Overview

Microscopic colitis is an inflammation of the large intestine (colon) that causes persistent watery diarrhea. The disorder gets its name from the fact that it's necessary to examine colon tissue under a microscope to identify it, since the tissue may appear normal with a colonoscopy or flexible sigmoidoscopy.

There are different subtypes of microscopic colitis:

  • Collagenous colitis, in which a thick layer of protein (collagen) develops in colon tissue
  • Lymphocytic colitis, in which white blood cells (lymphocytes) increase in colon tissue
  • Incomplete microscopic colitis, in which there are mixed features of collagenous and lymphocytic colitis.

Researchers believe collagenous (kuh-LAYJ-uh-nus) colitis and lymphocytic colitis may be different phases of the same condition. Symptoms, testing and treatment are the same for all subtypes.

Symptoms

Signs and symptoms of microscopic colitis include:

  • Chronic watery diarrhea
  • Abdominal pain, cramps or bloating
  • Weight loss
  • Nausea
  • Fecal incontinence
  • Dehydration

The symptoms of microscopic colitis can come and go frequently. Sometimes the symptoms resolve on their own.

When to see a doctor

If you have watery diarrhea that lasts more than a few days, contact your doctor so that your condition can be diagnosed and properly treated.

Causes

It's not clear what causes the inflammation of the colon found in microscopic colitis. 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.
  • Autoimmune disease associated with microscopic colitis, such as rheumatoid arthritis, celiac disease or psoriasis. Autoimmune disease occurs when your body's immune system attacks healthy tissues.
  • Bile acid not being properly absorbed and irritating the lining of the colon.

Risk factors

Risk factors for microscopic colitis include:

  • Age. Microscopic colitis is most common in people ages 50 to 70.
  • Sex. Women are more likely to have microscopic colitis than are men. Some studies suggest an association between post-menopausal hormone therapy and microscopic colitis.
  • Autoimmune disease. People with microscopic colitis sometimes also have an autoimmune disorder, such as celiac disease, thyroid disease, rheumatoid arthritis, type 1 diabetes or psoriasis.
  • Genetic link. Research suggests that there may be a connection between microscopic colitis and a family history of irritable bowel syndrome.
  • Smoking. Recent research studies have shown an association between tobacco smoking and microscopic colitis, especially in people ages 16 to 44.

Some research studies indicate that using certain medications may increase your risk of microscopic colitis. But not all studies agree.

Medications that may be linked to the condition include:

  • Pain relievers, such as aspirin, ibuprofen (Advil, Motrin IB, others) and naproxen sodium (Aleve)
  • Proton pump inhibitors including lansoprazole (Prevacid), esomeprazole (Nexium), pantoprazole (Protonix), rabeprazole (Aciphex), omeprazole (Prilosec) and dexlansoprazole (Dexilant)
  • Selective serotonin reuptake inhibitors (SSRIs) such as sertraline (Zoloft)
  • Acarbose (Precose)
  • Flutamide
  • Ranitidine
  • Carbamazepine (Carbatrol, Tegretol)
  • Clozapine (Clozaril, Fazaclo)
  • Entacapone (Comtan)
  • Paroxetine (Paxil, Pexeva)
  • Simvastatin (Zocor)
  • Topiramate

Complications

Most people are successfully treated for microscopic colitis. The condition does not increase your risk of colon cancer.