Is there a technical term for this particular physiological reaction? (please read details)

I have wondered about this for a long time. Even Cecil at the Straight Dope refused to check into it, due to the ick factor, I suppose. Why is it that you sometimes get a body shiver after you go pee, even though room temperature is not a factor? This is known in popular parlance as ‘the piss shiver’. Is there any biological reason for it, or is it simply something that has no real evolutionary and/or biological meaning or purpose?