Last updated: February 2020
In addition to ulcerative colitis and Crohn’s disease, there are other less common forms of inflammatory bowel disease (IBD), including microscopic colitis.
What is microscopic colitis?
Like ulcerative colitis, microscopic colitis is inflammation of the colon (large intestine), although it can present with different symptoms than ulcerative colitis. Microscopic colitis gets its name from the fact that in order to diagnose it, an individual’s tissue sample needs to be looked at under a microscope. An individual with microscopic colitis may have a normal or healthy-looking colonoscopy before further investigation.1
There are two main types of microscopic colitis: lymphocytic colitis and collagenous colitis. Lymphocytic colitis is when there are an increased number of lymphocytes (a type of white blood cell) in the tissue of the large intestine. Collagenous colitis is characterized by the protein collagen building up in the tissue of the large intestine and thickening the colon wall. Although these two types of microscopic colitis exist, they can occur simultaneously in an individual. This has led some experts to believe that lymphocytic colitis and collagenous colitis should not be considered separate categories, but rather, two features of the same overall condition (microscopic colitis).2-4
What are the symptoms of microscopic colitis?
Symptoms of microscopic colitis can be very similar to other inflammatory bowel diseases, including abdominal pain or cramping and unexpected weight loss. However, a distinctive symptom of microscopic colitis is chronic, non-bloody, watery diarrhea. Other changes in bowel patterns may include fecal incontinence or a need to go to the bathroom urgently. Microscopic colitis may also have accompanying nausea or dehydration.3
What causes microscopic colitis?
Similar to other inflammatory bowel diseases, the exact cause of microscopic colitis is unknown. Many experts agree that a complex interaction between genetics, the bacterial composition of the digestive tract, environmental factors, and the immune system can lead to IBD. More specifically, it is often thought that the inflammation is due directly to the body’s immune system mistakenly attacking itself and the cells that line the gastrointestinal tract.5,6 Other proposed causes of microscopic colitis are bacterial infections, viral infections, and bile acid malabsorption. Bile acid helps our body break down fats and is made by the liver. If bile acid does not get reabsorbed back into the body before it reaches the colon, it can cause diarrhea.3
Although medications do not cause microscopic colitis, several medications have been linked to the condition, including non-steroidal anti-inflammatory drugs (aspirin, ibuprofen), sertraline (Zoloft), ranitidine (Zantac, Tritec), esomeprazole (Nexium), and more. Your doctor may be able to help you determine if any of the medications you take could be contributing to symptoms of microscopic colitis. Certain autoimmune conditions have also been associated with microscopic colitis, including celiac disease, Hashimoto’s disease, Graves’ disease, rheumatoid arthritis, and psoriasis.3
How is microscopic colitis diagnosed?
Similar to other inflammatory bowel diseases, diagnosis of microscopic colitis begins with an examination and personal medical history investigation by your healthcare provider. If your doctor thinks you may have an inflammatory bowel disease they may recommend taking a scope of your digestive tract by inserting a long, thin tube with a camera and light attached into the body. This may be done through the mouth (upper endoscopy) or through the rectum (colonoscopy). During the scope, they will perform a biopsy where a small sample of tissue will be taken and analyzed. The key feature of microscopic colitis is that evidence will be found after analyzing these tissues microscopically. If your doctor finds evidence of microscopic colitis, including increased lymphocytes or collagen-related thickening of the intestinal wall, you may be diagnosed with the condition.1,3
How is microscopic colitis treated?
Treatment of microscopic colitis depends on an individual’s symptoms, past medical conditions, other co-occurring conditions, and current medications taken. Common treatment options for microscopic colitis include:
- Antidiarrheal medications
- Anti-inflammatory medications
- Medications that block bile acids
- Immune system-suppressing medications
- Biologic therapies
- Changes in diet and nutrition
- Surgery (in very rare cases)3