To confirm the diagnosis and to localize the tumor when colon cancer is suspected, either a lower GI series (barium enema x-ray) or colonoscopy is performed.
Taking x-rays of the colon a barium enema involves and the rectum after the patient is given an enema with a white, chalky liquid containing barium. The barium outlines the large intestines on the x-rays. Tumors and other abnormalities appear as dark shadows on the x-rays. For more information, please read the Lower Gastrointestinal Series (Barium Enema) article.
For the purpose of inspecting the inside of the entire colon colonoscopy is a procedure where by a doctor inserts a long, flexible viewing tube into the rectum. Colonoscopy is generally considered more accurate than barium enema x-rays, especially in detecting small polyps. If colon polyps are found, they are usually removed through the colonoscope and sent to the pathologist. The pathologist examines the polyps under the microscope to check for cancer. While the majority of the polyps removed through the colonoscopes are benign, many are precancerous. Removal of precancerous polyps prevents the future development of colon cancer from these polyps. For more information, please read the Colonoscopy article.
During colonoscopy if cancerous growths are found, small tissue samples (biopsies) can be obtained and examined under the microscope to confirm the diagnosis. Staging examinations are performed to determine whether the cancer has already spread to other organs if colon cancer is confirmed by a biopsy. Since colorectal cancer tends to spread to the lungs and the liver, staging tests usually include chest x-rays, ultrasonography, or a CAT scan of the lungs, liver, and abdomen.Sometimes, the doctor may obtain a blood test for CEA (carcinoembyonic antigen). CEA is a substance produced by some cancer cells. Especially when the disease has spread.It is sometimes found in high levels in patients with colorectal cancer.
