to control the diarrhoea whilst the budesonide gets your condition under control. Your symptoms may start to get better within one or two days but for some people it can take around three to six weeks. 
  
  Over half of people on budesonide find their symptoms come back when the treatment stops. If this happens to you a lower dose may be tried, and this could be continued for up to a year. As with all steroids this isn’t usually a long-term option. Find out more in Steroids.​

Most people get better with these approaches but if they don’t work for you other treatments may be tried.

• Biologic Medicines. Infliximab and adalimumab have been shown in small studies to improve symptoms for some people where budesonide hasn’t been effective. Small studies also suggest that vedolizumab could be helpful. These medicines are taken by infusion or injection and you can find out more in our information on biologic medicines.
   
• Immunosuppressants. Azathioprine and mercaptopurine have been shown to be effective for some people where budesonide hasn’t worked. Find out more in Azathioprine and mercaptopurine.

Surgery

Surgery is very rarely needed, but for the few people where other approaches haven’t been successful this can be an option. You can find out more about possible operations in Surgery for Ulcerative Colitis. 

Many people ask: 

Should I avoid gluten? - People with Microscopic Colitis are more than 50 times more likely than the general population to have coeliac disease. This means you’re not able to digest a type of protein called gluten, which is found in wheat, barley and rye. To find out if you need to avoid gluten, your doctor will do a blood test to check for this. If your blood test is positive, you may also have an upper gastrointestinal endoscopy to confirm. Find out more in​ Food and Tests and investigations.
 

Should I avoid dairy products? – If your diarrhoea is worse after eating dairy, you may have trouble digesting lactose - the type of sugar found mainly in milk, cheese and other dairy products. Keeping a food diary to see how you feel can help you to find out if this is the case for you – try the one in Food. Sometimes a simple breath test is used to find out if you’re lactose intolerant.

Talk to your doctor or dietitian before making any major changes to your diet. They can help you plan how to avoid dairy products or gluten while still getting the nutrients you need.

An IBD nurse can offer support and advice about treatment options, daily life with Microscopic Colitis and help you to live well with IBD. But NHS support services vary - some areas still don’t have an IBD nurse, whilst others have limited resources and may not be able to support you if you have Microscopic Colitis.

Find out if your hospital has an IBD nurse.