September 4, 2015
Microscopic colitis is inflammation of the bowel that is only visible using a microscope. Microscopic colitis is a type of inflammatory bowel disease (IBD), which refers to a group of conditions that causes inflammation in the bowel due to an excessive build-up of white blood cells in the bowel lining. Microscopic colitis is less severe than other types of IBD because it does not cause bleeding or significant pain, does not increase cancer risk and does not requires surgery or cause complications. However, microscopic colitis can cause considerable chronic diarrhea and impact quality of life substantially until diagnosed and treated.
Forms of Microscopic Colitis
Microscopic colitis has two main forms: collagenous colitis and lymphocytic colitis. The symptoms of and treatment for both are identical. Most researchers believe the two forms may be different presentations of the same disease. Slight differences in the way intestinal tissues appear when seen with a microscope set them apart. In both forms, an increase in white blood cells can be seen within the intestinal inner lining. Increased white blood cells are a sign of inflammation. But with collagenous colitis, the layer of collagen beneath the lining appears thicker than normal. Collagen is a structural protein in bones and cartilage. In the intestines, collagen anchors the intestinal lining to underlying layers of tissue. The thicker collagen layer seen with collagenous colitis may result from inflammation.
The cause of microscopic colitis is unknown. Many scientists believe it is an abnormal immune response triggered by something in the gastrointestinal (GI) tract—the large, muscular tube that extends from the mouth to the anus and digests food. Normally, the immune system is triggered by germs, but sometimes it reacts to harmless bacteria, pollen, food, or even the body’s own cells. The belief that something in the GI tract causes microscopic colitis is supported by evidence that the colon, when empty for a long time, recovers from inflammation. Scientists believe one’s genes may make a person more likely to develop microscopic colitis. Although a gene unique to microscopic colitis has yet to be found, dozens have been linked to other forms of IBD. Scientists have proposed several possible substances that might trigger microscopic colitis.
Harmful and harmless bacteria
Some people get microscopic colitis after being sick with certain harmful bacteria, including Yersinia enterocolitica, Campylobacter jejuni, and Clostridium difficile. Other people test negative for these and other harmful bacteria, but their condition improves with antibiotic treatment, suggesting normally harmless bacteria in the colon may trigger microscopic colitis in some people.
No medications have been proven to cause microscopic colitis but several have been linked to it, including:
- Acarbose (Prandin)
- Aspirin in very high dose
- Lansoprazole (Prevacid) and perhaps other PPI (proton pump) acid blockers (rare)
- Nonsteroidal anti-inflammatory drugs (NSAIDs), some brands more than others
- Ranitidine (Zantac), rarely, or other “histamine H2” blockers used for acid control (rare)
- Sertraline (Zoloft) anti depressant
Certain foods appear to trigger microscopic colitis in some people. Although no specific foods have been identified, following a caffeine- or lactose free diet sometimes improves symptoms.
Microscopic colitis can affect anyone but is more common in people ages 45 and older. Rates of microscopic colitis are similar to other forms of IBD, affecting about nine people in 100,000. Although microscopic colitis affects both men and women, microscopic colitis is much more common in women.
Signs and Symptoms
Chronic watery and non-bloody diarrhea is the main symptom of microscopic colitis. Episodes of diarrhea can last for weeks, months, or years. Most cases are interrupted by similarly long periods of remission—times when diarrhea goes away.
Scientists believe diarrhea associated with microscopic colitis is caused by the intestinal lining’s reduced ability to absorb electrolytes—salts and minerals in the body. The resulting electrolyte imbalance decreases the colon’s ability to absorb fluid and increases fluid secretion into the colon.
Other common symptoms of microscopic colitis include abdominal cramps or pain, usually less bothersome than the urgency of bowel movement or abdominal bloating.
Less common symptoms of microscopic colitis include:
- Mild weight loss, due to avoiding food in order to avoid getting diarrhea.
- Dehydration, due to avoiding drinking fluid in hopes diarrhea will lessen
- Fecal incontinence—inability to control a bowel movement
Screening and Diagnostic Tests
Microscopic colitis can only be diagnosed by examining intestinal tissue removed during colonoscopy or flexible sigmoidoscopy—procedures that use a lighted, flexible scope to see inside the colon and rectum. Before colonoscopy or flexible sigmoidoscopy, the doctor will rule out other conditions that cause diarrhea by asking questions about symptoms and performing tests on blood and stool to look for signs of infection or other causes of diarrhea.
During colonoscopy, the doctor can rule out even more conditions by looking at the lining of the colon. If the colon lining appears normal, the doctor may suspect microscopic colitis and will remove small biopsy samples of tissue using a tool passed through the scope. Because inflammation from microscopic colitis can occur in patches, the doctors will biopsy several areas of the colon. After tissue has been collected, a pathologist—a doctor trained to diagnose diseases based on tissue appearance—examines the tissue with a microscope.
Treatment for microscopic colitis often begins with eliminating medications with suspected links to microscopic colitis and cutting out foods that can make diarrhea worse, including foods containing caffeine, high-fat foods, and lactose-containing dairy products.
Antidiarrheal medications such as bismuth subsalicylate (Pepto-Bismol) and loperamide (Immodium) are effective for some patients, but used in higher than typical “bottle label” doses. For example, we’ll have patients with mild cases use loperamide 1-3 caplets before meals and bedtime, and take bismuth 2 tablespoons or tablets after meals and bedtime for up to a few weeks at a time and taper down doses when symptoms are better. The bismuth seems to help relieve the inflammation and symptoms may stay cleared up then without treatment for considerable periods.
If diarrhea persists, medications called corticosteroids may help, including prednisone (rarely) and budesonide (Entocort). Corticosteroids have many potential side effects including insomnia, fluid retention, and mood swings. Budesonide has fewer side effects than other corticosteroids because very little of it is absorbed, and it often works very quickly and completely to treat flare-ups of microscopic colitis. Other medications sometimes used to treat microscopic colitis include mesalamine and cholestyramine (Questran), the antidiarrheal medicine diphenoxylate (Lomotil). Any medication used is tapered off once good control of the condition occurs.
People with microscopic colitis generally achieve relief through treatment, although relapses can occur. Some patients require long-term therapy because they experience prompt relapse when treatment is stopped. Unlike other forms of IBD, microscopic colitis usually has no complications. It doesn’t appear to change into other forms of IBD and does not have any extra risk of colon cancer. Budesonide can have complications with high dose long-term use, so clinicians should always supervise treatment.
Lifesyle and Home RemediesChanges to your diet may help relieve diarrhea that you experience with microscopic colitis. Try to:
Drink plenty of fluids. Water is best, but fluids with added sodium and potassium (electrolytes) may help as well. Choose soft, easy-to-digest foods. These include applesauce, bananas and rice. Avoid high-fiber foods such as beans, nuts and raw vegetables. If you feel as though your symptoms are improving, slowly add high-fiber foods back to your diet.
Eat several small meals rather than a few large meals. Spacing meals throughout the day may ease diarrhea.
Avoid irritating foods. Stay away from spicy, fatty or fried foods and any other foods that make your symptoms worse.