Excuse me for a moment please
This leaves both purpose and destination unstated, but by making it clear that the absence will be very temporary, does not cause anyone to think that it is a total departure. This will usually be understood sufficiently in context.
There are of course, many euphemisms, some gender specific, some not, some considered more polite than others.
- I need the small room.
- I need to powder my nose. (a bit old-fashioned.)
- I need the lav. (out of date?)
- You don't buy beer, you rent it. (perhaps too graphic, but less so than "piss").
- I need the John.
and many many others
Devon's answer reminded me of
When Nature is calling, plain speaking is out,
When ladies, God bless 'em, are milling about,
You make water, wee-wee, or empty the glass;
You can powder your nose; "Excuse me" may pass;
Shake the dew off the lily; see a man 'bout a dog;
Or when everyone's soused, it's condensing the fog,
But be pleased to remember if you would know bliss -
That only in Shakespeare do characters piss!
one stanza from this which i first read in The Lure of the Limerick