How Do You Diagnose Ulcerative Colitis?

How Do You Diagnose Ulcerative Colitis?

Ulcerative colitis is a condition that causes blood stool, diarrhea, rectal pain and other symptoms. Ulcerative colitis is diagnosed with blood tests, stool tests and imaging tests.

Ulcerative colitis is a condition that causes blood stool, diarrhea, rectal pain and other symptoms. Ulcerative colitis is diagnosed with blood tests, stool tests and imaging tests.

It is OK to experience a bout of occasional abdominal cramps and diarrhea. However, if you have been experiencing these symptoms frequently, consult your doctor. It may be a sign of inflammatory bowel disease (IBD), such as ulcerative colitis.

Your doctor will diagnose ulcerative colitis after looking at several factors, including your medical history, a physical exam and a series of medical tests. They will ask if anyone in your family has ulcerative colitis. They will also ask you about other signs and symptoms of ulcerative colitis, including

In children, the condition can also affect their rate of growth.

The symptoms of ulcerative colitis are not the same in each affected person. Nearly half of the affected people experience mild symptoms of the disease. The condition increases your risk of colorectal cancer. Hence, visiting your doctor and getting diagnosed and treated early is important.

What laboratory tests help diagnose ulcerative colitis?

Your doctor would conduct a few blood tests and a stool test to identify if the cause of your symptoms is ulcerative colitis or something else.

Blood tests: A low red blood cell count (RBC) and low hemoglobin level indicate that you have anemia, which is a symptom of ulcerative colitis.

If you have ulcerative colitis, your blood test may show an increase in white blood cells, a low level of the protein albumin and an elevated C-reactive protein (CRP) level.

Stool test: Your stool test can let your doctor know if your symptoms are due to infections, such as gastroenteritis.

What imaging tests are used in the diagnosis of ulcerative colitis?

If your laboratory reports are suggestive of inflammatory bowel disease (IBD), they will refer you to a gastroenterologist. A gastroenterologist is a doctor who specializes in treating digestive system disorders. The gastroenterologist will recommend that you undergo tests, such as sigmoidoscopy and colonoscopy. Each of the procedures requires you to take laxatives a night before to empty your colon.


  • A sigmoidoscopy involves the insertion of a flexible tube-like camera into the anus to view the inside of the rectum and lower part of the colon.
  • This procedure helps the doctor know the extent of inflammation and ulcers, if any, in the lower colon.
  • The procedure usually takes about 15 to 20 minutes and you can go home the same day.
  • If you have been given medicines that make you sleepy, you need to stay for a few hours at the clinic or hospital until the doctor allows you to go home.


  • If your doctor suspects that the inflammation and ulcerations have spread beyond your lower colon, they may ask you to undergo another procedure called colonoscopy.
  • Similar to sigmoidoscopy, this procedure also uses a flexible tube with a lighted camera on it, which helps the doctor to view the inside of the entire colon and diagnose ulcerative colitis.
  • You do not need to stay overnight after the procedure. You will be allowed to go home the same day. Sometimes, you have to swallow a capsule that contains a camera and it can take pictures of your GI system. This is called capsule endoscopy. It is less painful compared to standard colonoscopy.
  • If the doctor suspects colon cancer, they will remove a small piece of the colon. This procedure is called biopsy. The biopsied sample is then sent to the laboratory for examination under a microscope.

X-rays or computed tomography (CT) scan

  • If your doctor wants to check if you have developed any complications of ulcerative colitis, they may order additional tests, such as a CT scan or X-ray of your abdomen. A CT scan uses strong radiation to get detailed images of the colon and other organs of your abdomen.

Magnetic resonance imaging (MRI)

  • Like a CT scan, an MRI also provides detailed pictures of the colon. The only difference is that it uses strong magnets and not radiation.

Endoscopic retrograde cholangiopancreatography (ERCP)

Medically Reviewed on 7/23/2021


Medscape: “Ulcerative Colitis.”

Mayo Clinic: “Ulcerative Colitis.”