Microscopic colitis is a chronic gut condition. It’s a type of inflammatory bowel disease (IBD) that affects your colon, and it causes frequent, watery diarrhoea that doesn’t contain blood.
This condition can be tricky to diagnose, and managing the symptoms often requires long-term treatment.
There’s evidence that microscopic colitis is behind 12.8% of cases of unexplained, chronic, watery diarrhoea.
It mainly affects older adults – only a quarter of people with the diagnosis receive it before they turn 45. Microscopic colitis also occurs more often in females than males.
Doctors typically can’t see the telltale changes to the colon before they examine a tissue sample. This is what gives microscopic colitis its name. It’s also the reason why this condition can go undiagnosed.
In this article, we take a look at the symptoms and what can trigger them. We’ll also describe how doctors diagnose microscopic colitis – and what you can do to help treat it.
Symptoms
Here’s a list of microscopic colitis symptoms you may experience:
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non-bloody, watery diarrhoea
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the sudden need to poo
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being unable to control when you poo
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pooing during the night
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abdominal cramps, bloating and wind
For most people with microscopic colitis, the diarrhoea comes and goes. Some people with the condition have also reported:
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weight loss
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joint pain
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tiredness
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nausea
Research suggests that in 42% of microscopic colitis cases, the symptoms can appear suddenly.
Learn what’s normal when it comes to diarrhoea.
Causes
Experts have yet to discover why microscopic colitis occurs. Some say that it likely stems from a combination of factors.
Like other forms of IBD, microscopic colitis develops when your immune system attacks your digestive tract. This causes inflammation in your colon.
Some factors that could play a role include:
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certain genes
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changes in how your body processes collagen, a protein
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changes in how your immune system works
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coeliac disease
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bile acid malabsorption, which leads to higher levels of bile in your colon
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an autoimmune condition, such as diabetes or rheumatoid arthritis
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smoking
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having a Westernised dietary pattern
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being female
Some researchers are investigating whether taking certain medications causes some people to develop microscopic colitis.
While more evidence is needed, existing studies suggest that the following classes of drugs may be involved:
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NSAIDs
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proton pump inhibitors, also known as PPIs
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selective serotonin reuptake inhibitors, also known as SSRIs
Types
The two main types of microscopic colitis are distinguished by different changes in the colon’s lining. They are:
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Lymphocytic colitis: There’s an increased number of white blood cells.
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Collagenous colitis: With this type, there’s an increased amount of collagen.
These types cause the same symptoms, and doctors treat them in the same way.
Microscopic colitis vs other IBDs
Microscopic colitis is a form of IBD. Some other forms are Crohn’s disease and ulcerative colitis.
All three affect your gut in a similar way, leading to inflammation and symptoms like diarrhoea, changes in your poo and abdominal pain.
One main difference between microscopic colitis and these other types of IBD involves the way your colon looks during a colonoscopy. This procedure involves inserting a thin tube with a camera into your digestive tract.
When someone has Crohn’s disease or ulcerative colitis, the doctor can see distinct signs during a colonoscopy. In someone with microscopic colitis, the colon usually appears normal.
The other main difference is that blood may appear in your poo if you have Crohn’s disease or ulcerative colitis, but not if you have microscopic colitis.
Learn more about what your poo can tell you about your gut health.
Diagnosis
To diagnose microscopic colitis, the main thing that a doctor needs is a tissue sample from your colon. They typically collect this during a colonoscopy.
Doctors can also run a number of tests on blood and poo samples to rule out other conditions that might be causing your symptoms.
When they analyse the tissue sample, they can assess the levels of collagen and white blood cells in the colon’s lining. This can help them determine the type of microscopic colitis.
Learn why IBD is different from irritable bowel syndrome.
Treatment
The aim of treating microscopic colitis is for you to have fewer than three poos a day, none of which are watery. The approach to treatment will depend on how severe your symptoms are.
For most people, the main course of treatment is a medication called budesonide, which is a steroid. You’ll take this by mouth for 6–8 weeks.
Your doctor may suggest alternatives to budesonide, such as the anti-diarrhoea medication loperamide. This can help reduce how often people poo during the night.
They might also recommend other drugs, like immunosuppressants or bile acid sequestrants, such as colestyramine or colesevelam.
If medication doesn’t improve things, the doctor may consider surgery as a final step. This could involve creating a hole so that food can leave your body without passing through the colon (an ileostomy) or removing part or all of the colon (a colectomy).
To help the treatment, the doctor will also advise you to stop smoking and taking any medication that might be linked to microscopic colitis. It’s important to follow the doctor’s guidance about how to end a course of medication.
Whenever you’re experiencing diarrhoea, you should drink lots of fluids to prevent dehydration.
Outlook
Microscopic colitis sometimes goes away on its own, though most cases require treatment.
Medications are generally quite effective. But the symptoms eventually come back in 60–80% of cases.
The likelihood of this condition returning after treatment may depend on the type. Some evidence shows that recovery is more common among people with lymphocytic colitis.
If your symptoms return, the doctor may recommend a smaller dosage of budesonide to manage them.
Microscopic colitis rarely leads to serious complications. But the impact it can have on your day-to-day life means that seeking treatment is important.
It’s also worth noting that researchers have found no link between having microscopic colitis and going on to develop colorectal cancer, ulcerative colitis or Crohn’s disease.
Summary
Microscopic colitis is a form of IBD that gives you frequent bouts of watery diarrhoea.
Experts aren’t entirely sure what causes this condition. A doctor can usually only diagnose it by examining a sample of tissue from your colon.
Medication often brings microscopic colitis under control. This means reducing your number of poos until they’re unlikely to interfere with your daily routine.
To learn more about other gut health topics, visit Symprove’s Gut Hub.
Sources
Crohn’s disease. (2021). Link.
Diarrhoea and vomiting. (2023). Link.
Diet, food, and nutritional exposures and inflammatory bowel disease or progression of disease: An umbrella review. Advances in Nutrition. (2024). Link.
European guidelines on microscopic colitis: United European Gastroenterology and European Microscopic Colitis Group statements and recommendations. United European Gastroenterology Journal. (2021). Link.
Inflammatory bowel disease. (2023). Link.
Microscopic colitis. BMJ Best Practice. (2024). Link.
Microscopic colitis: A guide for general practice. British Journal of General Practice. (2021). Link.
Microscopic colitis: An update. Medicine and Pharmacy Reports. (2022). Link.
Microscopic colitis: Diagnosis and management. Frontline Gastroenterology. (2018). Link.
Ulcerative colitis. (2022). Link.
