As a veterinarian, I hear fairly often that a spayed female dog is leaking urine, usually in her sleep. This can be a sign of a urinary tract infection or another health condition, so your first step should be to rule those out. But it’s likely this is what’s known as spay or estrogen-responsive urinary incontinence.
This is a form of urinary leaking caused by a lack of estrogen, which controls the dog’s ability to hold in urine when the bladder is full. It tends to be worse when the dog is asleep, and you will find wet spots where your dog was resting.
Why do spayed females have a tendency to leak urine? Because a lack of estrogen weakends the urinary sphincter.
Fortunately, spay incontinence is usually easy to treat. Your veterinarian will likely prescribe either the drug phenylpropanolamine (PPA, brand name Proin), which tightens the sphincter muscle, or horomone replacement therapy with diethylstilbestrol (DES) or estriol (brand name Incurin), a natural estrogen hormone.