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Rectal cancer

Overview of rectal cancer

Rectal cancer is cancer that starts in the rectum, specifically the last 6 inches of the large intestine. It is a form of colorectal cancer. Rectal cancer starts as noncancerous polyps, which gradually (over 10 to 15 years) become cancerous. If you’re an adult living in the United States, your risk of rectal cancer is 5 percent during your lifetime.

At Dignity Health, we’re dedicated to offering comprehensive care for the prevention, screening, diagnosis, and treatment of rectal cancer. If you’d like to learn more, Find a Doctor near you.


It’s important to understand that signs and symptoms of rectal cancer can be similar to those of other conditions. Noticing these signs or symptoms does not guarantee that you will be diagnosed with rectal cancer, but they are often cause for concern.

Be sure to consult with your doctor if you have any of the following symptoms:

  • Very bright red or dark red blood in your stool
  • Changes in your bowel habits, such as diarrhea, narrowing of your stool, not feeling like your bowel is emptying completely, and constipation
  • Changes in your appetite
  • Dizziness, fatigue, or a fluttering heartbeat
  • Anemia
  • Losing weight
  • Feeling fatigued
  • Abdominal discomfort
  • Rectal bleeding

If you or a loved one would like to discuss possible symptoms of rectal cancer, talk with a doctor at Dignity Health.


Rectal cancer is caused by the abnormal growth of cells in the lower digestive tract between the anus and lower part of the colon.

Cancer occurs when there is growth of abnormal cells. Without treatment, these cells may multiply and grow further, causing tumors and eventually spreading throughout the body. Research is ongoing, but experts still do not fully understand why cancer occurs in some people and not others. There are some risk factors however, such as age, genetics, and physical fitness level.


The vast majority of cases of rectal cancer are called adenocarcinoma.

Some rectal cancers are inherited, meaning that they result from genes passed down through families. If many people in your immediate family have been diagnosed with rectal cancer, speak with your doctor about whether you should consider genetic testing.

Less often, cancers such as lymphoma (which typically begins in the lymph nodes), carcinoids (which begin in the hormone-producing cells), and soft-tissue sarcoma (which can start throughout the GI tract, but rarely is first observed in the rectum) can also cause rectal cancer.

Risk factors

Researchers don’t yet fully understand the causes of rectal cancer. However, there are several known risk factors. Understanding them may help you prevent the disease or receive an early diagnosis.

You are more likely to develop rectal cancer if you have any of the following risk factors:

  • Being African American
  • Age 50 or older
  • Specific gene mutations or genetic conditions linked to the disease
  • A family or personal history of cancer or colorectal polyps
  • A history of inflammatory bowel disease (IBD) or ovarian, uterine, or breast cancer
  • Type 2 diabetes

Also, your lifestyle choices can affect your risk of rectal cancer. These factors include:

  • Smoking cigarettes or cigars
  • Drinking alcohol
  • Being very overweight (obese)
  • Eating an unhealthy diet
  • Not exercising


Our oncologists at Dignity Health will encourage you to get regular screenings for rectal cancer. These preventive exams can help your doctor find precancerous polyps and diagnose rectal cancer at an earlier stage before it spreads. As with all types of cancer, the earlier it is found, the more likely that treatment will be effective.

If you have immediate family members (such as siblings, parents, grandparents, or children) who have been diagnosed with rectal cancer, speak with your doctor about whether you should consider genetic testing.

In addition, you can lower your risk by:

  • Not smoking, or quitting smoking as soon as possible
  • Eating a healthy diet high in vegetables and sources of healthy omega-3 fats, such as fish
  • Exercising regularly, as recommended by your doctor
  • Avoiding excessive alcohol consumption
  • Maintaining a healthy weight

The information contained in this article is meant for educational purposes only and should not replace advice from your healthcare provider.