What is collagenous colitis?

Collagenous colitis (CC) is a condition that affects your large intestine. It leads to episodes of watery diarrhea and belly pain.

Your large intestine is part of your digestive (gastrointestinal or GI) tract. The GI tract goes from your mouth all the way to your rectal opening. The large intestine includes both the colon and the rectum. The large intestine receives the broken-down products of food from the small intestine. One of its main jobs is to reabsorb water and electrolytes, such as salt. The colon leads to the rectum. The rectum stores your bowel movements before your body eliminates them.

In CC, inflammatory cells from your immune system travel to your large intestine. Once there, they cause swelling and inflammation. In rare cases, these cells also go into the latter part of your small intestine.

This inflammation may keep your large intestine from reabsorbing as much water as it should. This can lead to diarrhea, belly pain, and other symptoms. The inflammation may also cause extra collagen to build up in the wall of your small intestine. Collagen is a stretchy, supportive substance.

CC is one type of inflammatory bowel disease (IBD). IBD is group of conditions that cause inflammation in either the small or large intestine. CC is a type of microscopic colitis. Microscopic colitis is inflammation of the large intestine that can be seen only through a microscope. The other main type of microscopic colitis is lymphocytic colitis. Some experts think lymphocytic colitis and CC might be the same illness presented in different ways.

CC is pretty uncommon. It’s more common in older adults. But it can affect younger adults and children. It’s also seen more in women than in men.

What causes collagenous colitis?

Experts are trying to understand what causes the inflammation of the large intestine that leads to CC. Some people think that something in the GI tract sets off this abnormal immune response. This might be bacteria, pollen, or food.

Taking certain medicines may also set off the condition in some people. These medicines can include:

• Nonsteroidal anti-inflammatory drugs. These include aspirin, naproxen, and ibuprofen.

• Acid reflux medicines

• High cholesterol medicines

• Diabetes medicines

• Medicines to treat depression

• High blood pressure medicines

Certain bacteria may set off CC in some people. You might have your first episode after getting sick from bacteria. These can include Campylobacter jejuni or Clostridium difficile. Toxins in these bacteria may harm the inner surface of your large intestine. This can cause inflammation. Some experts think certain viruses may also play a role in CC.

Foods are not clearly proved to be a cause of collagenous colitis, but certain foods may make CC symptoms worse. These can include caffeine and milk products.  

Who is at risk for collagenous colitis?

Having certain health issues may increase your risk for the disease. These include:

• Diabetes

• Celiac disease

• Thyroid disease

• Irritable bowel syndrome

Being a smoker may increase your risk for the condition. Smoking interferes with the blood flow that your intestines need. Your risk for CC may also be higher if someone in your family has the condition or another inflammatory bowel disease.

What are the symptoms of collagenous colitis?

The main symptom of CC is watery diarrhea. This diarrhea does not have blood. You may have several of these watery bowel movements each day. This may last for weeks or months. For most people, this diarrhea goes away for a while, but then it comes back later.

Other symptoms of CC may include:

• Weight loss

• Belly pain

• Bloating

• Dehydration

• Nausea

• Fatigue or weakness

• Joint pain

• Not being able to control a bowel movement

How is collagenous colitis diagnosed?

You may need to see a gastroenterologist. This healthcare provider has special training to treat problems with the digestive system.  

Your healthcare provider will ask you about your health history and your symptoms. Your provider will give you an exam, including an exam of your abdomen.

Your healthcare provider will rule out other causes of your diarrhea. These can include an infection or another inflammatory bowel disease.

Your healthcare provider will also do other tests. These may include:

• Blood tests, such as those to check for anemia

• Blood tests to check for infection

• Tests for celiac disease

• Stool analysis to check for inflammation or infection

You may also need a colonoscopy. This test looks at the lining of your colon and rectum. It uses a light and a tiny camera.

The colon often looks normal on a colonoscopy. During the colonoscopy, your healthcare provider can take out a small sample of tissue from your colon. This is called a biopsy. The tissue is looked at under a microscope to see if you have CC.

How is collagenous colitis treated?

Your healthcare provider may prescribe medicines and suggest diet changes to treat your CC.

What are possible complications of collagenous colitis?

Unlike other forms of inflammatory bowel disease, CC doesn’t seem to increase your risk for colon cancer. It does not increase your risk of death from any cause.

When should I call my healthcare provider?

Call your healthcare provider if your symptoms don’t go away with treatment. Your healthcare provider may change your treatment plan.

Key points about collagenous colitis

• CC is a condition that affects your large intestine. It leads to episodes of watery diarrhea and belly pain.

• Bacterial and viral infections and certain medicines may set off CC in some people. But often the cause isn't known.

• You may have a colonoscopy to diagnose this condition. During this test, your healthcare provider may take out a sample of your large intestine and look at it through a microscope.

• You may need to take medicines to treat your condition. You may also need to stay away from certain foods and medicines that set off your symptoms.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your healthcare provider if you have questions, especially after office hours or on weekends and holidays.