I have one like that
One year we took her on holiday to the Lake District & she didn't wee for the whole of the first day.
On the second day, by which time I was beginning to worry that she'd burst, she finally let go of an absolute flood as we were walking across a shallow stream near the Roman Fort at the top of Hardknott Pass.
Think the sound of trickling water & wet feet finally got to her!
xx
Meggie