Colorectal cancer, also known as bowel cancer, colon cancer, or rectal cancer, is any cancer that affects the colon and rectum. Common signs include blood in the stool, diarrhea, or constipation.

The American Cancer Society (ACS) estimates that there will be 106,180 new cases of colon cancer and 44,850 new cases of rectal cancer in the United States in 2022.

Colorectal cancer is the third most common cancer in the U.S. And among cancers that affect all sexes, it is the second leading cause of death.

The incidence varies around the world. It is more common in countries with a higher economic status, but according to a 2021 analysis, it is more likely to affect people with low incomes.

Fatality rates have fallen due to medical advances. And, as the 2021 analysis observes, numbers of diagnoses in people younger than 50 are rising, possibly due to improvements in screening.

Below, learn about the symptoms and treatments of colorectal cancer. Also, find out about the risk factors. A person can take steps to limit some of them.

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Colorectal cancer may not cause symptoms in the early stages. If it does, they may include:

  • changes in bowel habits
  • diarrhea
  • constipation
  • a feeling that the bowel does not empty fully
  • blood in feces that makes it look dark brown or black
  • bright red blood from the rectum
  • abdominal pain and bloating
  • feeling full, even when a long time has passed since a meal
  • fatigue or tiredness
  • unexplained weight loss
  • anemia

If a doctor finds signs of anemia during a routine medical check, they may suggest screening for colorectal cancer. Or, they may diagnose it during routine screening.

Around 40% of people with this type of cancer receive the diagnosis when the disease is in an early stage.

The symptoms can be similar to those of many other health conditions. Anyone with concerns about these symptoms should seek medical advice.

Among people who receive a diagnosis of colorectal cancer after reporting symptoms:

  • 37% have blood in feces or from the rectum
  • 34% have abdominal pain
  • 23% have anemia

Among those who receive the diagnosis after seeking emergency medical care:

  • 57% have a blockage in their bowel
  • 25% have peritonitis, or inflammation of the stomach lining
  • 18% have a perforation, or hole, in their bowel

Some people only notice symptoms in the later stages, when the cancer has spread to the lungs, liver, or other areas. The symptoms can depend on the area affected.

If cancer spreads to the liver, a person may have jaundice, which causes yellowing of the whites of the eyes. If a person has white or light brown skin, it may also appear yellowish.

If cancer affects the lungs, it can cause difficulty breathing or a cough.

The cause of colorectal cancer is unclear, but it likely stems from a combination of genetic and environmental factors.

According to research from 2022, around 70% of cases develop for no clear reason, while 10% seem to result from inherited syndromes, and 20% happen in family clusters.

Some other colorectal cancer risk factors may include:

  • being over the age of 50
  • being male
  • having a low income
  • having a diet low in fiber and high in animal protein, saturated fats, and calories
  • having a diet high in red or processed meats
  • consuming alcohol
  • smoking
  • having low levels of physical activity
  • being overweight or having obesity
  • having inflammatory bowel disease
  • having type 2 diabetes
  • having certain genetic features
  • having had breast, ovary, or uterine cancer
  • having undergone radiation therapy for abdominal cancer in childhood
  • having polyps in the colon or rectum

Polyps are sometimes precancerous. Learn about one type, called sessile polyps, that can develop in the colon.

Increased risk among Black Americans

Research from 2018 concludes that Black Americans are more likely to develop and die from colorectal cancer than any other group of people in the U.S.

As the ACS report, the chance of having this type of cancer is at least 20% higher for Black people than for white people, and the fatality rate is 40% higher for Black people.

The ACS cites socioeconomic factors and inequity in screening and other aspects of healthcare, as well as inequity in employment, diet, and other factors related to daily life.

The authors of the 2018 analysis say that identifying whether colorectal cancer affects Black people in distinct ways requires further research. They add that this type of investigation might lead to more effective treatment.

What is health inequity? Learn more here.

The American College of Physicians recommends regular screening for people who:

  • have a personal or family history of colorectal cancer
  • are Black Americans aged 45 years or over
  • are not Black, over 50, and have an average risk
  • have Crohn’s disease, Lynch syndrome, or adenomatous polyposis

A doctor will recommend a specific screening schedule. For example, they may recommend a stool test every 2 years and a colonoscopy or sigmoidoscopy every 10 years.

People should also be aware of the differences between precancerous lesions and polyps and cancerous polyps.

Everyone aged 50 or older has a risk of developing precancerous lesions or polyps. A colonoscopy is the gold-standard approach to removing these. During the procedure, a doctor can also check for cancerous polyps.

Screening can detect polyps before they become cancerous. It can also detect colon cancer in the early stages, when it is easier to treat.

In 80% of cases, a doctor diagnoses colorectal cancer after performing a colonoscopy because the person has symptoms. Routine screening detects 11% of cases, and 7% of people with colorectal cancer receive a diagnosis after seeking emergency care for sudden abdominal symptoms.

The following are the most common screening and diagnostic procedures for colorectal cancer.


A colonoscopy is the gold-standard diagnostic tool for colorectal cancer. It has a high level of accuracy and can show precisely where a tumor is.

The procedure involves using a long, thin, flexible tool called a colonoscope that contains a light and a camera. It allows the doctor to see the whole colon and rectum. They may remove polyps or take a sample of tissue, a biopsy, for testing during the procedure.

A colonoscopy is painless, but some people take a mild sedative to help them stay calm. A person may also need to drink a laxative fluid to empty colon beforehand.

Bleeding and perforation of the colon wall are rare but possible complications.

Blood stool test

This test checks for blood in a stool sample. Many conditions can cause blood in stool, and a positive result does not necessarily mean that cancer is present.

Stool immunochemistry

Also known as a fecal occult blood test, this checks for hidden blood in the lower colon. It involves using a small kit to collect a stool sample at home.

What are some other causes of rectal bleeding?

Stool DNA test

This test checks for several DNA markers that colon cancer or precancerous polyps shed into stool. A person collects an entire bowel movement at home for testing in a lab. If the result is positive, a colonoscopy is necessary.

It is worth keeping in mind that this test cannot detect every DNA marker of cancer.

Flexible sigmoidoscopy

This procedure involves using a sigmoidoscope, a flexible, thin, lighted tube, to examine the rectum and sigmoid colon — the last part of the colon before the rectum.

The test takes a few minutes and is not painful, but it might be uncomfortable. There is a small risk of perforating the colon’s wall.

Barium enema X-ray

Barium is a contrast dye that can reveal any unusual features on an X-ray. A healthcare professional introduces it into the bowel as an enema.

A doctor may recommend a colonoscopy for closer investigation following a barium enema X-ray.

CT colonography

This produces images of the colon. It is less invasive than a colonoscopy, but if it reveals a mass, the person needs a colonoscopy.

Imaging scans

Ultrasound, CT, or MRI scans can show if cancer has spread to another part of the body.

The “stage” of cancer refers to how far it has spread. Determining the stage helps doctors choose the most appropriate treatment.

There are different guidelines for staging. One set of guidelines is:

  • Stage 0: This is the earliest stage, also known as carcinoma in situ. The cancer is only in the inner layer of the colon or rectum.
  • Stage 1: The cancer has grown through the inner layer of the colon or rectum but has not spread beyond the wall of the rectum or colon.
  • Stage 2: The cancer has grown through or into the wall of the colon or rectum but has not yet reached nearby lymph nodes.
  • Stage 3: The cancer has reached nearby lymph nodes but not other parts of the body.
  • Stage 4: The cancer is present in other parts of the body, such as the liver or lungs.

Sometimes, treatment eliminates the cancer but it comes back in the same area or another one. This is called “recurrent” cancer.

The outlook for someone with colorectal cancer depends on different factors, including their age, their overall health, and the stage of the cancer at diagnosis.

The ACS provides 5-year survival rates. These reflect the likelihood of living for at least another 5 years after the diagnosis, compared with a person who does not have colorectal cancer.

The ACS gives survival rates using these stages:

  • Local: The cancer has stayed in its original location.
  • Regional: The cancer has spread to nearby tissues.
  • Distant: It has reached more distant parts of the body.

This table shows the estimated 5-year survival rates for a person with colon cancer.

Stage5-year survival rate
Stage 1 (local)91%
Stage 2 (regional)72%
Stage 3 (distant)14%

This table shows the estimated 5-year survival rates for a person with rectal cancer:

Stage5-year survival rate
Stage 1 (local)90%
Stage 2 (regional)73%
Stage 3 (distant)17%

Here, learn more about the life expectancy for people with stage 4 colon cancer.

Colorectal cancer can affect anyone, and it is not possible to prevent it. However, taking some steps may help reduce the risk.


Dietary measures that may help include:

  • eating plenty of fiber, fruits, and vegetables
  • limiting the intake of red and processed meats.
  • opting for healthy fats, such as from avocados, olive oil, fish oils, and nuts, rather than saturated fats

Exercise and weight

Moderate, regular exercise may help lower the risk of colorectal cancer. Exercise can also help reduce the risk of obesity, which is linked with colorectal and other cancers.


Experts have found that taking aspirin may help reduce the risk in some people, but speak with a doctor about this first.


Researchers are investigating the potential for vaccines to prevent colorectal cancer. One option that has been successful in mice is a vaccine that stops polyps from becoming cancerous. This might, one day, benefit people with a high risk.

Colorectal cancer is a leading cause of cancer-related death. Treatment in the early stages can remove cancerous cells and increase the likelihood of a positive outcome.

It is important to take any signs of colorectal cancer seriously. They can also indicate other potentially severe health problems. However, symptoms of this cancer may not appear until the later stages.

Anyone with a risk of developing colorectal cancer should ask a doctor about screening. Having regular screening improves the chances of an early diagnosis.