Colon and Rectal Cancers - Diagnosis

A study published in April 2004 in the Journal of the American Medical Association (JAMA) compared results of standard colonoscopy versus virtual colonoscopy in over 600 patients at nine major medical centers. Virtual colonoscopy had much lower rates of successfully finding polyps than standard colonoscopy. Virtual colonoscopy detected polyps of at least 6 mm in 39% of patients and polyps of at least 10 mm in 55% of patients. By contrast, standard colonoscopy detected 99% of polyps of at least 6 mm, and 100% of polyps of at least 10 mm. In addition, accuracy rates varied widely among the different hospitals. The authors advised that until more improvement in training and technique is achieved, virtual colonoscopy "is not yet ready for widespread clinical application."

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Magnetic Resonance Colonography (MRC). Magnetic resonance colonography (MRC) is another non-invasive technique for visualizing the colon. The patient receives an enema containing a contrast agent, and then magnetic resonance images are taken. MRC is fast, comfortable, and less invasive than colonoscopy. Currently, however, there is a poor detection rate for flat tumors and for polyp tumors less than 10 mm in diameter.

Encapsulated Video Camera. Researchers have developed a video camera that is small enough to be swallowed. It works its way through the digestive tract, beaming data to a receiver worn on the patient's waist, and is excreted in eight to 72 hours. The camera was not designed to replace standard visualization procedures and is currently being used to assess problems in the hard-to-reach small intestine. More testing is needed to determine whether it has value in colon cancer screening as well.