In many cases, colorectal cancer may not have any symptoms. It is often found by using a screening test. But you should tell your doctor if you have any of the following symptoms:
Bleeding from your rectum or blood in your stool.
Feeling that your bowel does not empty completely.
Cramping, frequent gas, bloating, a feeling of fullness, or vomiting.
Weight loss when you are not trying to lose weight.
Having these symptoms does not mean that you definitely have cancer. Many of these symptoms can be caused by other problems. You may need tests to know for sure what is causing your symptoms.