Microscopic Colitis


Less Common Forms of Colitis

Colitis is literally defined as inflammation of the colon. But it's actually a catch-all term that covers a wide range of symptoms, from intermittent, watery diarrhea to acute pain and inflammation. Excluding infectious colitis, ulcerative colitis and Crohn’s disease involving the colon are both the best known and the most severe form of the disease, but there are two major additional types of colitis -- microscopic colitis and ischemic colitis -- each with its own symptoms and treatment requirements.

Microscopic Colitis

Microscopic colitis, which includes collagenous colitis and lymphocytic colitis, is characterized by chronic diarrhea caused by inflammation in the colon. It is not related to ulcerative colitis or to Crohn's disease, which are more severe forms of inflammatory bowel disease. There is also no evidence to suggest that microscopic colitis carries the same increased risk for colon cancer as ulcerative colitis.

This condition is known as "microscopic" colitis because physicians can't see the inflammation without a microscope. When looked at through an endoscope -- a camera mounted at the end of a long, flexible tube that's inserted in the rectum -- either during a colonoscopy or sigmoidoscopy, the colon appears entirely normal.

"That's why everyone who has chronic diarrhea and is having a colonoscopy should also have a biopsy done," insists John F. Valentine, M.D., Professor in the Division of Gastroenterology, Hepatology, and Nutrition at the University of Utah. "Even if the lining of the colon looks normal, it's essential to remove tissue samples for microscopic analysis." Without these diagnostic steps, it could take weeks, months, or even years to discover the reason for the chronic diarrhea.

Once the biopsy samples are examined under a microscope, various features may reveal the source of the inflammation and pinpoint the diagnosis even further. "For example," says Dr. Valentine, "if the biopsy shows inflammation and a thickened, non-elastic band of tissue made of a protein, called collagen, just beneath the lining of the colon, then the condition is known as collagenous colitis. Because the thickness of the band may vary, it may be necessary to look at several different tissue samples from different areas of the colon before arriving at the diagnosis." It is important to note that collagen is normally present just beneath the lining of the colon. In collagenous colitis, however, the amount of collagen is increased.

Another type of microscopic colitis is lymphocytic colitis. In this case, biopsy samples reveal an increased number of lymphocytes, specialized white blood cells that fight infection and disease, within the lining of the colon. Lymphocytes may be seen in collagenous colitis, too, which somewhat blurs the distinction between the two conditions. A thickened collagen band isn't seen in lymphocytic colitis, though.

What Causes Microscopic Colitis, and Who Gets It?

What's responsible for the damaged lining of the colon in microscopic colitis? As with ulcerative colitis and Crohn's disease, the exact cause has yet to be identified. But bacteria, bacterial toxins, and viruses are among the usual suspects that have been implicated.

Some experts have suggested that nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin or ibuprofen, might be the actual culprits. It is also possible that these medications might simply aggravate symptoms in individuals who are already prone to the syndrome. Another theory is that collagenous colitis and lymphocytic colitis are caused by an autoimmune response, which means that the body launches an attack upon itself -- mistaking various cells in the colon for foreign intruders. The final answer may well turn out to be some combination of these theories.

There does seem to be a particular link between microscopic colitis and the autoimmune disease celiac sprue, also known as celiac disease. Caused by an immunologic reaction of the intestine to wheat, barley, rye, and oats, celiac sprue is a digestive disease that damages the small intestine and interferes with absorption of nutrients. Its hallmarks are chronic diarrhea and weight loss.

"Celiac sprue is underdiagnosed in this country," says Dr. Valentine. "That's because not everyone who has this disease has all the classic symptoms. Some people with celiac sprue have microscopic tissue changes that can look a lot like microscopic colitis, so there does seem to be some clinical overlap between the two conditions."  It is important to exclude celiac disease as a cause or contributor to the diarrhea in patients with microscopic colitis.

When it comes to collagenous colitis, the average age at onset is in the 50s -- and is predominantly in women. "In fact," notes Dr. Valentine, "some studies have shown that women with celiac disease outnumber men by five to one or more. That's not totally surprising, since autoimmune diseases tend to be more common in women. In the case of lymphocytic colitis, however, the condition is more evenly distributed between men and women. Age at onset tends to be a bit later, with diagnosis usually in the 60s."

Symptoms and Treatment

Although collagenous colitis and lymphocytic colitis display different characteristics under magnification, the symptoms of the two forms of microscopic colitis are virtually identical. "The chief complaint with both conditions is chronic watery diarrhea with no sign of blood in the stool," observes Dr. Valentine. "The diarrhea may be either continuous or intermittent and may be accompanied by cramps or abdominal pain. Dehydration may occur as well."

Treatment for collagenous colitis and lymphocytic colitis varies. "Sometimes these conditions resolve on their own, but usually once they're diagnosed, a treatment is initiated," explains Dr. Valentine. "Because the symptoms tend to wax and wane, the therapeutic approach depends a lot on  the severity of the diarrhea. Is the person having three or four loose stools a day or 15?

As the first line of therapy, treatment generally starts with bulk-forming agents such as psyllium (Metamucil®), or various antidiarrheals that act as antimotility agents to slow the contractions that move bowel contents forward. These include loperamide (Imodium®) and diphenoxylate (Lomotil®). There are data indicating that bismuth subsalicylate (Pepto Bismol®) can be of benefit, too. While none of these actually addresses the cause, they do provide symptomatic relief.

The next line of therapy might be antibiotics or anti-inflammatory medications, such as mesalamine (Pentasa,® Asacol,® Colazal,® Dipentum®, Lialda®, Apriso®) and sulfasalazine (Azulfidine®), or budesonide (Entocort®). Oral corticosteroids like prednisone are useful for reducing inflammation, but they also carry some significant side effects -- like high blood pressure, osteoporosis, and diabetes -- that may outweigh their benefits. "Once the symptoms improve with steroids, we try to discontinue them and leave the patient on mesalamine products for a while," says Dr. Valentine. "Eventually, we stop those as well and treat on an as-needed basis."

Ischemic Colitis

Collagenous and lymphocytic colitis usually come on gradually. They're known as chronic diseases – those that start gradually and tend to be long-term. The same cannot be said for ischemic colitis. Ischemia is a condition in which the oxygen-rich blood flow to a part of the body is restricted; ischemic colitis is marked by a blockage of blood supply to the colon. Even though it can take time for the blood supply to the colon to become blocked, once it does, the condition of ischemic colitis itself usually requires immediate attention.

"It's just like other ischemic problems," says Dr. Valentine. "The older you get, the more you have to think about this diagnosis. Ischemic colitis is found almost exclusively in the elderly and in those with vascular problems. It's caused by problems in the blood vessels that, in turn, prevent the bowel from getting enough blood. As with coronary artery disease, the blockage can be chronic -- caused by fatty deposits in the arteries that lead to the colon -- or it can be acute (sudden), caused by blood clots. The typical presentation is sudden onset abdominal pain and bloody diarrhea, but the severity  may vary depending on the severity of the ischemia.

"Ischemic colitis should be suspected in any older individual who has bloody diarrhea," he adds. "In addition to abdominal pain, low-grade fever also may be present. All of these symptoms, in addition to the person's age, should point to a diagnosis of ischemic colitis. It's a pretty dramatic presentation, so the diagnosis is usually made quickly, unlike with collagenous or lymphocytic colitis. Still, you do need to do stool testing and a colonoscopy to exclude other forms of inflammation like infection, diverticulitis, or IBD."

A diagnosis of ischemic colitis calls for hospitalization. Intravenous fluids are given to allow the colon to rest, and antibiotics are often administered to prevent infection. "Most people get better within a few days," says Dr. Valentine. "Then they can start eating again and the antibiotics are discontinued. If the ischemia is especially severe, prolonged, or has recurred at the same spot repeatedly, then surgical resection -- removal of the affected area of the colon -- may be necessary."

It's not easy to live with colitis of any kind, whether ulcerative, microscopic, or ischemic. It's important to talk to your doctor if you are experiencing any symptoms that could possibly indicate microscopic or ischemic colitis. Working with your doctor is the only way to get an accurate diagnosis and receive the right treatment for your particular condition.



For further information, call the Irwin M. and Suzanne R. Rosenthal IBD Resource Center (IBD Help Center): 888.MY.GUT.PAIN (888.694.8872).

The Crohn’s & Colitis Foundation of America provides information for educational purposes only. We encourage you to review this educational material with your health care professional. The Foundation does not provide medical or other health care opinions or services. The inclusion of another organization’s resources or referral to another organization does not represent an endorsement of a particular individual, group, company or product.

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Published: October 22, 2012