Colorectal cancer may occur without any symptoms therefore it is very important to have regular examinations called colorectal screenings, to detect early problems. One of the earliest signs of colon cancer is bleeding, which may be painless. Sometimes the blood is found only during chemical testing of the stool.

When tumors have grown larger, other symptoms may develop. These symptoms may include

Blood on or in the stool
Constipation
Bowel obstruction, causing nausea, vomiting and abdominal distention
Diarrhea
Anemia
Stools that are narrower than usual
Loss of appetite
General abdominal discomfort like stomach or gas pain
Weight loss with no known reason
Fatigue
Constant tiredness
Pelvic pain

For colorectal cancer patients, early diagnosis and treatment can be a life-saver. So if any of these symptoms are found, better consult a physician to ensure proper diagnosis and treatment.