Your urine flow slows down days after a ride. The number of times you have to pee. The quantity you have to pee. Or if it really haw strong the flow of urine is coming from you?

For the first two, it's probably just that you drink more on the day you ride. Days later you probably are just not drinking as much.

As for the latter, it probably has more to do with you and nothing to do with the saddle. Perhaps you should talk with your doctor about it.

Doctors have said I had a enlarged prostate for many of the annual medical checks I did during my middle ages. Never did I equate any of it to cycling or the saddle.