Colorectal Cancer Diagnosis

Over 95% of colon and rectal cancers are adenocarcinomas, a type of cancer of the cells that are on the inside lining of the colon and rectum. Polyps form on the lining and lead to cancer. Colon cancer can be prevented if these polyps are detected and removed. Recently, screening methods have been recommended for people without symptoms to try to find either the polyps or early signs of cancer. In many cases, screening tests can find colorectal cancers at an early stage and greatly improve the chances of successful treatment. Beginning at age 50, men and women who are at average risk for developing colorectal cancer should begin screening.

Screening tests include:

  • Physical exam - as a part of a routine visit to the physician
  • Fecal occult blood test - take home kits that test multiple stool samples
  • Sigmoidoscopy/colonoscopy - an X-ray procedure in which a scope is inserted inside the colon to look for changes or polyps that might be a precursor of cancer
  • Barium enema - an X-ray procedure that takes pictures of the colon

Many colon cancers have no symptoms. Hidden blood in the stool is often the only warning sign of colon cancer. The following symptoms can be associated with colon and rectal cancer:

  • Change in bowel habits such as diarrhea, constipation, or narrowing of the stool that lasts for more than a few days
  • Feeling that you need to have a bowel movement that doesn't go away after doing so
  • Loss of weight
  • Constant tiredness
  • Bleeding from the rectum or blood in the stool
  • Cramping or tenderness in the abdomen
  • Unexplained low blood counts
  • Bowel obstruction

If colon cancer is suspected, further tests are ordered to find out if the disease is really present and to see if it has spread. A biopsy procedure, which may be done as a part of a colonoscopy, can determine if cancer is present. The physician may order a series of blood tests to look for substances like CEA and CA-19-9 that are made by colon and rectal cancer cells and released into the blood stream. In cases of suspected or known colon cancer, the physician may also order a CT scan to show the structure of the organs and tissues in the abdomen. While these tests can provide information regarding the size and location of the primary tumor and may be able to detect other abnormalities that may represent the spread of the disease, they cannot tell if the abnormalities are benign or cancerous.

PET/CT scanning is an important addition to other tests that can be done right after you are diagnosed with cancer of the colon or rectum.

Source: American Cancer Society. Cancer Facts & Figures 2011. Atlanta: American Cancer Society; 2011