Possible signs of cancer of the colon and/or rectum include a change in bowel habits or blood in the stool. These and other symptoms may be caused by colon and/or rectum cancer. Other conditions may cause the same symptoms. A doctor should be consulted if any of the following problems occur:

• A change in bowel habits
• Blood (either bright red or very dark) in the stool
• Diarrhea, constipation, or feeling that the bowel does not empty completely
• Stools that are narrower than usual
• Frequent gas pains, bloating, fullness, or cramps
• Weight loss for no known reason
• Feeling very tired
• Vomiting