How Does Colon Cancer Affect a Person's Body?

Last Editorial Review: 8/24/2017

Ask the experts

My doctor told me I may have colon cancer after my colonoscopy, but I don't have any symptoms yet. What symptoms and signs can I expect if my upcoming tests prove positive for colon cancer?

Doctor's response

Symptoms of colorectal cancer are numerous and nonspecific. They include:

Other conditions such as irritable bowel syndrome (spastic colon), ulcerative colitis, Crohn's disease, diverticulosis, and peptic ulcer disease can have symptoms that mimic colorectal cancer.

Colorectal cancer can be present for several years before symptoms develop. Symptoms vary according to where in the large intestine the tumor is located. The right colon is wider and more flexible. It can even be called relatively spacious as compared to the rest of the colon. Cancers of the right colon can grow to large sizes before they cause any abdominal symptoms. Typically, right-sided cancers cause iron deficiency anemia due to the slow loss of blood over a long period of time. Iron deficiency anemia causes:

  • fatigue,
  • weakness, and
  • shortness of breath.

The left colon is narrower than the right colon. Therefore, cancers of the left colon are more likely to cause partial or complete bowel obstruction. Cancers causing partial bowel obstruction can cause symptoms of:

Bright red blood in the stool may also indicate a growth near the end of the left colon or rectum.

"Clinical presentation, diagnosis, and staging of colorectal cancer"