Microscopic colitis is an inflammation of the colon, which interferes with absorption of water from the colon and, consequently, causes persistent watery diarrhea. The disorder gets its name from the fact that it is not visible with bare eye, but it is necessary to examine colon tissue under a microscope to identify it.

There are two types of microscopic colitis:

  • Collagenous colitis, in which a thick layer of protein (collagen) develops just below the colon tissue. The symptoms of microscopic colitis can come and go frequently, sometimes resolving on their own; and
  • Lymphocytic colitis, in which white blood cells (lymphocytes) increase in colon tissue, where they accumulate.

It is not known whether collagenous colitis and lymphocytic colitis are two separate disorders or represent different phases of the same condition. However, the symptoms of collagenous colitis and lymphocytic colitis are similar, as are testing and treatment, since some experts believe that they represent different stages of the same disease.



The primary symptom of microscopic colitis is chronic, watery diarrhea that can last for months or years before the diagnosis is made. Typically, the symptoms begin very gradually and are intermittent in nature with periods when the person feels well, followed by bouts of chronic diarrhea. This chronic diarrhea of microscopic colitis is different from the acute diarrhea of infectious colitis, which typically lasts only days to weeks. Some other symptoms of microscopic colitis include:

  • Abdominal pain or cramps;
  • Weight loss;
  • Nausea;
  • Fecal incontinence.



It is not clear what causes the inflammation of the colon found in microscopic colitis. Some experts suspect that microscopic colitis is an autoimmune disorder similar to the autoimmune disorders that cause chronic ulcerative colitis and Crohn's disease. Researchers believe that the causes may include:

  • Medications that can irritate the lining of the colon
  • Bacteria that produce toxins that irritate the lining of the colon
  • Viruses that trigger inflammation
  • Immune system problems, such as rheumatoid arthritis or celiac disease, that occur when the body's immune system attacks healthy tissues


Risk Factors

Even though not all research studies agree, some of them indicate that using certain medications may increase the risk of microscopic colitis. Medications linked to the condition include:

  • Aspirin, acetaminophen and ibuprofen;
  • Proton pump inhibitors, including lansoprazole;
  • Acarbose;
  • Flutamide;
  • Ranitidine;
  • Selective serotonin reuptake inhibitors, such as sertraline;
  • Carbamazepine.

Some categories of persons are considered to be at greater risk for developing microscopic colitis. Those are:

  • Women in the age group from 50 to 70;
  • People with certain immune system problems, such as celiac disease, thyroid disease or rheumatoid arthritis;
  • Smokers, especially in the ages from 16 to 44.



Since the cause of microscopic colitis is not known, no certain advice can be provided about preventing this disease.