Which of the following diagnostic tests should be performed annually over age 50 to screen for colon cancer?
A. Abdominal CT scan
B. Abdominal x-ray
C. Colonoscopy
D. Fecal occult blood test
Correct Answer: D. Fecal occult blood test
Surface blood vessels of polyps and cancers are fragile and often bleed with the passage of stools. A fecal occult blood test is used to find blood in the feces, or stool, which can be a sign of polyps or cancer. A positive test, meaning that blood is found in the feces, can be from causes other than a colon polyp or cancer, including bleeding in the stomach or upper GI tract and even eating rare meat or other foods. There are 2 types of tests: guaiac (FOBT) and immunochemical (FIT). Polyps and cancers do not bleed continually, so FOBT must be done on several stool samples each year and should be repeated every year. Even then, this screening test provides a fairly small reduction in deaths from colorectal cancer, around 30% if done yearly and 18% if done every other year.
Option A: Abdominal CT scan can help establish tumor size and metastasis. Ct colonography, sometimes called virtual colonoscopy, is a screening method being studied in some centers. It requires interpretation by a skilled radiologist to provide the best results. A radiologist is a doctor who specializes in obtaining and interpreting medical images. CT colonography may be an alternative for people who cannot have a standard colonoscopy due to the risk of anesthesia, which is medication to block the awareness of pain, or if a person has a blockage in the colon that prevents a full examination.
Option B: Abdominal x-ray is a commonly performed diagnostic x-ray examination that produces images of the organs in the abdominal cavity including the stomach, liver, intestines, and spleen. When an abdominal x-ray is performed to provide pictures of the kidneys, ureters, and bladder, it’s called a KUB x-ray.
Option C: A colonoscopy can help locate a tumor as well as polyps, which can be removed before they become malignant. A colonoscopy allows the doctor to look inside the entire rectum and colon while a patient is sedated. A flexible, lighted tube called a colonoscope is inserted into the rectum and the entire colon to look for polyps or cancer. During this procedure, a doctor can remove polyps or other tissue for examination. The removal of polyps can also prevent colorectal cancer.
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