
I would suspect it is stress incontinence, but the bladder happened to be full, ti is most likely due to the lack of hormones making the muscles weak.
A trip to the Vet is needed anyway where he can check for an infection.
There are two drugs used for spay incontinence. Both of which may cause attractiveness to males as a side effect, one more than the other. Sometimes they don't work, but I have known several Dobe bitches on treatment who did well (seems to be common for spay incontinence in that breed).