Colon Cancer Symptoms

June 27, 2021

What are the symptoms colon cancer?

Constipation, blood in the stool, anemia and weight loss

by Jamal Ross

Before we begin our discussion on the symptoms of colon cancer, it is important to realize that it is our goal to detect colon cancer before symptoms develop. When we begin to have symptoms of colon cancer, many times it is too late and the cancer has spread to other parts of the body. This is why it is extremely important that you have a colonoscopy between the ages of 40 to 50. Depending on your family history and risk, you may even require a colonoscopy at a younger age. For more information about the right time for you to get a colonoscopy, read our blog: “When Should I Get a Colonoscopy?” With that being said, it is important to know the most common symptoms of colon as a means to uncover this diagnosis in those who have not had a colonoscopy. Colon cancer symptoms include changes in the way someone passes their stool, abdominal pain, anemia or weight loss. At other times one may have no symptoms at all. Let’s find out more about the symptoms of colon cancer.

 One of the most common symptoms of colon cancer is a change in the way someone would normally have a bowel movement. This is called a change in bowel habits. It is thought that around 74% of those with colon cancer will have a change in their bowel habits (1) These changes can vary greatly and include diarrhea, constipation or “pencil-like” thin stools. When a mass has blocked the tunnel of the colon, one may not be able to have a bowel movement. This leads to constipation, or the inability to pass stool. This constipation may continue despite eating normally and taking a laxative. At other times, when stool cannot get around a blockage, there may be leakage around it, leading to diarrhea.  Finally, when only a small part of stool is able to pass a blockage, the result may be a decrease in the caliber or bulkiness of stool. In this case, stool may be thin and “pencil-like.” These changes in bowel habits tend to be more common if the cancer is on the left side of the colon.

Another common symptom of colon cancer involves having blood in your stool. Passing blood in our stool can be seen in about 37% of the cases of colon cancer (2) This blood may be bright red or marron in color. At other times, it may be black in color. There could be small or large amounts of blood. Having pain in the abdomen is another symptom of colon cancer, but usually there are other symptoms such as a change in bowel habits or blood in the stool that is experienced along with abdominal pain. Abdominal alone as a symptom of colon cancer is only present in about 3% to 4% of the cases. (1) As with many cancers, weight loss can also be seen with colon cancer.

Anemia, or a low number of red blood cells, is also another common symptom of colon cancer. About 23% of the cases of colon cancer involves anemia. (2) The red cells in our body help transport oxygen. Therefore, with anemia, one may feel tired and become short of breath easily. At other times our body compensates and we may have little to no symptoms and the anemia discovered by accident on basic blood tests obtained by the doctor. The anemia seen with colon cancer is caused by a mass in the colon that bleeds slowly. As we pass blood in our stool slowly over time, we also lose the iron within these red cells as well. This type of anemia is called iron deficiency anemia. While there are many causes of anemia, such as menstrual blood loss and low iron in our diet, anemia with low iron in the elderly should be taken very seriously and colon cancer should strongly be considered. In this case, speak with you doctor immediately

In all, the symptoms of colon include changes in bowel habits, passing blood in the stool, abdominal pain, anemia or weight loss. The changes in our bowel habits include experiencing bowel blockage, constipation, passing “pencil-like” stools or even having diarrhea. At other times, one may experience tiredness from anemia caused by a mass in the colon that bleeds very slowly. Of note, there are many causes of anemia including menstrual blood losses and low amounts of iron in our diet. Yet, anemia due to low amounts of iron in the elderly or middle-aged who have not had a colonoscopy should be taken very seriously. Furthermore, bleeding from colon cancer can be so small that it cannot be seen with by naked eye. Also, when blood is seen in the stool, there can be other explanations, such as a bleeding hemorrhoid. Yet, any blood witnessed in the stool should also be taken seriously; and again, you should see you doctor immediately. Here is the bottom line: you should have your colonoscopy at the appropriate age, based on you family history and risk, when you have no symptoms. If you wait for symptoms to develop, colon cancer may have already left the station and is on its way to stage IV disease. Let’s not wait for things to get out of control. Instead, use the wisdom of God to become obedient to the advice of our medical professionals and stop a deadly disease that is preventable.

1. Thompson MR, O’Leary DP, Flashman K, Asiimwe A, Ellis BG, Senapati A. Clinical assessment to determine the risk of bowel cancer using Symptoms, Age, Mass and Iron deficiency anaemia (SAMI). Br J Surg. 2017 Sep;104(10):1393-1404.
2. Moreno CC, Mittal PK, Sullivan PS, Rutherford R, Staley CA, Cardona K, Hawk NN, Dixon WT, Kitajima HD, Kang J, Small WC, Oshinski J, Votaw JR. Colorectal Cancer Initial Diagnosis: Screening Colonoscopy, Diagnostic Colonoscopy, or Emergent Surgery, and Tumor Stage and Size at Initial Presentation. Clin Colorectal Cancer. 2016 Mar;15(1):67-73.

Jamal Ross

Dr. Jamal Ross is an internist and pediatrician who possesses a passion for prayer and preventative medicine. He has worked in the fields of primary care and hospital medicine.

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