An Overview of Rectal Cancer

Symptoms, Causes, Screening, and Treatment

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The rectum is the last 6 inches of the large intestine. Like other organs in the body, the rectum is vulnerable to many diseases and conditions, including cancer. Rectal cancer is a type of cancer that develops in the rectum.

This article will discuss what rectal cancer is and its symptoms. It also covers the causes, diagnosis, treatment, and screening of the disease.

What Is Rectal Cancer?

Rectal cancer differs from ​anal cancer, which refers to cancers that are in the region between the rectum and the outside of the body. The terms "colon cancer" and "colorectal cancer" are often used interchangeably, so much of the information that you will see about colon cancer pertains to rectal cancer as well.

However, rectal cancer is different from cancer that is found higher up in the colon, especially when it comes to treating the disease with surgery. It is estimated that rectal cancer caused 43,340 deaths in 2020.

rectal cancer: newly diagnoses cases
Illustration by Verywell

What Are The Symptoms of Rectal Cancer?

In its 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: This is often bright red versus blood in the stool that's related to cancers that are higher in the colon. Blood due to those types of cancers can appear dark red or black.
  • Digestive issues: Persistent constipation, diarrhea, or other bowel changes can be symptoms.
  • Thinner stools: Stools that are described as "pencil-like" or thin may occur when a tumor in the rectum obstructs part of the canal.
  • Unexplained weight loss: Unintentional weight loss is defined as the loss of at least 5% of body weight over a six-month to 12-month period and can be a symptom of rectal cancer.
  • Abdominal discomfort: This may include pain, tenderness, or cramping.
  • Generalized fatigue: You feel more tired than usual, even if you're sleeping well. 
  • Anemia: When rectal cancer causes chronic, light bleeding, the first symptom may be anemia or symptoms related to anemia, such as lightheadedness, fatigue, or pale skin.

Rectal Cancer Causes and Risk Factors

Scientists don't know exactly what causes rectal cancer, but they do know what increases a person's risk of developing it. Risk factors for rectal cancer include:

  • Age: Being older than 50
  • Family or personal history of colon cancer: It's thought that 25% of colon cancers have a genetic link. However, 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.
  • Personal history of some types of colon polyps (small growths in the colon)
  • Smoking: Either currently or in the past

Screening and Diagnosis

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

  • Colonoscopy: A colonoscopy allows the healthcare provider to get an in-depth view of the colon with a colonoscope, a fiber-optic tube attached to a microscopic camera that transmits live video to a monitor. The colonoscope is gently inserted into the anus and slowly into the colon, giving the healthcare provider 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.
  • Fecal occult blood test: A fecal occult blood test (FOBT) can detect blood in your stool that you may not see with the naked eye or confirm that it is actually blood in the stool that you may have seen. You are given a special kit to collect stool samples. Two similar tests are the fecal immunochemical test (FIT) and a stool DNA test (Cologuard).

For adults who are at average risk of developing colon or rectal cancer, it is recommended to begin getting screened at age 45. Adults who are at a higher risk of developing the disease may need to begin screening at an earlier age based on the recommendation of their healthcare provider.

Remember, even if you are not experiencing any symptoms of rectal cancer, you should always follow your healthcare provider's screening recommendations. If a screening test reveals suspicious results, then a colon biopsy is done.

A colon biopsy can be done during a colonoscopy or surgery. During a colon 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, imaging studies such as a CT scan, magnetic resonance imaging (MRI), and endoscopic ultrasound help to assign a clinical stage, which is critical to determining the course of treatment.

Surrounding lymph nodes are tested and may also be removed during the surgery. Further testing may be done to see whether the cancer has metastasized or spread. 

rectal cancer: stage at diagnosis
Illustration by Verywell

How Rectal Cancer Is Treated 

The treatment for rectal cancer will depend on the stage of the disease, as well as other factors such as the particular location of the tumor(s) and your general health.


In the early stages of rectal cancer, surgery may be the only treatment needed. Several surgical methods can be used to remove cancerous rectal tissue.

The type of surgery that's chosen depends on the patient's general health, the stage of the rectal cancer, and the location of the tumor(s). For those who are not good candidates for surgery, radiation therapy may be an option, but it is usually not as effective.


Chemotherapy is used to treat rectal cancer when the tumor has spread to nearby lymph nodes and/or has invaded the wall of the bowel. The organs in the 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, which is also called a tumor.

Chemotherapy drugs work by eliminating these rapidly multiplying renegade cells. Chemotherapy for rectal cancer may be prescribed either before or after surgery and may also be given in conjunction with radiation therapy.

Radiation Therapy

Another treatment option for rectal cancer, this type of therapy uses certain types of high-energy radiation beams to shrink tumors and eliminate cancer cells. Radiation therapy works by damaging a cancer cell's DNA, leading to cellular death. It may also be given in conjunction with chemotherapy.


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 long before they turn cancerous. 

Avoiding risk factors for colon cancer can also reduce your chances of developing the disease. Eating a balanced diet is important, as well as maintaining a healthy weight and quitting smoking.


Rectal cancer occurs in the rectum, the last six inches of the large intestine. People with rectal cancer in its early stages usually don't have symptoms, sometimes for years. As the disease progresses, they may develop blood in the stool, digestive issues, unexplained weight loss, anemia, and other issues.

Being older than 50, smoking, and having a family history of colon cancer are all risk factors for rectal cancer. Treatments for rectal cancer include surgery, chemotherapy, and radiation therapy.

Regular colon screening is essential for rectal cancer prevention. If you're at an average risk, it's recommended to begin getting colonoscopies at age 45.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American Cancer Society. Key statistics for colorectal cancer.

  2. American Cancer Society. Colorectal cancer signs and symptoms.

  3. American Cancer Society. Colorectal cancer risk factors.

  4. American Cancer Society. Colorectal cancer screening tests.

  5. American Cancer Society. Surgery for rectal cancer. Revised February 21, 2018.

  6. American Cancer Society. Chemotherapy for colorectal cancer. Revised February 21, 2018.

  7. American Cancer Society. Can colorectal cancer be prevented? Revised: May 30, 2018.

Additional Reading

By Lisa Fayed
Lisa Fayed is a freelance medical writer, cancer educator and patient advocate.