Colorectal cancer or colon cancer is the second most common cause of cancer death. The colon is the final part of the intestines and is also called the large intestine. Over ninety percent of all colon cancers occur in people over the age of 50. It is for this reason that men and women (without other risk factors) are encouraged to have routine screening colonoscopy procedures beginning at age 50. Since colon cancer is generally one of the slowest growing types of cancer, colonoscopy cancer screening is usually only performed once every ten years. In patients with certain risk factors or history of colon disease, colonoscopy screening may be indicated before the age of 50, or as frequently as every three to five years.
During a routine screening colonoscopy, a colonoscope, which is a thin, flexible tube with a light, camera, and some surgical instruments built into the tip, is guided into the anus and along the length of the colon. A colonoscopy is usually performed by a gastroenterologist (GI specialist). This physician inspects the walls on the inside of the colon for any abnormalities. One of the most common abnormalities encountered by the gastroenterologist during a routine screening colonoscopy is a polyp. Polyps are affixed to the internal wall of the colon and are surgically removed during the colonoscopy. Once the polyp is removed it is sent to a pathologist who determines whether or not the polyp contains cancer. Of note, the majority of polyps in the colon are not malignant cancer but are removed for testing anyway.
A successful colonoscopy cancer screening requires proper bowel preparation. Unfortunately this usually means that the evening before a colonoscopy screening the patient must drink a large quantity (half a gallon!) of a salty solution. This solution causes the contents of the intestines to dissolve and liquefy so that they can be passed from the body. While this makes for an uncomfortable night, having an empty colon is absolutely critical for a colonoscopy cancer screening. If there is any feces remaining in the bowel, there is very little that the gastroenterologist can do at the time of the colonoscopy to remove it. This means that some of the wall of the colon cannot be seen and cannot be thoroughly checked for abnormalities.
Most people that have colonoscopy screening are awake during the procedure. In other words, most patients do not require general anesthesia. Since even a routine screening colonoscopy can be uncomfortable and anxiety-provoking, the procedure is often carried out under “twilight” anesthesia. Twilight anesthesia is a form of rather deep sedation in which drugs are given by mouth or into a vein to cause a state of profound relaxation. While people are intended to be conscious during twilight anesthesia, many fall asleep during the colonoscopy screening. In addition, the sedatives used to induce twilight anesthesia have amnesic effects—patients usually do not remember much about the procedure, even if they stayed awake during it.
Most routine screening colonoscopy procedures are done on an outpatient basis. This means that the patient does not need to stay in the hospital overnight and can leave the same day as the colonoscopy. Because of the twilight anesthesia or other sedatives used, patients are encouraged to have a friend or relative provide transportation after the colonoscopy screening.