Rectal Cancer

Risk Factors for Rectal Cancer and How it is Diagnosed

film showing rectum lit up in large intesting suggestive of cancer
What is rectal cancer, what are the symptoms, how is it diagnosed, and how is it treated?. Credit: Photo©janulla

What is rectal cancer?  Is it the same thing as anal cancer or colon cancer?  What are the symptoms and how is it treated?

Rectal Cancer - Definition

Rectal cancer is a type of cancer that develops in the rectum, the last six inches of our large intestine. Like other organs in our body, the rectum is vulnerable to many diseases and conditions, such as cancer.  Rectal cancer differs from anal cancer which instead refers to cancers in the region between the rectum and the outside of the body.

  The terms colon cancer and colorectal cancer are often used interchangeably, so that much of the information you will see about colon cancer pertains to rectal cancer as well.  Rectal cancer is different, in some important ways, than cancers found higher up in the colon, especially when it comes to surgery for the disease.

Since rectal cancer and cancers higher up in the colon are often lumped together, it's hard to know how high the incidence of rectal cancer really is.  But colon cancer is the 3rd leading cause of cancer deaths in men and the 3rd leading cause of cancer deaths in women in the United States.  This diagram shows the location of the rectum within the large intestine.

Causes and Risk Factors of Rectal Cancer

We can't exactly pinpoint what causes rectal cancer, but we know what may increase our risk of developing it. Risk factors for rectal cancer include:

  • Being older than 50.
  • A family or personal history of colon cancer (a person does not need a family history of colon cancer to have rectal cancer; it is most commonly diagnosed in those without a family history)  It's thought that 25% of colon cancers have a genetic link of some form.
  • A personal history of some types of colon polyps (small growths in the colon.)
  • A history of smoking either currently, or in the past.

Rectal Cancer Symptoms

In the early stages, rectal cancer usually doesn't have symptoms. As the disease progresses, which can take years, symptoms of rectal cancer include:

  • Blood in stool - Blood in stool due to rectal cancer is often bright red, versus blood in stool related to cancers higher in the colon which can appear dark red or black.
  • Persistent constipation, diarrhea, or other bowel changes.
  • Thinner stools - Stools described as "pencil like" or thin stools may occur when a tumor in the rectum obstructs part of the canal.
  • Unexplained weight loss - Unintentional weight loss defined as the loss of 5% of body weight or around 10 pounds over a 6 to 12 month period, can be a symptom of rectal cancer.
  • Abdominal pain, tenderness, cramping, or discomfort.
  • Generalized fatigue.
  • Anemia - When rectal cancer causes chronic light bleeding, the first symptom may be anemia, or symptoms related to anemia such as lightheadedness, fatigue, and pale skin.

Rectal Cancer Screening

Several colon cancer screening methods are highly effective at detecting rectal cancer as well. Colon and rectal cancer screening tests include:

  • Colonoscopy - A colonoscopy allows the doctor to get an in-depth view of the colon with a colonoscope, a fiber optic tube that is attached to a microscopic camera that transmits live video to a monitor. The colonoscope is gently inserted in to the anus and slowly to the colon, giving the doctor a full view of the rectum and large intestine.
  • Sigmoidoscopy - Much like a colonoscopy, a sigmoidoscopy is done with a flexible lighted tube with an attached camera, but it is limited to only the lower part of the colon.
  • Barium Enema - During a barium enema, a doctor inserts liquid barium in to the rectum. X-rays are taken of you laying in several positions. The barium allows the colon to be viewed better on x-rays.
  • Fecal Occult Blood Test - A fecal occult blood test (FOBT) finds blood in your stool that you may not see with the naked eye or confirms that it is actually blood in the stool that you may have seen. You are given a special kit to collect stool samples.

    For adults who are at the average risk of colon and rectal cancer, it is recommended to begin screening at age 50. Adults who are classified at a higher risk may begin screening earlier at the recommendation of their doctor. Remember that even if you are not experiencing symptoms of rectal cancer, you should always follow your doctor's screening recommendations.

    Diagnosing Rectal Cancer

    If a screening test reveals suspicious results, then a colon biopsy is done. A colon biopsy can be done during a colonoscopy or surgically. During a biopsy, small amounts of rectal tissue are removed and then sent to a pathology lab to screen for evidence of cancer. If cancer is present, then the stage of rectal cancer is determined through surgery to remove the cancer. Surrounding lymph nodes are tested and may also be removed during the surgery.

    Further testing may be done to look for spread (metastasis) of the cancer.

    Treatment Options for Rectal Cancer

    Treatment of rectal cancer will depend upon the stage of the disease as well as other factors such as the particular location of the tumor and your general health.

    Surgery - In the early stages of rectal cancer, surgery may be the only treatment needed. There are several surgical methods used to to remove cancerous rectal tissue. The type of surgery chosen depends on general health, stage of rectal cancer and location of the tumor. For those who are not good candidates for surgery, radiation therapy may be an option but is usually not as effective.

    Chemotherapy is also a common treatment method for rectal cancer. The organs in our body are made up of cells that divide and multiply as the body needs them. When these cells continue to multiply unnecessarily, the result is a mass or growth, also called a "tumor."  Chemotherapy drugs work by eliminating these rapidly multiplying renegade cells.
    Chemotherapy for rectal cancer may be prescribed before or after surgery and may also be given in conjunction with radiation therapy.

    Radiation therapy is another treatment method used to treat rectal cancer. This type of therapy uses certain types of high-energy radiation beams to shrink tumors or eliminate cancer cells. Radiation therapy works by damaging a cancer cell's DNA, making it unable to multiply.  In cases of rectal cancer, radiation therapy may be given prior to surgery to help shrink large tumors. It may also be given in conjunction with chemotherapy.

    Colon Cancer Prevention

    Regular colon cancer screening is key to preventing rectal cancer. Screening can identify precancerous growths before they potentially progress into cancer. Keep in mind that it takes years for rectal cancer to develop, so routine screening can detect these changes before they turn cancerous. Remember, for average risk people, colon cancer screening should begin at age 50.

    Avoiding risk factors for colon cancer can also reduce your risk of developing the disease. Eating a balanced diet is important, as what you eat today affects your risk of colon cancer tomorrow.  Not smoking and maintaining a healthy weight are also ways to reduce your risk of not only rectal cancer, but many other conditions as well.


    American Cancer Society. Colorectal Cancer. Updated 01/20/16.

    National Cancer Institute. Rectal Cancer Treatment – for Health Professionals PDQ). Updated 01/29/16.

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