swollen pale kidneys

I have recently culled a number of cockerals and have noticed that they all have swollen and pale kidneys. All of the birds seemed in good health so not sure if I have a problem or not. Been looking on the web but can only really find long scientific articles that don't tell me what the problem could be any ideas would be greatly appreciated.

Not trying to be funny, but are you sure you have identified the kidneys and not the testes?

Some of the rarer forms of Mareks disease can produce swollen pale kidneys without all of the others symptoms. I would definately recommend a chat with the vet in case it is this form of the disease.