Colon Cancer; Diagnosis.

Because the symptoms of colon cancer are vague and typically occur late in the development of the cancer, a variety of tests are used to both screen and diagnose the disease. Screening tests look for disease in those who look and feel healthy, ideally catching the disease as early as possible or in the case of colon cancer, even before the precancerous lesion has turned into cancer. Diagnostic tests look for the cause and determine the extent of the disease in someone who has obvious symptoms.

A bowel prep is often required in preparation for many of these tests, especially a colonoscopy. This involves cleaning out your bowel the night before the test with a prep solution such as "GoLYTELY." It is important that the bowel be clean so the physician performing the colonoscopy or barium enema gets the best look at your colon. Since some preps can affect your blood level for certain electrolytes, your health care professional will tell you which prep to use for your procedure.

Diagnostic Tests

Flexible sigmoidoscopy or colonoscopy. If a mass or any other types of abnormal areas are seen through the flexible sigmoidoscope or colonoscope, a sample (biopsy) is taken for further examination by a pathologist to determine if it's cancerous or benign.

Complete blood count (CBC) and blood chemistry. The CBC determines whether you are anemic because many people with colorectal cancer become anemic due to prolonged bleeding from the tumor. This test is also performed on a regular basis in people receiving chemotherapy because these drugs temporarily affect blood-forming cells of the bone marrow.

Carcinoembryonic antigen blood test (CEA) . The CEA blood test is a marker for colon cancer used to check for cancer in people who have already been treated for colorectal cancer. Not all colon cancers increase CEA blood levels, but it can provide an early warning of a cancer that has returned.

Ultrasound. This test uses sound waves reflected off the tissues of nearby organs and converted by computer into images to help your health care professional see if any mass exists. Ultrasound may be used to look at your liver or inside your bowel for tumors.

Computed tomography (CT) . In this test, a rotating X-ray beam creates a series of pictures of the body from many angles, helping visualize any masses.

Magnetic resonance imaging (MRI) : Like CT, magnetic resonance imaging displays a cross-section of the body. However, MRI uses powerful magnetic fields and radio waves instead of radiation. MRI is used to examine the liver or to stage rectal cancer.

Chest x-ray. This familiar imaging test detects if colorectal cancer has spread to the lungs.

PET scanning: This test can determine if certain cells are using glucose more than other cells. Cancer cells, which are actively dividing, use more glucose so they light up on a PET scan. This test is used to follow cancer and can be combined with a CT scan to better localize a possible recurrence. It is important to remember that not all tumors will be responsive to PET/CT imaging.

Colorectal Cancer Stages

As with all cancers, there are various stages of colon cancer:

Stage 0: Abnormal (dysplastic) cells have been found in the innermost lining (mucosa) of the colon. This stage is also known as carcinoma in situ or intramucosal carcinoma, and there is a very small chance these cells will spread, so this stage is not considered to be invasive cancer.

Stage I: Cancer has spread to the inside lining of the colon but not to the outer walls.

Stage II: Cancer has spread through the colon or rectum and may invade surrounding tissue, but no lymph nodes are involved.

Stage III: Cancer has spread to the lymph nodes, but not to distant sites.

Stage IV: Cancer has spread to other distant parts of the body, such as the liver or the lung.

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Keywords: colon cancer, colorectal cancer, screening tests, diagnostic test, fecal occult blood test, digital rectum examination, barium enema, colonoscopy, genetic testing