You cannot see your adenoids. If needed, a doctor can look at the adenoids either by using a light and a small mirror held at the back of the mouth, or by using a small flexible telescope. Occasionally, an X-ray is done to determine the size of the adenoids. Like tonsils, adenoids help to defend the body from infection. They trap bacteria and viruses which you breathe in through your nose. They contain cells and antibodies of the immune system to help prevent throat and lung infections.