is it safe for uritheral sounds?

Answer 1

I'm okay with all kinds of kinks, but of the three people I've known who were into urethral sounding, two managed to hurt themselves bad enough to seek medical attention.

One gave himself a bad bladder infection, and the other injured the urethra.

It's not something I'd consider playing.

Answer 2

It's spelled urethral. 

And no, not ideally.