Question: is constipation or diarrhea a sign of colon cancer?
Answer: The commonest symptom of colorectal cancer is a change of bowel habits. There may be increasing constipation, or perhaps alternating bouts of constipation and diarrhoea. There may be blood or mucus in the stools. A feeling that you haven't completely emptied your bowels is quite common if the tumour is in the rectum.