What Are the Symptoms of Colon Cancer?

Colon cancer symptoms
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Even with the adoption of colon cancer screening, many people are diagnosed only after the cancer is in the later, more difficult-to-treat stages of the disease. As the third leading cause of cancer-related deaths in both men and women in the United States, it's clear we have a way to go. Having an understanding of the possible signs and symptoms of colon cancer can help people seek medical attention as early as possible, when the cancer is in the most treatable stages.

What are the symptoms of colon cancer that you should watch for, and why do these occur?

Anatomy and Function of the Colon

In order to understand what colon cancer symptoms might feel like, it helps to briefly review both the anatomy and function of the colon. Pain in the location of your body near your colon might alert you to a problem, as may symptoms that suggest your bowel is not functioning as it should.

The colon makes up most of the large intestine, approximately 6 feet in length. The last 6 inches or so of the large intestine are the rectum and the anal canal. Many people think of the small intestine as being "on top" and the large intestine as "being down below," but there is actually overlap, and much of the large intestine lies above the small intestine. The colon is shaped like a lean-to, with the ascending colon traveling up the right side of your abdomen, the transverse colon traveling horizontally across your upper abdomen, and the descending colon traveling from just under your ribs on the left, down to the rectum and anus.

The colon plays an important role in the digestive system, and we've learned that its role is more than just dehydrating waste so that it can be passed out of the body. In addition to playing a role in regulating fluids, the colon absorbs nutrients and minerals. We are learning that "gut bacteria" do not just contribute to the smell of stool, but can play a role in many medical conditions and even mood.

Symptoms of Colon Cancer

Colon cancer can have many symptoms. However, in the early stages, people with colon cancer often have no symptoms at all. This is why regular screening beginning at 50 (and earlier for those with risk factors) is an important investment in your healthy future.

Colon cancer symptoms come in two general varieties:

  • Local: Local symptoms are those that occur due to the location of a tumor in the colon.
  • Systemic: Systemic symptoms are often seen when a colon cancer is advanced, and especially if it has spread beyond the colon. These symptoms may be related to the metabolism of the tumor, or due to the spread (metastasis) of the tumor to other organs.

Local Colon Cancer Symptoms

Local colon cancer symptoms affect your bathroom habits and the colon itself. Some of the more common local symptoms of colon cancer include:

  • Changes in your bowel habits. Any significant change in your bowel habits should prompt a discussion with your doctor. This may include bowel movements that are either more or less frequent than normal. Different people have different bowels habits. The important thing to be alert for is any change in your normal pattern of bowel movements.
  • Constipation. While it's not the most common cause, colon cancer is one of the conditions that can lead to constipation. If you are having difficulty having a bowel movement, or are straining, talk to your doctor.
  • Diarrhea. Loose and watery stools can also be a symptom of colon cancer, though again, there are more likely causes. Unless you have an explanation for your diarrhea, and it resolves in a reasonable amount of time, talk to your doctor.
  • Intermittent (alternating) constipation and diarrhea. It's not uncommon for colon cancer to result in symptoms of alternating diarrhea and constipation. This may occur when there is a partial obstruction (due to tumor) in the bowel. Constipation may occur due to difficulty in stool passing the obstruction, followed by diarrhea when backed up contents are then passed.
  • Bright red or dark red blood in your stools. Bleeding in the colon due to colon cancer often results in bright red or dark red blood in the stools. When a colon cancer occurs higher up in the colon, such as in the right colon, blood may instead appear as black or "tarry" appearing stools. 
  • Stools that are thinner than normal. "Pencil stools" may be a symptom of colon cancer, and are usually related to an obstruction caused by a tumor, which leads to thin stools.
  • A feeling of being unable to completely empty your bowels. If you feel like you still need to go to the bathroom even though you've had a bowel movement, you should talk to your doctor.
  • Abdominal (midsection) discomfort, bloating, frequent gas pains, or cramps. Abdominal pain or cramping may occur for several reasons in those who have colon cancer. These symptoms may be intermittent at first and dismissed as dietary in nature.
  • A general sense that something is wrong. It's not uncommon for people to have a sense that something is amiss in their body, even if they don't have specific symptoms to back up that feeling. Trust your intuition. If you are concerned that something is wrong, it could be. Make an appointment and talk to your doctor.

If you experience any of these for two or more weeks (or if you have blood in your stool even just once), call your doctor right away to discuss your concerns and arrange for tests to get to the bottom of your symptoms.

Systemic Colon Cancer Symptoms

Systemic colon cancer symptoms are those that affect your whole body, such as weight loss, and include:

  • Unintentional weight loss. If you lose weight without trying, you may, at first, be pleased. But unintentional weight loss is an important symptom that shouldn't be ignored. It's described as losing 5 percent or more of body weight over a 6 to 12 month period. For example, if a 150-pound woman lost 7.5 pounds for no apparent reason, she should contact her physician. Colon cancer is only one of several serious conditions that might first declare themselves with unexpected weight loss.
  • Loss of appetite. Loss of appetite is an important symptom. It most often occurs with advanced cancers, but has been noted in some people with early colon cancer as well. Talk to your doctor if food has lost its role in your life.
  • Unexplained fatigue. Extreme tiredness is a nonspecific symptom, but is very common in people with more advanced cancers. Cancer fatigue differs from "ordinary" fatigue in that it's not usually relieved by rest and isn't counteracted by a good cup of coffee.
  • Nausea or vomiting. Nausea and vomiting may occur at any stage of colon cancer, but is more common with advanced disease.
  • Anemia (low red blood cell count). Anemia may occur as the first sign of colon cancer, due to microscopic bleeding from a tumor. It's also common with more advanced cancers. A low red blood cell count is also associated with a poorer prognosis.
  • Jaundice. Jaundice, a condition in which the skin and whites of the eyes take on a yellowish appearance, may be a sign of colon cancer. Jaundice may occur when colon cancer spreads to the liver, a common site of metastasis for colon cancers. It may also occur due to pressure from a colon cancer on important structures related to the liver.

If you experience any of these for any length of time, even a few days, call your doctor right away to discuss your concerns and arrange for tests to get to the bottom of your symptoms.

Making an Appointment to Discuss Your Symptoms

Call your doctor so she can set up an appointment to see you. During the appointment, your doctor will take a medical history, perform a physical exam, collect blood samples for testing, and schedule you for follow-up tests if needed.

Many people are afraid of colon cancer screening. They worry that it will hurt and that it is embarrassing. Your doctor and nurse have performed hundreds and in some cases even thousands of these procedures. There is nothing to be embarrassed about and remember: Even your doctor and nurse undergo these same tests to take care of their own health.

Preparing for Colon Cancer Tests

If you are worried about preparing for your colon cancer tests, ask your doctor about how best to get ready for any procedures. There are different medications for clearing your colon of stool to ensure a good screening. There is no reason to suffer in silence.

Evaluating Your Risk of Colon Cancer

It can be helpful to determine if you have an increased risk of developing colon cancer, as you may wish to undergo screening earlier than guidelines recommend. That said, anyone can develop colon cancer. If you have a colon, you can develop colon cancer. It's also noteworthy that, even though screening is recommended at age 50, people without any risk factors can and do sometimes get colon cancer before the age of 50.

A Word From Verywell on Colon Cancer Symptoms

While many people have heard that having blood in their stools may be a sign of colon cancer, just about any change in your bowel habits is worth evaluating. Everyone is different, and what is normal for someone else may not be normal for you. Make sure to talk to your doctor if you have any changes. Of note, is that symptoms such as alternating between constipation and diarrhea, and even a sense that you aren't completely emptying your bowels, should be investigated.

In addition to local symptoms, systemic symptoms such as fatigue, unintentional weight loss, a loss of appetite, or anemia are also important symptoms of colon cancer.

Fortunately, we now have screening tests such as colonoscopy which have been found to reduce the risk of dying from colon cancer. Colon cancer screening is unique in that it may not only lead to the early detection of cancer (and colon cancer is most curable in the early stages), but may prevent colon cancer in the first place, if a precancerous polyp is found and removed.

It's important to be your own advocate for your health care. If you aren't getting answers, keep asking questions. If you still aren't getting answers, consider getting a second opinion. Being a squeaky wheel when it comes to your health care will not only help you get the attention you need, but may affect your long-term health, and even survival, as well.

Sources:

Del Giudice, M., Vella, E., Hey, A. et al. Systematic Review of Clinical Features of Suspected Colorectal Cancer in Primary Care. Canadian Family Physician. 2014. 60(8):e405-15.

Kasper, Dennis L.., Anthony S. Fauci, and Stephen L.. Hauser. Harrison's Principles of Internal Medicine. New York: Mc Graw Hill education, 2015. Print.

National Cancer Institute. Colon Cancer Treatment (PDQ)—Health Professional Version. Updated 02/18/28. https://www.cancer.gov/types/colorectal/hp/colon-treatment-pdq