The Colon’s Function

The colon, together with the rectum is known as the large intestine. Its main function is to store feces and absorb water. Essentially the last part of the digestive system, whatever nutrients that were not absorbed by the small intestines will pass into the colon, and eventually out of the body during bowel movements.


Colon cancer originates from the inner lining or mucosa of the colon. As the colon’s lining is continuously growing and shedding, the lining or mucosa is constantly going through cell replication. And with each replication comes a chance of mutation.

Although most mutations are quickly recognized as mistakes and removed by the body, some escape the body’s defense mechanism and continue to multiply, eventually turning cancerous.

Most cases of colon cancer follow the adenoma-carcinoma sequence, which means that the abnormal growth is initially benign (adenoma) before turning cancerous (carcinoma). In most cases, colon cancer begins as a benign polyp, which, if not detected and removed, may turn cancerous eventually.


Unfortunately, early stages of colon cancer do not usually display any symptoms at all, even if the polyp was large in size.

Symptoms also depend greatly on the location of the cancer and its distance from the end of the colon: tumors on the right side of the colon usually do not cause much symptoms because semi-solid stools (that just entered from the small intestines) can flow past most tumors with little problem. The cancerous tumor may bleed, causing blood to be mixed with the stool. However, this would be invisible to the naked eye.

On the other hand, stools on the left side of the colon are more solid (having travelled through the colon and having more of the water absorbed), thus the effects of the cancer on the stools become more obvious. These effects include blood-coated stools, constipation and narrower stools.

A possible complication of tumors is intestinal obstruction, which occurs when the passageway is entirely blocked, such that stools are not able to pass through. This results in abdominal pain, distension and eventually, vomiting.

All these symptoms serve to further highlight the importance of regular colon cancer screenings so that any abnormal growths (including symptomless ones) can be caught early and removed.


  • Age: Most cases of colon cancer occur in patients over the age of 50
  • Family History: Those with a close family member with colon cancer are at greater risk
    • First-degree relative (parents, children, siblings) -> 6% risk
    • If the said relative was below 50 when diagnosed -> 10% risk
    • Two first-degree relatives (e.g. father and brother) -> 17% risk
    • Three first-degree relatives -> 50% risk
  • Personal History of Colon Cancer & Polyps: Either of this will result in an increased risk of getting cancer or a recurrence. The earlier the age of the first cancer and the greater the number of polyps, the higher the risk
  • Personal History of Inflammatory Bowel Disease (IBD): IBD causes chronic inflammation of the intestines and increases the risk of colon cancer