My Uni flatmate pissed on the kitchen floor

I went into the kitchen at 1 in the morning, the light works by a sensor so it takes a bit to turn on. I walked in like I usually do just to slip into a big puddle of what I thought was water. I tried to get up just to put my hands in it and slip a bit more. When I got up there was the unmistakable smell of piss from the puddle and on myself. My room mate never rarely leaves his room so how do I bring this up to him? I am traumatised for life.

What do I do?