We used this to good effect with our chronic UTI problem dog:
[ame="http://www.amazon.com/Nutramax-Count-Cranandin-Pet-Supplement/dp/B004H22KZK/ref=sr_1_9?ie=UTF8&qid=1412445700&sr=8-9&keywords=cranberry+for+dogs"]Amazon.com: Nutramax 21 Count Cranandin Pet Supplement: Pet Supplies[/ame]
It worked better than the 'human' supplement because it had dosage recommendations for a 10 lb lapdog (our daughter's Pekingese).
My wife says, "Antibiotics to clear it up, and Cranandin to prevent recurrence." Princess struggled with UTIs for a couple of years before Jenn figured this out.