Colorectal Cancer Symptoms: What You Need to Know

Colorectal cancer can be hereditary, which may be a cause for concern for individuals unsure about their risk of developing this cancer. But there are other risk factors that people should know about that may clue them in about their chances of having colorectal cancer.

When you reach out to your provider, bring up your initial concerns, observations and any possible risk factors so that you can have the most effective visit with your provider possible.

Being Aware of Colorectal Cancer Symptoms

In some cases, colorectal cancer causes no symptoms in early stages, which makes screening even more important. But when symptoms occur, they can include:

• Abdominal pain or cramping
• Blood in the stool, which might turn the stool a dark brown or black color
• Changes in bowel habits, such as constipation, diarrhea or narrowing of stool lasting for more than a few days
• Fatigue and weakness
• Feeling like you need to have a bowel movement even after having one
• Rectal bleeding, especially with blood that is bright red
• Unintentional weight loss
  

It’s important to remember that many of these symptoms can be caused by conditions other than cancer, such as irritable bowel syndrome or hemorrhoids. Make an appointment with your doctor if you experience any of these signs so you can get to the bottom of what’s causing them.

Waiting to act until symptoms show up is not ideal, so speak with your provider to determine if you may have risk factors for colon cancer. As 90% of colon cancer arises from adenomatous polyps, it is preventable if these polyps are removed before they turn into cancer.

Do You Have Risk Factors?

Although everyone should begin screening for colorectal cancer eventually, if you have risk factors, your doctor may recommend starting screening earlier. 

According to the American Cancer Society, people at average risk of colon cancer should begin regular screenings at age 45. Previous guidelines recommended screening begin at age 50, but the age was lowered due to a recent rise in colorectal cancer diagnoses in younger people. The increase in the incidence of colon cancer among the younger population is due to many factors but is strongly associated with the increased incidence of youth obesity. 

However, if you are at higher risk, your doctor may recommend beginning screening earlier than age 45 and getting screened more often. How do you know if you are at higher risk for developing colon or rectal cancer? Risk factors include having:

• A strong family history of colorectal cancer, meaning you have a parent, sibling or child diagnosed with colorectal cancer or pre-cancerous adenomatous polyps, which can turn into cancer. The risk is higher if the diagnosis occurred before age 50. 
• Inherited gene mutations, such as Lynch syndrome
• Inflammatory bowel disease, such as ulcerative colitis or Crohn’s disease
• A previous diagnosis of colorectal cancer or adenomatous polyps 

Other risk factors include:

• A diet high in red or processed meats
• Being overweight or obese
• Lack of physical activity
• Moderate to heavy alcohol use
• Smoking

Talk to your doctor about your personal risk factors. They will determine the appropriate age for you to begin screening, as well as the best type of screening for you and how often to have it done.

How Is Screening Performed?

There are several tests that may be used to screen for colorectal cancer, including:

• Colonoscopy: Colonoscopies are considered the gold standard of colorectal cancer screening tests and offer the most comprehensive view of the colon and rectum. For this exam, you must fast and do bowel prep at home to completely empty your bladder and rectum. Before the exam, you’ll likely be given a sedative. The doctor will insert a colonoscope into the rectum and up into the colon, carefully examining the inner walls of the colon. If small polyps are found, they can be removed immediately and sent to a lab for testing. If larger polyps or other abnormal areas are found, the doctor will remove a piece to send for testing.
• CT colonography: Also called a virtual colonoscopy, this is an advanced type of CT scan that takes 3D pictures inside the colon. It requires the same bowel prep as a colonoscopy but doesn’t require sedation and uses a low dose of radiation.
• Colon capsule endoscopy: Now approved for patients who can’t get a colonoscopy. After receiving the bowel prep, the patient swallows a capsule with two cameras located at each end. These cameras take pictures of the colon while passing through. 
• Fecal immunochemical test (FIT): This is a stool test that looks for occult, or hidden, blood in the stool and requires collecting samples at home. No special prep is necessary. But if blood is found in the stool, your provider will order a colonoscopy to determine the cause.
• Guaiac-based fecal occult blood test: This stool test also checks for hidden blood in the stool, but unlike the FIT test, this one uses a chemical reaction. You will need to make certain dietary changes before you can take this blood test.
• Stool DNA test: Also called a FIT-DNA test, a stool DNA test looks for not only hidden blood but also abnormal DNA from cancer or polyp cells. You’ll receive a kit to perform the test at home, and no dietary restrictions are required.  

Additional Tests and Diagnosis 

Your doctor will perform tests to determine if your symptoms may be caused by cancer or if additional testing is necessary. These include:  

• Blood tests: Your doctor might order a complete blood count to measure different types of cells and determine whether you have anemia, which can be a sign of colorectal cancer. Other tests can check for tumor markers in the blood or liver enzymes to determine if cancer has spread to the liver. 
• Stool tests: If you have anemia or other symptoms that could indicate colorectal cancer, your doctor might order stool tests to check for occult blood. These tests require you to collect stool samples at home and bring them to your doctor’s office for testing. 
• Diagnostic colonoscopy: This is performed the same way as a screening colonoscopy but is ordered if you’re having symptoms or anything abnormal was already found, such as blood in the stool. 
• Proctoscopy and flexible sigmoidoscopy: This is a rectal exam done if your doctor suspects rectal cancer. The doctor inserts a thin, lighted tube with a small camera on the end into the anus to view the inside lining of the rectum and the sigmoid colon.
• Imaging tests: Certain imaging tests can be useful to get a close look at any suspicious areas or to determine whether cancerous cells have spread. These tests might include CT scans, ultrasounds and MRI scans.

More to Read

• Do I Need to Be Screened for Colorectal Cancer?
• What You Should Know About Genetic Testing for Cancer
• 7 Dietary Recommendations That Will Reduce Your Risk of Cancer
• Are You At Risk for Colon Cancer?

Medically reviewed by Cherif Boutros, MD.