Rectal cancer is cancer in the rectum, the last part of the large intestine. It allows waste to pass to the anus and out of the body.

Cancer occurs when cells in the body divide without control or order. If cells keep dividing, a mass of tissue (a growth or tumor) forms. The term cancer refers to malignant tumors. They can invade nearby tissue and spread to other parts of the body.


The cause is unknown.

Risk Factors

Research shows that certain risk factors are associated with the disease, including:

  • Age: 50 or older
  • Hereditary conditions (eg, familial polyposis or lynch syndrome)
  • History of colon or rectal cancer or polyps
  • Family history of colorectal cancer, especially a parent, sibling, or child
  • Radiation therapy for prostate cancer
  • Obesity
  • Diet high in fat and low in fiber
  • Smoking
  • Heavy alcohol intake


Rectal cancer often does not have any symptoms. Some symptoms associated with it include:

  • Blood (bright red or very dark) in the stool
  • A change in bowel habits, such as diarrhea, constipation, or the bowel does not empty completely
  • Stools have a different shape than usual (eg, narrower)
  • Abdominal discomfort (gas pains, bloating, fullness, and/or cramps)
  • Change in eating habits
  • Unexplained weight loss
  • Frequently feeling tired or run down

These may also be caused by less serious health conditions. See a doctor if you have these symptoms.


The doctor will ask about symptoms and medical history and do a physical exam.

Screenings for cancer or precancerous polyps include:

  • Digital rectal exam—the doctor's gloved finger will examine the rectum for lumps or growths
  • Fecal occult blood test—a test to check for hidden blood in the stool
  • Colonoscopy—examination of the rectum and colon using a lighted tube called a colonoscope
  • Sigmoidoscopy—examination of the lower colon using a lighted tube called a sigmoidoscope
  • Barium enema—rectal injection of barium coats the lining of the colon and rectum; done before x-rays to create better images of the lower intestine
  • CT colonography—radiology test that looks at your large intestines

Additional tests may confirm the presence of cancer, determine what stage the cancer is in, and/or determine if the cancer has spread:

  • Biopsy—removal of tissue to test for cancer
  • Polypectomy—removal of a polyp during a sigmoidoscopy or colonoscopy
  • Blood tests to look for anemia and cancer markers in the blood
  • CT scan—x-ray that uses a computer to make pictures of structures inside the body; identifies the spread of the tumor
  • Positron emission tomography (PET)—produces images showing the amount of functional activity in tissue; shows if the disease has spread outside the pelvis
  • Transrectal ultrasound—an ultrasound probe inserted into the rectum sends out sound waves to image the tumor


Treatment will depend on the stage of the cancer, the spread into the wall of the rectum, and your overall health. Options include:


Surgery is the main treatment. The tumor and nearby rectal tissue are removed. It may also involve nearby lymph nodes. The surgery may be done by:

  • Laparoscopy—This is for the removal of early stage cancer.
  • Open surgery—This is used to remove larger, later stage tumors, nearby healthy tissue, and potentially nearby lymph nodes. The doctor will look for additional cancer in the colon.

Sometimes, nearby healthy rectal or colon tissue will be removed. This is called colectomy. Healthy tissue is removed in case the cancer has spread. Often, the remaining healthy portions of the colon and rectum are reconnected. Sometimes, the end of the healthy colon is temporarily or permanently attached to an opening in the abdomen called a colostomy. It allows body waste to pass out of the body if the colon cannot do so.

Radiation Therapy

Radiation is used to kill cancer cells and shrink tumors. It is directed at the site of the tumor from a source outside the body. This therapy is aimed at the immediate area of the cancer. It is used alone or with chemotherapy.


This therapy uses drugs to kill cancer cells. It may be given in many forms, including pill, injection, and via a catheter. Drugs enter the bloodstream and travel through the body killing cancer cells. They can also kill healthy cells. This therapy is systemic, meaning it affects your entire body.

Combined chemotherapy and radiation therapy has been the preferred treatment.

If you are diagnosed, follow your doctor's instructions.


The cause of most rectal cancer is not known. Many colon and rectal cancers can be prevented by finding and removing polyps that could become cancer. Beginning at age 50, both men and women at average risk for colon and rectal cancer should follow one of these five screening options:

  • Yearly fecal occult blood test or fecal immunochemical test
  • Colonoscopy every 10 years
  • Flexible sigmoidoscopy every five years
  • Double contrast barium enema (x-rays of the colon and rectum) every five years
  • CT colonography every five years
Discuss these cancer screening tools with your doctor to see which option is best for you.

People with any of the following risk factors should begin colon and rectal cancer screening earlier (at age 40) and/or undergo screening more often:

  • Strong family history of colorectal cancer or polyps
  • Family history of hereditary colorectal cancer syndromes
  • History of colorectal cancer or adenomatous polyps
  • History of chronic inflammatory bowel disease