Rectal Cancer

Diagnosis

Physicians at Mayo Clinic use various tools to screen patients for rectal cancer. Some tools also help physicians determine the stage of the disease. This information is used to develop a treatment plan.

A flexible sigmoidoscopy is one of the tools physicians may use to screen for rectal cancer.

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• Flexible sigmoidoscopy — A flexible, slender, lighted tube with a tiny camera is used to examine the rectum and the sigmoid (the last two feet of the large intestine).
• Barium enema — This test allows the physician to evaluate the large intestine with an X-ray. Barium, a contrast dye, fills and coats the lining of the bowel, creating a clear silhouette of the rectum, colon and sometimes a small portion of the small intestine. The rectum appears white; growths show up as dark areas.
• Colonoscopy — This technique allows the physician to view the rectum with a thin, lighted, flexible tube called an endoscope. The endoscope contains a tiny camera. Small polyps may be removed during an exam. Colonoscopy is the best diagnostic tool currently available for rectal cancer. Some patients find the necessary bowel preparation inconvenient and uncomfortable. The examination itself also may include some discomfort, and patients may be given a mild sedative. The exam takes 30 to 60 minutes.
• Endorectal ultrasound — Very high-frequency sound waves are used to produce images of the rectum. The advantages of this procedure are that it is safe and minimizes discomfort. An ultrasound probe is added to an endoscope to obtain the images. Once a patient is diagnosed with rectal cancer, endorectal ultrasound is used to determine the depth of invasion of the cancer and whether the lymph nodes are involved. This information, in turn, helps determine both preoperative and postoperative treatment.
• PET scan — Positron emission tomography is a noninvasive diagnostic tool that takes a different approach from other imaging technologies. Instead of providing a clear picture of the physical structure of organs and tissues, PET scans provide information about chemical activity within the organs and tissues. As a result, they may reveal rectal cancer earlier than other imaging techniques. A PET scan also may be better than other imaging techniques at distinguishing between malignant and benign growths.
• CT colonography — Mayo Clinic has been involved in research of CT colonography since its inception and has performed more CT colonographies than any other institution. Currently, physicians at Mayo Clinic perform about 1,000 such examinations per year.