Leakers "Hormone Responsive Incontinence":

Sometimes a female dog will leak urine.
There are a LOT of possible causes but there's a couple things:
One cohort of female-dogs is usually between 1 and 4 years old.
However, the problem can re-appear when they're really old because nerves to the bladder start to weaken. So you can see this in the 10 year olds, too.
They're almost always spayed.
They're almost-always fully housebroken - so the owners are understandably mystified.
And it appears to be when they're RESTING - they don't hold 'the posture'.

So we think of them as "leakers" and what THAT is, a weak bladder. (Actually a weak urethra) which can sometimes be a lifelong thing, or sometimes 'go away' after a couple months.

We always check for a Urinary infection.
If that's negative, or we're unsure, we can start PROIN - (phenylpropanolamine). After a week or two on that, twice a day, most folks see the leaking STOP and then they switch to ONCE a day dosing.
After a couple months you try OFF that medicine to see if it's *actually* a lifelong requirement.

What causes it? Not sure of the neurological or hormonal cascade.

Doc Johnson