9 Tests Doctors Run During a Severe UC Flare and What They're Checking For

When a severe ulcerative colitis (UC) flare takes you to the hospital, your care team will run quite a few tests. They’ll want to see whether it’s truly your UC or some other infection causing your symptoms. If it is the UC, they’ll need to know whether the disease has progressed or whether your medications aren’t working. A series of blood, stool, and imaging tests will provide all this information. Your provider may order some of the following tests. 

People with UC are at higher risk of getting infected with the bacteriaClostridioides difficile (C. difficile or C. diff) than people who don’t have UC. The symptoms, which include diarrhea and abdominal pain, can look a lot like a UC flare. They can also make existing UC worse. A health care provider will take a stool (poop) sample and send it to a lab to test for this bacteria.

Fecal calprotectin, a protein found in stool, is a sign of intestinal inflammation. Your doctor may order testing for this protein at various times throughout the course of your UC. The test can show how well your medications are working when you are in remission and the extent of inflammation during a flare. 

C-reactive protein (CRP) is a protein that the liver makes and releases into the bloodstream. Whenever there’s inflammation in your body — from infection, injury, or autoimmune disease like UC — you’ll have more CRP in your blood. When you’re having a severe UC flare, your doctor will order a blood test to check levels of CRP. This will give them a sense of the extent of the inflammation and the severity of your UC. 

Albumin is another protein made by your liver that can tell doctors about your condition. They may look at albumin levels in your blood to check for inflammation, malnourishment, and — in case a medication change is needed — which medications may be more and less likely to work.

Erythrocytes are red blood cells. The sedimentation rate (ESR) is the time it takes for them to settle to the bottom of a test tube. If they sink to the bottom quickly (high ESR), it can signal to doctors that your UC is active and severe. ESR can help predict the likelihood that you’ll need some of your colon removed. It may also indicate to doctors whether steroids might help you. To measure ESR, a blood sample is drawn and sent to a lab for testing.   

In this minimally invasive test, a doctor inserts a thin, flexible tube with a camera and light on the end (endoscope) into the rectum to examine the lower part of your colon (the sigmoid colon). With this test, the doctor can see the extent of the inflammation in your colon and take tissue samples (biopsies). The biopsies are tested for cytomegalovirus (CMV) colitis — inflammation caused by a virus, which can lead to life-threatening toxic megacolon.

Your doctor might order a colonoscopy, which uses an endoscope inserted into the rectum to examine the entire colon and take biopsies. A colonoscopy can give a complete picture of all the inflammation and possible damage to your colon. But doctors only order this if other tests aren't enough to provide the information they need. That’s because in people with severe UC, there’s a risk that a colonoscope could tear the colon. 

Doctors only order this test for people with confirmed UC when they suspect there may be damage or inflammation higher up in the intestine, too. If this test is needed, the endoscope goes in through your mouth to examine your upper intestine. 

In severe UC, ultrasound can measure the thickness of your intestinal walls, a sign of inflammation and disease severity. It can also show how well medications are working. In this test, a doctor or ultrasound technician will move a wand-like device over your abdomen. An image of the inside will be transmitted to a monitor screen. It’s quick and painless.