During a routine physical examination, Frank Renner, age 74, learns he has mild anemia. His doctor orders a colonoscopy to identify a source for the possible GI bleeding. But when Mr. Overview Colorectal cancer is second only to lung cancer as a cause of cancer deaths in the United States. Most colorectal cancers begin as polyps, which grow slowly over many years. The American Cancer Society recommends examination of the entire colon for all adults starting at age 50, and every 5 years after that.
Other organizations may recommend longer testing intervals. Colonoscopy is the best procedure for viewing the entire colon. However, because of the declining number of physicians who perform endoscopic procedures and the increasing numbers of Americans reaching age 50, some areas have long waiting lists for conventional colonoscopy.
Fortunately, many patients can undergo a noninvasive alternative called virtual colonoscopy, or computed tomography CT colonography. Far less physician-intensive, this noninvasive procedure can be done when conventional colonoscopy is contraindicated or when the waiting lists are long. Data obtained from the CT scans are used to create three-dimensional images of the colon similar to those obtained with conventional colonoscopy. Test preparation and procedure Before the test, the patient must prepare the bowelβtypically with a hour clear liquid diet and an over-the-counter bowel cleansing agent, such as Fleet Phospho-soda.
New bowel-cleansing regimens are being investigated to minimize bowel preparation and thus improve patient compliance. The procedure requires no I. Air or carbon dioxide is inserted through the rubber tube to inflate the colon for better visualization; the air distends the bowel and acts as a contrast medium.
During air insertion, some patients may experience slight, transient abdominal cramping. After several minutes, the patient is placed in a CT scanner and CT scans are takenβfirst with the patient in a supine position and then in a prone position. The entire test takes 10 to 20 minutes. Virtual colonoscopy is an accurate screening method for asymptomatic, average-risk adults and compares well with conventional colonoscopy in detecting clinically relevant lesions.
