I have kidney cancer and my main symptoms were back pain and exhaustion.
Many people get blood in their urine, but that didn't happen to me.
Personally,I think it would be extremely rare for you to have kidney cancer.
It's mainly thought to be an old man's disease.
Having said that, people of both sexes get kidney cancer from middle age - it's just most common in men over 60.
There is a special type of kidney tumour that children can get, but at 13 you are a bit old for childhood cancer.
I guess the best thing you can do is have all the tests but relax a little knowing that it's highly unlikely to be cancerous at your age.
Whatever it is, it's a good thing they found it before it gave you any real complications.
Good luck xx