Diagnosing ulcerative colitis may involve laboratory tests and one or more procedures that allow the doctor to visualize the intestine.
It is important that if inflammatory bowel disease is suspected, a correct diagnosis of either ulcerative colitis or Crohn's disease be made. While the two diseases have many similarities, they are distinct, and many of the newer drug treatments work better for one disease than the other.
The three diagnostic tests most frequently used are:
Certain laboratory tests also can be used to confirm a diagnosis of ulcerative colitis.
Sigmoidoscopy is a procedure that allows direct visualization of the lower gastrointestinal tract; that is, the rectum and the sigmoid colon. It is most often performed with a flexible fiber-optic scope that contains a light source and a camera lens. A short, rigid scope also may be used. The camera records images that are displayed on a monitor.
The sigmoidoscope is gently inserted into the anus, then moved up through the rectum into the colon. Sigmoidoscopy can be performed in a doctor's office or health clinic. The procedure takes five to 20 minutes, and no sedation is needed.
The doctor looks for irregularities in the mucosal lining (that is, the inner lining) of the colon. Changes to the bowel lining are continuous in ulcerative colitis, with no area of normal tissue between areas of diseased tissue.
For most people, sigmoidoscopy is mildly uncomfortable. However, for individuals who are in the midst of a
Bowel preparation includes using one or two pre-mixed enemas about two hours prior to the procedure in order to cleanse the rectum and sigmoid colon of stool.
Colonoscopy is a more thorough examination of the entire colon, right up to the end of the small intestine (the terminal ileum). Modern colonoscopes, using microchip-driven electronic imaging and screen projection, have replaced older fiber-optic scopes. As with the sigmoidoscope, the colonoscope is inserted gently into the anus, and moved up through the colon.
There is also a small set of forceps inside the colonoscope that the doctor can control in order to remove
Colonoscopy takes about 30 minutes. It is done under what is known as "conscious anesthesia," a combination of a sedative and pain medication that puts the individual into a semi-conscious state.
- Because of the use of this sedation, the procedure must be done in a hospital or in an endoscopy suite that has been approved and licensed by the state and provides the required emergency care for anesthesia-related complications.
- Because most people remain drowsy for some hours after the procedure, it is usually necessary to take the day off from work to undergo a colonoscopy.
The bowel preparation for a colonoscopy must be more thorough than for a sigmoidoscopy. It usually begins the afternoon prior to the exam and includes one or two laxative treatments and only drinking clear liquids for 12 to 18 hours before the exam, in order to completely purge the colon.
In this procedure, a special dye called barium is inserted into the colon through a tube inserted into the rectum, and a series of X-rays is taken. Often, air is also inserted to help fill out the colon to make it easier for the X-rays to pick out abnormalities.
Plain-film X-rays without barium do not distinguish soft tissues well, especially the lining of the bowel, which must be seen clearly if the proper diagnosis is to be made.
The barium enema is considered the "gold standard" in distinguishing between ulcerative colitis and Crohn's disease because:
- Enough barium usually goes beyond the colon into the terminal ileum to see if that area is diseased
- The barium allows the radiologist and the gastroenterologist to see if the disease is continuous or if it skips from patches of diseased tissue to healthy tissue and back again
As in colonoscopy, the bowel preparation for a barium enema must be thorough. It usually begins the afternoon prior to the exam and includes one or two laxative treatments and only drinking clear liquids for 12 to 18 hours before the exam, in order to completely purge the colon.
A number of laboratory tests can help confirm a diagnosis of ulcerative colitis.
As part of a rectal exam, a doctor tests to see if there is any blood in the stool (called occult blood). Occult blood signals bleeding in the intestinal tract.
Blood drawn from a vein in the arm may be tested as well. The white blood cell count may be elevated, as might the red blood cell sedimentation rate (ESR). The ESR is the rate at which blood separates into its component parts of red blood cells at the bottom and plasma at the top, with other components in the middle.
A higher-than-normal sedimentation time (elevated ESR), combined with an elevated white cell count, suggests an inflammatory process, but is not specific at all. The blood count may be low, suggesting anemia (which can be due to the malabsorption of iron), excessive internal bleeding, or chronic illness, all of which occur with ulcerative colitis or Crohn's disease.