what food would be best to prevent crystals re-forming in my dog?

Hi, I have a 4year old female Shih-Tzu and was just after some helpful advice.About 5 months ago my dog started having a fishy smell to her urine and also passing blood with it occasionally. I took her to the vets and they gave her 2 courses of antibiotics and some steroids over 2wks. These had an initial effect but after a few days of the course ending her symptoms returned again. The vet had sent some blood samples off and these came back fine, so he decided the next stage would be to send a urine sample off and also do some xrays and an ultrasound to see if there was anything else going on. All of the internal screenings came back with no concern, but the urine sample showed that she had some crystal formation. The vet put her on Hills S/D food for 9wks and with great affect the blood has stopped (although the smell is a lot better it does still have a slight fishy smell to it). We returned to the vets yesterday and the vet has advised that when the remaining food has gone I should try her back on a high quality normal food with no treats. We need to see how she goes, but if they return then she may have to go on a special food for the rest of her life.She was on James Wellbeloved dry food before as I would prefer to give her dry food to protect her teeth, but from what I've read wet food maybe the way to go. I went to my local pet store and they were very helpful and advised me to get in touch with Nature Diet as that may be a good food for her. I rang them today and the advisor said that either the senior lite one which has a low protein content but of high quality or the sensitive range would be the best for her condition. I just wondered has anyone tried this food for this problem or could they recommend it? Or if anyone could advise me on a different food that could possibly be a good option, preferably I would like an element of dry food but aslongs it helps my fur-baby stay healthy I dont mind.Thanks in advance for any helpful advice, and can I just say that she has never shown any signs of being unwell or distressed, she is still as lively and as happy as ever!.Thank You

I don't know if this will be of much help but my cat had struvite crystals which affected his urinary system so he has special food made by a company called 'canin' I'm pretty sure they do similar stuff for dogs so you might want to have a look :)http://www.royalcanin.co.uk/

you might check out this web site they have a lot of information on kidney issues and some food suggestions http://www.aplus-flint-river-ranch.com/article-prescriptionpetfooddiets.php

preventing urinary stones is an important health issue for owners.Diets high in grain and vegetables produce alkaline urine, which allows certain stones to form.Urinary stones form more easily in concentrated, acidic urine, so while a healthy dogfood diet that helps promote an alkaline urine is step one, Rule #2 is helping to keep your dog's urine neutral and as dilute as possible.Adding a half-teaspoon of salt to the dog's water will encourage the dog to drink more, and keep the urine more diluted.Feeding a wet tinned food will provide more moisture than feeding dry kibble.Supplementing your pet's diet with oral potassium citrate (20-37.5mg/pound body weight) given twice a day is thought to lessen the incidence of calcium oxalate stone formation. 2 foods that are recommended:Hill's Prescription Diet u/d or k/d or Waltham's Royal Canin URINARY SO diet.