What is Microscopic Colitis?

This is a form of colitis that causes chronic, watery diarrhea. The colon/large intestine looks normal when viewed with imaging or a colonoscopy, but biopsies (tissues samples that are examined under a microscope) show inflammation on a cellular level. There are two different types of microscopic colitis that have been established, lymphocytic and collagenous. If you have one of these disorders, there is no evidence that your life span will be shortened or have severe problems.

Who gets it?

Microscopic colitis typically occurs in middle aged or elderly patients, but it can affect anyone. Women are more commonly affected. Some studies say that microscopic colitis is more common in people with celiac disease, irritable bowel syndrome, and thyroid disease.

Why does it happen?

Normally, in the colon there is a collagenous band in the tissue that is 1-7 micrometers in thickness; in collagenous colitis it ranges form 7-100 micrometers. Collagen is a fiber the body produces that is present in connective tissue. In lymphocytic colitis, there is no thickening of this collagen band, but rather extra inflammatory cells (lymphocytes) present in the colon tissue.

Mainly, the colon is affected but the last part of the small intestine, the terminal ileum, can also have changes. Sometimes, there is overlap in these disorders; they may, or may not, be related but bring about similar symptoms. Why these abnormalities develop is unknown; there are several theories. With collagenous colitis perhaps the breakdown or the production of collagen is inappropriate or a toxin from bacteria causes injury to the colon lining. Medications may have a role in the development; specifically associated medications are listed in the table below. The diarrhea in this disorder is not related to the thickness of the collagen but mimics the severity of the inflammatory changes in the colon tissue so the loose stools are likely related to inflammation.

What are the symptoms?

Nonbloody chronic watery diarrhea, up to 2 liters

• Typically there are 4-9 stools daily
• In collagenous colitis typically the pattern is intermittent (85%) with periods that are symptom free, but can be continuous (13%) or even just a single episode (2%).
• Symptoms may resolve faster in lymphocytic colitis
• Nausea
• Abdominal pain
• Weight loss
• Fatigue

How is it Diagnosed?

Based on your symptoms, a colonoscopy may be performed, and just like the name implies, the diagnosis of MICROSCOPIC colitis is made with a microscope with a biopsy of the colon.

How is it Treated?

If microscopic colitis is thought to be drug induced, clearly that medicine will be stopped. Often the diarrhea will resolve within weeks with, or without, treatment but return of symptoms is common, happening in 30-60% of people.

If with stopping any triggering medicines, treating celiac disease or irritable bowel syndrome you continue to have symptoms, an antidiarrheal medicine like loperamide may be effective. If no benefit is seen, the following steps can be taken:

Budesonide (Entocort)
This is a steroid, similar to prednisone, which decreases inflammation and the activity of the immune system. It acts more locally within the colon without the widespread side effects of prednisone because of how it is broken down in the liver. One study showed that 60% of patients improved within 2 weeks, and 85% in 4-6 weeks in patients with collagenous colitis.

Aminosalicylates may be tried.

• Sulfasalazine (Azulfidine)
  Sulfasalzine is thought to act locally right at the lining of the GI tract in the colon to decrease inflammation.
  
• Olsalazine (Dipentum); balsalazide (Colazal)
  Olsalazine and balsalazide are converted to mesalamine, the active component of sulfasalazine, in the colon.
  
• Mesalamine (Oral: Apriso, Asacol, Asacol HD, Lialda, Pentasa; Rectal suppository or enema: Canasa, Rowasa)

The specific mechanism of mesalamine is unknown, but is it thought that it decreases the local inflammatory response right at tissue that is irritated.

• Bile acid binding.
  Cholestyramine and other agents possibly work by binding toxins from bacteria that may injure the colon lining in addition to bile acids which may not be absorbed properly.
  
• Prednisone.
  Prednisone decreases inflammation and the activity of the immune system, but is associated with many side effects and when treatment is stopped many people relapse.
  
• Bismuth subsalicylate.
  Bismuth works by stopping secretion into the colon, has antimicrobial action, and may help decrease inflammation.

There may be an association with gluten sensitivity and microscopic colitis, so even if you have not been diagnosed with celiac disease, but you are not responding to any of the above medications, a trial of a gluten free diet may be attempted.

Drugs Associated

If you're experiencing any of the above symptoms of microscopic colitis, call our gastroenterology offices at (715) 847-2558.

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