Is Your Constipation a Sign of Colon Cancer?

Man with stomach pain
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Constipation is a very common problem, so you are not alone if you (or a loved one) is experiencing it. Also, to ease your mind, know that most people with constipation do not have colon cancer.

However, it's important to get to the root cause of your constipation—don't just ignore it, as in the event that there is something more serious going on (like colon cancer or another underlying health condition), a diagnosis sooner than later is always better.

Understanding Constipation

While constipation has traditionally been described as having less than three bowel movements per week, experts have recommended moving beyond this definition. This is mostly because constipation has unique meanings for different people.

For instance, some people have daily bowel movements, but they describe constipation as chronic straining or a sensation of incomplete evacuation of the stool. 

Now doctors mostly use a set of criteria called the Rome criteria to diagnose constipation. With this criteria, a person must have at least two of the following symptoms for the past three months:

  • Straining during at least 25 percent of bowel movements
  • Lumpy or hard stools in at least 25 percent of bowel movements
  • Sensation of incomplete evacuation for at least 25 percent of bowel movements
  • Sensation of obstruction/blockage (in your bottom) for at least 25 percent of bowel movements
  • Manual maneuvers to remove stool at least 25 percent of the time (for example, using your finger to remove stool)
  • Fewer than three stools a month

In addition, according to this criteria, a person should not have loose stools (unless they use laxatives), and they cannot have a diagnosis of irritable bowel syndrome.

Causes of Constipation

The colon (large intestine) controls the formation and passage of stool from the body by absorbing water out of the solid waste and moving the waste to the rectum and anus.

So anything that changes the colon's ability to regulate the amount of water in stool or that affects the muscles and nerves of the colon that are responsible for moving waste toward the rectum and anus can lead to constipation.

With that, there are a variety of reasons why constipation occurs. Common causes of occasional, "garden-variety" constipation that many people experience from time to time, include:

  • Not eating enough dietary fiber
  • Not drinking enough water and other liquids
  • Lack of exercise
  • Ignoring the urge to defecate until a more convenient time
  • Stopping a laxative after using one frequently
  • Pregnancy
  • Using certain medications, particularly iron, some chemotherapy drugs, and those used for treating pain (opiates), nausea, and depression

Less commonly, an underlying health problem is the cause of your constipation. Some examples include:

  • A neurological problem (for example, multiple sclerosis or Parkinson's disease)
  • A psychiatric problem (for example, anorexia nervosa)
  • A metabolic disorder (for example, diabetes mellitus, an underactive thyroid, or a high calcium level)
  • Something blocking the gastrointestinal tract (for example, colon cancer)

Constipation As a Symptom of Colon Cancer

When stool enters the colon, it's a thick liquid that can flow around partial blockages or through narrow areas. As it progresses through the colon and more water is removed, it becomes thicker. This inhibits its ability to get around blockages and narrow areas. This is why a tumor in the middle to lower portions of the colon, or in the rectum, can make it difficult for stool to pass by, leading to constipation.

Other Symptoms of Colon Cancer

Of course, besides constipation, there are many other potential symptoms of colon cancer.

In fact, on the other end of the spectrum, diarrhea could be a symptom of colon cancer.

This is why if you notice any changes in your bowel habits, talk to your doctor. In many cases, you will find out that you do not have colon cancer and that something less serious is causing your constipation. But it's better to err on the side of caution and get it checked out.

On that note, besides a change in your bowel habits, other symptoms of colon cancer may include:

  • Bleeding from your rectum with bright red blood
  • Blood in your stool (note that blood can make your stool look black)
  • Belly pain or cramping or rectal pain 
  • Unusual fatigue
  • Weight loss that is unintentional

Finding the Cause of Your Symptoms

When you see your doctor for constipation, he will ask you questions regarding your medications, diet, and family history. He may also perform a rectal examination, as well as blood tests, to check for anemia, thyroid disease, or a high calcium level.

If there is no obvious cause for your constipation or if your doctor is suspicious for cancer, you will be referred to a doctor who specializes in diseases of the gastrointestinal tract (called a gastroenterologist).

A gastroenterologist can perform a colonoscopy to help determine the cause of your symptoms. Sometimes, more sophisticated tests are needed to ultimately find the cause of your constipation. 

A Word From Verywell

The big picture here is that constipation is a very common problem, and for the majority, constipation is not due to colon cancer. Even so, be sure to get to the bottom of your constipation—you deserve to feel well, and your bowel health plays a big role in your everyday quality of life.

Plus, in the event you are diagnosed with colon cancer, the sooner you get a diagnosis the better. In fact, according to the American Cancer Society, if diagnosed in the earliest stages, survival rates for colon cancer are around 90 percent. If the cancer is more advanced and has spread beyond the colon, survival rates drop dramatically.


American Cancer Society. (2017). Can Coloectal Piolyps and Cancer Be Found Early?: Why is it important to find colorectal cancer early?

Mearin F et al. Bowel Disorders. Gastroenterology. 2016 Feb 18.

Namirah J, Zone-En L, Olden KW. Diagnostic approach to chronic constipation in adults. Am Fam Physician. 2011 Aug 1;84(3):299-306.