Rectal Cancer

May 8th, 2013 by Eduardo Krajewski, MD, FACS, FASCRS

There are approximately 150,000 cases of colorectal cancer diagnosed every year in the United States alone. Of these, about 40,000 are cancers of the rectum. Most of these cancers are adenocarcinomas. People can survive and even be completely cured of this malignancy, but early detection is critical.

What is the rectum?

If you want to know about rectal cancer, it helps to know a little bit of anatomy. The rectum is the part of the colon that connects the large intestine to the anus. It is in this area where stool is stored until it is time to have a bowel movement. Like the rest of the colon, the rectum has several layers from the inside out. These are the:

  • Mucosa and submucosa: the inner layers that secrete mucus to help stool pass smoothly
  • Muscularis propia: the middle layer that contains the muscles that move stool forward
  • Serosa: outer layer

The rectum is also surrounded by lymph nodes, and the closest ones are referred to as regional lymph nodes. These play an important role in cancer treatment decisions as we will see later.

What causes rectal cancer?

Typically, the cancer starts as a small pre-cancerous polyp that grows gradually into a cancer. Even though the exact cause is not known there are several known risk factors. These are:

  • Advanced age
  • Smoking
  • Family history of colorectal cancer
  • Diet high in fat
  • Personal or family history of polyps
  • Lack of screening

What are the symptoms of rectal cancer?

It is important to know that rectal cancer often causes no symptoms at all and might only be detected by screening. Some symptoms though could be:

  • Rectal bleeding or blood in the stool
  • Symptoms of anemia (fatigue, shortness of breath, lightheadedness, rapid heartbeat)
  • Intestinal obstruction
  • Change in bowel habit
  • Thin pencil-like stools
  • Feeling of incomplete stool evacuation

How is rectal cancer diagnosed?

Once an abnormality is detected, your doctor does tests to make the diagnosis. One essential element is a tissue biopsy which is usually obtained through colonoscopy. Colonoscopy involves inserting a flexible tube into the anus. The tube has a camera and special devices on the end of it that allow your doctor to cut out part of any suspicious abnormality. This tissue is then sent to a lab to look for cancer cells.

Other tests are done in order to stage the cancer. Staging means determining how far the cancer has advanced in your body, and this helps determine treatment. These other tests are:

  • Computer tomography (CT) scanning of the abdomen, pelvis and lungs
  • Chest x-ray
  • Blood tests

Once all the information is gathered then the cancer is staged. The staging depends on:

  • How far the cancer has invaded the layers of the rectum
  • Whether or not lymph nodes are involved
  • Whether or not the cancer has spread to other parts of the body like the lungs or liver.

Another test that is taken is a CEA (carcinoembryonic antigen) blood test. This test can help your physicians see how well your body is responding to treatment.

How is rectal cancer treated?

The cancer treatment depends on the stage. For example, a Stage I cancer that has not passed through to the serosa can usually be treated with surgery alone. If lymph nodes are involved, however, a combination of surgery and chemotherapy is often recommended. In some cases, radiation therapy might also be used.

(The details of colorectal cancer treatment and outcomes can be found in another article dedicated specifically to treatment options.)


Rectal cancer is one of the most common of the colorectal cancers. Early detection is essential as survival is improved when the cancer is caught at an early stage. Staging depends on how far the cancer has advanced, and this also determines treatment.

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