Screening
Colorectal screening allows doctors to find and remove polyps (small areas of tissue that can become cancerous), as well as discover colorectal tumors at an early stage, rather than waiting for symptoms to occur.

General guidelines for colorectal screening are as follows:

• Colonoscopy every 10 years, beginning at age 50
• Annual fecal occult blood test (described below), preferably combined with sigmoidoscopy every five years.

City of Hope recommends patients talk with their physician about when to begin screening for colorectal cancer. A colonoscopy may be advisable more frequently for individuals with polyps, inflammatory bowel disease, previous colorectal cancer and family members with colon cancer.

Diagnosing
Several different types of tests are used to examine the colon, rectum and stool for evidence of colon cancer, including:

• Physical exam and history
• Fecal occult blood test Small samples of stool are placed on chemically treated cards and examined for the microscopic presence of blood.
• Digital rectal exam A doctor inserts a lubricated, gloved finger into the rectum to feel for lumps or abnormal areas.
•  Barium enema (also known as a lower GI series) For this examination, a liquid containing barium is placed into the rectum, which makes the colon and rectum easier to see in an X-ray.
• Sigmoidoscopy In this test, a sigmoidoscope (a thin, lighted tube) is inserted through the rectum into the sigmoid colon. During the procedure, polyps or tissue samples may be removed for biopsy.
• Colonoscopy A colonoscopy allows doctors to examine the entire colon and rectum for polyps, abnormal areas or cancer. In this test, a colonoscope (a thin, lighted tube) is inserted through the rectum into the colon and polyps or tissue samples may be taken for biopsy. Some colon polyps can be removed entirely during this procedure, which is performed under sedation.
• Biopsy Tissue samples are examined under the microscope to determine what types of cells are present.
• Virtual colonoscopy Also called colonography or CT colonography, this procedure uses a series of X-rays to create detailed pictures of the colon. The images are combined by computer in a process called computed tomography, or CT, to create detailed two- and three-dimensional images that can reveal polyps and other abnormalities inside the colon.