These tests find out the position of the cancer, its size and whether it has spread. This is called the stage. Knowing this helps your doctor decide which treatment you need.
You might have a CT scan to find out the size of the cancer in your anus and whether it has spread to other parts of your body.
MRI stands for magnetic resonance imaging. It uses magnetism and radio waves to create cross sectional pictures of the body.
A PET-CT scan combines a CT scan and a PET scan into one. It can show where your anal cancer is and whether it has spread.
Ultrasound scans use high frequency sound waves to create a picture of a part of the body. They can show up changes, including abnormal growths.
Your doctor might use a thin needle to take a sample of cells from the lymph nodes at the top of your legs. This is called a fine needle aspiration.