1. I have ulcerative colitis, how often do I need to have a colonoscopy?
There are essentially two reasons to do a colonoscopy in patients with known ulcerative colitis. The first is to assess disease activity. If there has been a change in your symptoms, that is you are no longer responding to increased dosages of medications, or perhaps you have changed medication, your doctor may want to do a colonoscopy to see if your disease has progressed. Maybe you only had mild case involving the lower part of the colon, and now your entire colon is involved. Perhaps what you and your doctor think is a flare of your ulcerative colitis is actually an infection that needs to be treated differently. These are questions that can be answered with a colonoscopy.
The second, usually more important reason to do a colonoscopy in a patient with ulcerative colitis is to screen for colon cancer. Colon cancer is typically a slow growing disease. It is recommended that colonoscopy be performed as a screening test in patients without colitis beginning at age 50. The frequency can vary after that depending on the quality of prep, family history of colon cancer and number and size of polyps found. Because it takes a small colon polyp years to grow larger and turn into a cancer, it is typically safe to wait 3-5 years to do another colonoscopy even if you have a history of polyps.
In patients with ulcerative colitis however, you can have a colon without polyps one year, and then develop cancer the following year. The risk of colon cancer in ulcerative colitis increases with the duration of disease activity. Typically, patients with ulcerative colitis undergo colonoscopy every three years if their disease is controlled and they are asymptomatic. You should check with your doctor, however, as every case is different. It is however recommended that patients with longstanding disease undergo colonoscopy more frequently. If your disease only involves the bottom part of the colon (left colon) it is typically recommended after 25 years to undergo a yearly colonoscopy. If your disease involves the whole colon (pancolitis) it would be recommended that you undergo yearly colonoscopy after ten years. At the time of the colonoscopy, your doctor will take multiple biopsies throughout the entire colon, because it might very well be that the warning signs can only be detected under a microscope.
2. My friend has ulcerative colitis and undergoes frequent colonoscopies looking for colon cancer. I have Crohn's disease. Do I need to worry about cancer as well?
As the saying goes, location is everything. Your risk for cancer depends on the location of your Crohn's disease. Inflammation in the small intestine does not increase the risk of cancer. There is not a significantly increased incidence of small bowel cancer in patients with small bowel Crohn's disease. Crohn's disease however, involves the small intestine one third of the time, the colon one third of the time and both the small bowel and colon on third of the time. If you have Crohn's disease of the colon, the risk of colon cancer is the same as if you have ulcerative colitis. Again, depending on the duration and extent of your disease, your doctor will be recommending more frequent colonoscopy to rule out pre-cancerous colon lesions.