A diagnosis of colorectal cancer indicates that cancer has begun in the rectum or colon. Cancer refers to the out of control growth of cells within the body. Also referred to as rectal cancer or colon cancer, depending on their places of origin, these cancers are generally grouped together because of their many commonalities.

Changes in Bowel Habits

The symptoms of colorectal cancer may not appear at once; if the cancer does cause symptoms, they may include a wide range of effects. One is a change in the habits of the bowel, such as constipation, diarrhea, or a narrowing in the size of the stool. This is potentially a symptom if it lasts longer than several days.

Abdominal Changes

Cramps in the abdomen or belly may indicate a problem such as colorectal cancer. General pain in that area may also be a warning sign. Another is the sensation of needing to move the bowels; this sensation is not relieved by actually having a bowel movement. This feeling is known as tenesmus.

Overall Body Changes

Weakness and fatigue can be a symptom of colorectal cancer. This does not include general tiredness from lack of sleep or weakness after a thorough workout, but fatigue and weakness with no apparent cause. Unintended weight loss is also systematic of this kind of cancer. It is important to keep a baseline knowledge of the general weight to know if changes occur and consult a doctor if they are drastic and without a cause that can be pointed to. Jaundice and unexplained losses of appetite may also be a sign of colorectal cancers.

Blood as a Symptom

Colorectal cancers are often known to bleed into the digestive tract. They can cause rectal bleeding; this is a sign if the blood is bright red. They can also cause blood in the stool, which can make the resulting stool appear darker than usual.


Because of colorectal cancers causing bleeding, one of the first signs of colorectal cancer may be a blood test that reveals a low count of red blood cells. This condition is known as anemia. The blood loss builds up over time and anemia is the result. The cause of fatigue may be cancer-related anemia.