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Microscopic Colitis: What Causes Microscopic Colitis & How to Treat It

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Microscopic colitis is caused by inflammation of the large intestine. It is believed to be caused by an overly aggressive immune response to certain triggers.

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What is microscopic colitis?

Microscopic colitis is caused by inflammation of the large intestine than can only be seen with a microscope. It is believed that microscopic colitis is caused by an overly aggressive immune response to a certain trigger that can be related to medication, an infection, autoimmune diseases, genetics, or a malabsorption of bile.

Symptoms primarily include watery diarrhea accompanied by abdominal pain, cramps or discomfort, and an urgency to use the restroom.

Treatment depends on the cause, such as halting offensive drugs and taking anti-diarrheal medication or steroids. It is also important to make sure you stay hydrated throughout the recovery period.

You should visit your primary care physician, who, depending on his/her exam, may recommend a biopsy to determine the diagnosis. Treatment would involve anti-inflammatory agents.

Microscopic colitis symptoms

Symptoms of microscopic colitis mainly include chronic diarrhea, fecal urgency, and abdominal discomfort.

Main symptoms

The primary symptom of microscopic colitis is chronic, watery diarrhea with an absence of blood in the stool. Because of the volume of stool frequently produced, visible blood is rare; however, a physician may find trace (e.g. small) amounts of blood during an examination. Other characteristics and associated symptoms of diarrhea include:

  • Diarrhea that is continuous or intermittent
  • Accompanying abdominal pain or cramps
  • Experience of bloating or discomfort
  • Inconsistent: Diarrhea will not have a characteristic smell, color, or consistency and this may vary between individuals and causes.
  • Mucus in the stool: This often cannot be ascertained visually.

Fecal urgency

Fecal urgency associated with microscopic colitis can be described as or associated with:

  • A very strong and sudden urge to have a bowel movement
  • A need to use the restroom immediately
  • An inability to reach the restroom in time
  • Fecal incontinence: You may experience some leaking or soiling of the clothes prior to reaching a restroom without the full feeling of urgency that usually accompanies a bowel movement.

Abdominal discomfort

Abdominal cramps or pain are commonplace in microscopic colitis and are thought to occur as the large intestine contracts and responds to persistent diarrhea. Details include:

  • Pain occurs with or without bowel movements
  • Pain improves after bowel movements
  • Nausea is common
  • Vomiting is rarer

Microscopic colitis quiz

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Causes of microscopic colitis

Inflammation is how the body normally responds to injury by either infections or some other irritant. However, the cause of inflammation in microscopic colitis varies and can be caused by many different infectious, non-infectious, and behavioral processes.

Microscopic colitis can be either collagenous, meaning a thick layer of collagen (protein) develops in the colon, or lymphocytic, meaning white blood cells (lymphocytes) increase in colon tissue. However, this distinction is less emphasized because the treatment does not differ between the two. Microscopic colitis has the same symptoms of many different causes of diarrhea but is confirmed by gut biopsy.


There is no evidence that medication can cause microscopic colitis by itself, however, there are links between many medications and the development of microscopic colitis with the addition of other diagnoses (discussed in later sections). Below is a small subset of medications thought to cause this condition, though many other drugs are also linked but not known to cause microscopic colitis, including:

  • Non-steroidal anti-inflammatories (NSAIDs): Such as ibuprofen (Advil, Motrin)
  • Proton pump inhibitors: Such as lansoprazole
  • Antidiabetic medications: Such as acarbose
  • H2 blocker antihistamines: Such as ranitidine
  • Blood thinners: Such as ticlopidine
  • SSRI antidepressants: Such as Sertraline

Bacterial/Viral infection

Bacterial infection can lead to microscopic colitis as bacteria produce toxic molecules (toxins) that damage the colon. Viral infections may also cause inflammation in the gastrointestinal tract and have a significant role in causing microscopic colitis. In both cases, there are two possible ways that microscopic colitis is caused:

  • Direct gut damage: In this setting, bacteria (e.g. Yersinia pestis) can directly damage the inner wall (e.g. lumen) of the gut and this may trigger symptoms.
  • Faulty immune attack: The bacteria or virus may also produce a toxin that is similar to either a food molecule or a naturally occurring part of the gut, causing continuous damage as the body perceives this food or organ as foreign and attacks it.

Autoimmune diseases

Autoimmune diseases cause microscopic colitis as they are triggered by a benign food product. The body treats a benign food substance as it would an infection, causing similar symptoms. Common autoimmune diseases that are often inherited include:

  • Celiac disease: The body overreacts to gluten usually found in grains or bread. Celiac disease in older women is commonly associated with microscopic colitis, but markers for celiac disease do not co-occur frequently with microscopic colitis even though it is the most commonly associated autoimmune disorder.
  • Rheumatoid Arthritis (RA)
  • Psoriasis
  • Inflammatory bowel diseases: Such as Crohn’s disease and Ulcerative Colitis
  • Thyroid disorders: Such as Grave’s disease and Hashimoto’s thyroiditis


Microscopic colitis is usually not familial or directly inherited, although, as many as 12 percent of microscopic colitis cases have a family history of inflammatory bowel disease (which may have similar symptoms). The genetic link between other inflammatory conditions and microscopic colitis is linked to a few naturally occurring compounds, most notably, certain types of the immune system marker HLA-DQ. This can lead to the inheritance of the autoimmune disease discussed above.

Bile acid malabsorption

Bile acids are the compounds that allow your water-soluble proteins in the gut to digest the fats that you consume. Bile acids combine with fat to make a substance that can be reabsorbed by the gut. The inability to completely reabsorb bile acids is associated with both lymphocytic colitis and collagenous colitis [3]. It is unclear whether bile acid malabsorption is the primary cause or a secondary characteristic of microscopic colitis. Bile acids are thought to play a role in microscopic colitis development because they are caustic, and if they are not completely reabsorbed before they reach the colon, they can lead to diarrhea.

Who is most likely to be affected

Those most likely to be diagnosed with microscopic colitis include:

  • Older individuals
  • Females: This may be because women with celiac disease outnumber men by as many as five to one
  • Those with any autoimmune disorder
  • Individuals that smoke
  • Individuals that take any of the medications mentioned above

Microscopic colitis quiz

Take a quiz to find out if you have microscopic colitis.

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Treatment options and prevention for microscopic colitis

The initial approach to the treatment of microscopic colitis is in response to the severity of the symptoms. Most people respond to some sort of medication, and surgical intervention is rare. Treatments include a discontinuation and possible substitution of offending drugs, anti-diarrheal medications, as well as steroids, if necessary.

Discontinue offending drugs

To comprehensively treat microscopic colitis, it is first necessary to identify which if any drugs are contributing to the symptoms and discontinue them. This is most commonly done in concert with a personal physician who either prescribes an alternate drug or limits the drug list of a person affected by biopsy-proven microscopic colitis.

Anti-diarrheal medication

Certain anti-diarrheal medications are used to help alleviate symptoms of microscopic colitis.

  • Types: Common antidiarrheals include bulking agents that increase the volume of stool and slow down gut motility to decrease diarrhea. Following antidiarrheals, most people are treated with bismuth agents containing bismuth salicylate.
  • Efficacy: Generally, these work quickly and are reliable — usually going to work within a few doses.


This is the most common treatment for severe microscopic colitis if it is unresponsive to previous methods.

  • Types: The steroid drug budesonide is most commonly used. Steroids, in sufficient doses, can reduce the activity of the immune system and reduce the autoimmune process that contributes to microscopic colitis.
  • Efficacy: Steroids are only used for a short period of time. Even though they are commonly effective, microscopic colitis often returns when the steroids are discontinued.


Generally, medications for microscopic colitis are trialed for as little as two weeks depending on the treatment setting. As it becomes apparent that drugs are ineffective, the physician will either move to a stronger medication or re-evaluate the original diagnosis for another diagnosis, like Celiac or Sprue, for example. In most cases, a response takes place in two weeks, though the disease may reoccur.

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When to seek further consultation for microscopic colitis

You should seek medical attention if you have lost significant weight, are severely dehydrated, or your other symptoms persist. It is also important to not ignore any symptoms as they can cause significant complications.

If you have lost significant weight

Seek further consultation if you have had precipitous weight decline over the period during which you have had microscopic colitis. Although microscopic colitis can cause weight loss, other diseases like malignancy can also cause altered bowel movements and weight loss.

If your symptoms last for more than two weeks

You should seek further consultation if you have had diarrhea for over two weeks. Most infectious causes of diarrhea self-resolve within a few weeks.

Additionally, loss of fluids can lead to dehydration which can cause fainting, and in severe cases, heart problems. If you are unable to replenish your fluids and your electrolytes, you should seek medical help.

Questions your doctor may ask to determine microscopic colitis

  • Have you lost your appetite recently?
  • Have you been feeling more tired than usual, lethargic or fatigued despite sleeping a normal amount?
  • Any fever today or during the last week?
  • Do you currently smoke?
  • Are your symptoms causing difficulty at work, socializing, or spending time with friends & family?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

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The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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  1. Microscopic colitis symptoms and causes. Mayo Clinic. Mayo Clinic Link
  2. Microscopic colitis. National Institute of Diabetes and Digestive and Kidney Diseases. Published June 2014. NIDDK Link
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  4. Celiac disease prevalence in women. Beyond Celiac Org. BCO Link
  5. Chande N. Microscopic colitis: An approach to treatment. Canadian Journal of Gastroenterology. 2008;22(8):686-688. NCBI Link
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