[anonymous]

Also, if the dog is overweight, get the extra weight off, increase walks/exercise/activity.
Work closely with your vet, when the dog has been stable 6 months to 1 year then you can talk about diet changes.
“Dogs that get urinary tract infections and bladder stones tend to have a genetic predisposition, combine that with not enough water intake, not enough opportunities to urinate and you have a problem”.
“Whatever you decide to feed, add water to the kibble or canned food, even presoak and add water. Take out to urinate at least every 4 hours (every 2 hours is ideal) stagnant conditions in the bladder are conducive to bladder stone formation”.
“Always have fresh water available for the dog 24/7”.
“Supplements are crap, don’t waste your money unless your vet recommends something specific for your dog”.
Ps: You think the prescription food is expensive. Try emergency surgery for a blocked urethra.
Been there, done that.
Per the search engine: /forums/search/urinary+tract+infections/
Regarding cranberry: http://skeptvet.com/Blog/?s=cranberry
Also there are prescription meds for stubborn cases, talk to your vet.
Was an ultrasound done? Dogs can have more than one type of stone, such as calcium oxalate and struvite…that was the case with my dog that had reoccurring UTIs.
This is not veterinary advice; consult your veterinarian.

PS: Note recent question on struvite in comments: http://skeptvet.com/Blog/2016/09/science-based-veterinary-nutrition-success-stories/comment-page-1/#comment-121266
Good luck