Diagnostic Tests for Colorectal Cancer
The Colorectal Cancer Center uses the expertise of its physicians and a variety of procedures to diagnose colorectal cancer and identify the stage of the disease.
Most colon and rectal cancers are discovered through either a colonoscopy or barium enema. In the future, virtual colonoscopy may be useful in the diagnosis of colon cancer. Once the diagnosis has been made, it is important to determine the stage of the disease. The stage will have an impact on the cancer's treatment. Tests are conducted to learn if cancer cells have spread through the colon or rectal wall to tissues around it or other parts of the body. These tests could include CT scan, transrectal ultrasound or PET scan.
In this procedure, a technologist inserts a lubricated enema tip into the patient's rectum and allows liquid barium to flow through the enema tip a little at a time. The technologist then takes a series of X-ray pictures of the colon. The exam takes approximately 45 minutes. A patient prepares for the test by drinking a special prep and only clear liquids the day before.
CT scans are special X-rays that are analyzed by a computer, giving cross-sectional images of the body. The abdomen and pelvis are usually checked by these computerized scans when colon or rectal cancer has been diagnosed. These are used to evaluate the extent of other organ involvement, especially the liver, which helps stage the cancer and guide therapy.
Transrectal ultrasound is a diagnostic, painless exam that is performed after a rectal tumor is diagnosed. It is a 15-minute outpatient procedure. A slender, lubricated probe is placed into the rectum. High-frequency soundwaves echo off the suspected rectal tumor and give a picture of the rectum and anything present in it. It helps stage the rectal cancer and guide therapy. To prepare, patients need two enemas a few hours prior to the procedure. No other preparation is required. Patients are free to go back to normal activities after the test is complete.
PET scans are very sensitive detectors of metabolic activity in cancer cells. A PET scan is a test that uses small doses of chemicals called radionuclides attached to a sugar. After this is injected into the patient, the PET scanner detects positron emissions given off by the radionuclide. Malignant tumors grow at a faster rate than normal tissue and use more sugar, so they appears as a higher number on the scan. These are quick and painless and can assess the whole body for tumor spread or recurrence, or can monitor the success of therapy.