No single blood test alone can determine if you have inflammatory bowel disease. Doctors use information from blood and stool tests in combination with information from a person's medical history, endoscopy, and x-rays to come to a diagnosis of inflammatory bowel disease. Patients with inflammatory bowel disease may have anemia (low blood counts) or other signs of inflammation that can be determined by blood or stool tests. There are tests for antibodies in blood that may also suggest a person has inflammatory bowel disease, but they are not used alone to diagnose Crohn's disease or ulcerative colitis. There is a commercially available genetic tests for Crohn's disease, but it is used as a predictor of how the disease may behave and is not reliable to diagnose Crohn's disease.
Colonoscopy is a type of "endoscopy," or flexible camera, that provides very important information to make a diagnosis of Crohn's disease or ulcerative colitis. A gastroenterologist can look directly at the lining of the colon and small intestine and look for signs of inflammation like ulcers and narrowing (strictures). The doctor can also take biopsies, which are small samples of tissue, to look at under the microscope. Biopsies are often the best way to determine if a person has inflammatory bowel disease.
Colonoscopy is usually performed with sedation, so most patients will be asleep or sedated during the procedure. For many patients, the most difficult part of the procedure is taking the colonoscopy prep the day prior to the procedure. Because the prep is a very important step of the procedure, notify your doctor if you are unable to drink the prep as prescribed.
See picture below.
Video Capsule Endoscopy
Some patients with Crohn's disease may have inflammation in areas that cannot be seen by standard colonoscopy. The doctor may recommend a video capsule endoscopy. This is performed by swallowing a camera the size of a pill. The capsule takes video of the entire small intestines and sends the images to a recorder that is worn during the test. Biopsies cannot be performed with a video capsule endoscopy. There is small chance the capsule may get stuck in the intestines. If your doctor is recommending a video capsule endoscopy, be sure to inform your doctor if you have had surgery for Crohn's disease in the past as you may be at a slight increased risk of the capsule getting stuck.
See picture above.
There are several radiology tests that are used to help diagnose inflammatory bowel disease. Changes of ulcerative colitis or Crohn's disease may be seen on a CT scan, but the diagnosis cannot be made by CT scan alone. Special x-ray tests called a small bowel follow through or CT enterography may be used to determine if your small intestines have inflammation in areas that cannot be seen by colonoscopy. CT enterography is a special type of CT scan that identify inflammation in the small intestines compared to a regular CT scan. MR enterography is a type of MRI that can also see the small intestine but does not have any radiation.
The picture below shows a CT enterography with inflammation in the small intestine.