How Doctors Diagnose Ulcerative Colitis

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Ulcerative colitis is an autoimmune disease that causes inflammation and sores in the inner lining of the large intestine. Ulcerative colitis can be difficult to diagnose because its symptoms are similar to other intestinal problems, including Crohn’s disease. 

The first step in reaching a diagnosis is to see a gastroenterologist, a doctor who specializes in intestinal problems. Some people refer to gastroenterologists as GI (gastrointestinal) doctors. Your doctor will physically examine you and ask questions about your symptoms and medical history. Partner with your doctor to identify the problem. With a correct diagnosis, you can begin treatment and feel better.  

Understanding Your Symptoms

It’s important to provide as much information as you can about your symptoms and when they occur. This helps your doctor understand you and your condition. If possible, keep a journal of your symptoms and bring it with you to your appointment. Log your bowel movements, any bleeding, diarrhea, fevers, joint aches, and other symptoms. Write down when they start, how long they occur, and what makes them better or worse.

For example, you may log that you began an episode of diarrhea at 6:30 p.m., 30 minutes after eating a large meal, and you noticed blood in the diarrhea. This kind of detail can help your doctor investigate your condition. 

Conducting Routine Testing

Your doctor will also suggest blood and stool tests as part of the initial exam. 

A blood test can help identify a high white blood cell count, a signal there is inflammation in the body. Blood tests can also detect if you are anemic, which can occur due to bleeding in the colon or rectum. 

A stool test involves collecting a sample of stool and sending it for analysis. In addition to identifying high white blood cell counts, it can also help doctors rule out other causes of diarrhea, such as a bacterial or viral infection

Although blood and stool tests are helpful, they can’t tell your doctor what is causing your intestinal problems. However, they serve as confirmation that more tests are needed to find the cause of the inflammation. 

Benefits of Colonoscopy

The standard test doctors use to accurately diagnose ulcerative colitis is a colonoscopy. A colonoscopy can also rule out Crohn’s disease, a very similar condition in which inflammation can occur anywhere in the gastrointestinal tract, not just in the lining of the large intestine. 

With a colonoscopy, your doctor can look inside the rectum and entire colon using an endoscope. Your doctor may also take a small tissue sample (biopsy) during the procedure. A doctor analyzes the tissue to make the diagnosis.  Sometimes your doctor may recommend a flexible sigmoidoscopy to diagnose ulcerative colitis. The test is similar to a colonoscopy but allows the doctor to view the rectum and only the lower colon. 

Why an Accurate Diagnosis Is Important

If you have ulcerative colitis, your symptoms may be very similar to or even the same as someone who has Crohn’s disease. Both are considered forms of inflammatory bowel disease. However, it’s important to know the exact cause and location of your inflammation. While some medications are used to treat both ulcerative colitis and Crohn’s disease, some are targeted only for treatment of ulcerative colitis.  

To help your doctor make an accurate diagnosis, be patient and remain an active participant in your testing and care. Together, you can pinpoint the reason for your symptoms and get the therapy you need.  

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Aug 2
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Colitis diagnosis and testing. Crohn’s and Colitis Foundation of America.
  2. Diagnosing and managing IBD. Crohn’s and Colitis Foundation of America. Ulcerative colitis. National Digestive Diseases Information Clearinghouse (NDDIC).