In some situations it might be considered vulgar or lower style to say "I have to go to the toilet". In English there are many ways around this: you can call the toilet something finer (bathroom, restroom, men's room…) or you can substitute another activity (like going to powder one's nose).
How do I excuse myself in Latin in good style if I have such private business to attend to? I suppose I could just translate any of the common euphemisms in other languages, but I thought there might be something more idiomatic in Latin.