General: The first thing that comes to mind is 'cute'. Toddlers running around in the buff (or no) are usually quite funny.
Composition: Placement of your subject is good with him looking into the rest of the frame. The fence is a bit distracting though. It might of worked better if the fence were out of focus (less DOF).
Exposure: The exposure seems to be a little too much, probably 1/3 or 1/2 a stop. The child's shoulder and hair seem just slightly over exposed.
Impact: I believe you were attempting to get impact with the portrayed activity. Unfortunately it doesn't work here though it's a great family/'show to the first date' picture.
I very much don't like your subject here. I really have no interest in seeing a kid peeing. The photo itself is pretty straightforward and while it isn't cluttered and the technical aspects seem fine, it doesn't really have much to offer besides the subject, which as I said is completely unappealing to me.
funny, but although he is nude, I wouldn't call it a nude. In nude photography, you'd assume that the nudity is there for a reason, to invoke some kind of response or connotation. This does none of the above (not for me, anyway)
I assume it's an edit...maybe not. good enough to fool most if it is. Other than that the pic doesn't do much for me. A fill flash would help some of the shadows (the shadows don't add much to the composition if they were intentional), and I might incread the depth to blur the background a bit.