Bowel cancer, also known as colorectal cancer, is the name for any cancer of your large bowel and rectum (back passage). Very rarely, cancers can occur in your small bowel.
Your large bowel (also called your colon) is the last section of your digestive system. Food passes through your small bowel (the longer, thinner part of your bowel) where nutrients are absorbed. Food waste then travels through your large bowel, where it becomes more solid faeces.
Your large bowel has three sections: the ascending; transverse; and descending colon. Your rectum, at the end of your large bowel, is where faeces collects before passing through your anus as a bowel movement.
Usually, large bowel cancers develop from small, non-cancerous (benign) growths of tissue called polyps that can extend from the lining of your bowel wall. Sometimes polyps can become cancerous (malignant) over time. If the cancer isn't treated, it can grow through the wall of your bowel and spread to other parts of your body.