Even funnier in the UK is what we do when we get to the loo (slang versions inc).

Slash (male) usually said amongst men
Splash my boots (uncareful male) the same or close family
Spend a penny (ladies) when out in company
Have a tinkle (ladies or children)
Make room for the beer (either)
or
Why didn't you say you wanted to go before we left (to children)
Nature calls (mixed company)

The US powdering the nose really does sound better than that unless of course there are any euphemisms for the function of relieving the bladder?

I won't ask about the other!