What Causes Brown Spots On My Face When Exposed To Sun?

I am a 25 year old male who is about 5' 5" and weighs 135. I was in a bad car accident several years ago and had to have my spleen removed. In the last several years I've started getting brown spots on my face, especially when I've been out in the sun. I was wondering if these are a sign of kidney or liver diesease or if they're just a result of too much sun exposure.