Both haemorrhoids and cancer can cause blood in the stools. Haemorrhoids may also lead to itching in the anal area and/or a lump being felt outside the anus. In colorectal cancer, there is usually no anal itching. Without a colonoscopy, it is not always possible to tell the difference between haemorrhoids and colorectal cancer. If you experience persistent blood in your stools, do consult your doctor for a proper diagnosis as soon as possible.