Who is your audience?
I know what you mean. I'm not sure how natural it is. But then, we don't tend to talk about these things often, so it's hard to say what might sound natural. We tend to not like words that relate to bodily functions, like "urine."
"Waiting too long to void your bladder" is certainly clear.
If you're talking in a non-medical setting, with an informal tone, "waiting too long to pee" would even work.
Student or Learner