CT scans can be useful in ruling out complications and other conditions beyond ulcerative colitis. They can also provide helpful information about how extensive any inflammation in the digestive tract is.

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Symptoms alone aren’t enough to diagnose ulcerative colitis (UC), a condition that 600,000 to 900,000 people live with in the United States. That’s why doctors rely on medical imagery and other tests, including CT scans.

These CT scans offer important information about the extent and location of inflammation in the digestive tract. They can also be used to rule out many other complications that could cause the same symptoms as UC.

Here’s what you should know about getting a CT scan for UC and what you may want to discuss with your healthcare team to determine whether the results are accurate enough to diagnose along with your symptoms.

UC is a form of inflammatory bowel disease (IBD) that can resemble many other conditions and is difficult to properly diagnose.

In order to get an official UC diagnosis, your doctor will need to perform an endoscopic procedure where a tissue biopsy is also taken for testing. It is not possible to officially diagnose UC with just a scan.

However, inflammation and other signs of it may be visible.

CT scans are more limited than the images from an endoscopic procedure, but the images from a CT scan can still offer indications that a person has UC. For example, on a CT scan, your doctor may notice thickening bowel walls or an “accordion” sign.

Researchers have found that a healthy colon typically has a wall thickness less than 3 millimeters (mm), but for individuals with UC, they found that the average thickness recorded was 7.8 mm.

Perhaps even more telling that an individual has UC, the accordion sign appears on CT imagery as a result of oral contrast given during a CT scan getting trapped between thickened edematous haustral folds and mucosal ridges.

As mentioned, a CT scan can’t definitively prove that an individual has UC, but it’s a tool doctors can use to determine whether a colonoscopy is necessary to diagnoses, rule out the condition, or learn more about your UC.

CT scans can show where inflammation is located and help rule out serious complications. When CT imagery is taken with a contrast material to get a better picture of the small intestine/bowel wall thickness, it allows evaluation of extra-intestinal involvement and complications such as ulcers, fistulas, abdominal abscesses, or cellulitis.

If your doctor requests a CT scan for suspected UC, it will typically be done with contrast so that your doctor can see specific features like the “accordion” sign and thickening bowel walls that may be an indicator that one has UC.

IBD evaluation with a CT scan usually requires both oral and rectal contrast agents. These contrast agents are used to maximize colonic distension and opacification. This is important for identifying inflammation. It also allows for the identification of air and fluid cavities, so doctors can see complications like abscesses.

Colonoscopy and sigmoidoscopy are considered the gold standards for UC diagnosis, because these procedures allow doctors to look directly inside the colon with a camera. They also allow doctors to take a biopsy of an individual’s inflamed tissue to send to a lab for confirmation that what they have seen is UC.

Your doctor could request an MRI or X-rays instead of a CT scan depending on what areas of the colon they wish to see or what potential complications they are concerned about. For example, a standard X-ray may be used to rule out serious complications like a toxic megacolon or perforated colon.

Your doctor may also order a blood test to determine whether there are signs of anemia and inflammation. Stools samples may be taken to rule out other conditions and infections, too.

When to seek medical care

You should see your doctor anytime your UC symptoms worsen or change.

Severe UC flare-ups should be treated at the hospital with doctor oversight to prevent dehydration and to minimize the chances of potentially fatal complications.

Some signs of severe UC include:

  • more than 6 bowel movements in a day
  • bloody or mucus in diarrhea for 3 or more days
  • severe abdominal pain
  • fever or chills
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If you believe that you’re showing signs of UC or your UC symptoms are becoming more severe, it’s important to notify your doctor. They may wish to get a better idea of what is happening inside your digestive system with medical imagery like a CT scan.

CT scans don’t include a tissue biopsy or offer as detailed a view of the bowels as endoscopic procedures. However, they can be useful in ruling out other intestinal conditions and identifying signs of possible UC. They can also provide helpful information about how extensive any inflammation in the digestive tract is.