According to the University of Maryland Medical Center, colon cancer is the second most commonly diagnosed cancer in American men and women. Tumours in the colon (large intestine) grow slowly and have few symptoms, so they are difficult to detect until they have spread or grown to a noticeable size. End-stage colon cancer has three main symptoms.
Fatigue and weakness
Most colon cancers bleed, according to the Merck Manual of Medical Information. Depending on the location of the tumours, however, the blood may not be noticeable, but hidden bleeding ("occult" bleeding) will still affect the body. Weakness from blood loss is a primary symptom of occult bleeding, as is general fatigue and lack of ability to exercise. The University of Maryland reports that other symptoms associated with blood loss, such as anaemia, shortness of breath or a racing heartbeat, can occur as well.
Constipation, diarrhoea and pain can indicate the presence of colon cancer, according to the University of Maryland Medical Center. How and when symptoms occur depends on the tumour's location. The Merck Manual states that a tumour on the left side of the colon will cause pain and blockage earlier because the left side has a smaller diameter and stool is semisolid in this part of the colon. Right-side tumours can grow undetected until they are large enough for a doctor to feel through the abdominal wall, mostly because the right side of the colon has a larger diameter and stool is liquid when it travels through the right side.
End-stage colon cancers will bleed noticeably, causing blood-streaked stool, according to the Merck Manual. Colon cancers that occur in the last 6 inches of the colon will cause the rectum to bleed during a bowel movement.