Toilet trouble in dogs

My nine-year-old German shepherd began leaking puddles where she was sleeping, especially overnight.

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Otherwise, when out and about she urinates normally. My vet ran some tests and has diagnosed a weakness of the sphincter muscle controlling the bladder. She has started treatment but is it a common problem and what causes it?

Urinary incontinence in female dogs is common, especially in middle-aged to older female spayed dogs. The diagnosis that your vet has made has a slightly complicated name - urethral sphincter mechanism incompetence (USMI). This simply means that the sphincter muscle surrounding the neck of the bladder weakens, and allows urine to leak out, especially when the dog is resting or asleep.

The history you gave your vet does point to USMI, urinating normally during the day, but leaking at night.