Meet the best surgeon for colorectal surgery singapore at Alpine Surgical. The symptoms of colorectal cancer are based on the current stage it occurs. During the early stages, the symptoms include:Blood in the stool (bright or very dark red) , Abdominal pain , Abdominal cramps,Haemorrhage in the rectum , Change in bowel movement shape, Constipation , Excessive gas, Diarrhoea etc.