[anonymously]

Some dogs have a genetic predisposition to develop calcium oxalate bladder stones.

“Foods that are high in oxalates usually include plant-based products, such as vegetables, advises Dr. Ron Hines of 2ndChance.info. Avoid feeding Fido foods high in oxalates if your dog has been diagnosed with calcium oxalate stones in the past because they can contribute to their formation.
These include beets, carrots, celery, kale, okra, spinach and collard greens, according to the University of Pittsburgh Medical Center. Organ meats like liver and sardines are also high in oxalates, as are foods that are naturally dangerous to dogs like chocolate, nuts and grapes. Other high-oxalate ingredients include corn and soy, along with the ingredients derived from them, according to Dr. Hines.”
Above is an excerpt from: http://dogcare.dailypuppy.com/foods-cause-oxalate-stones-6238.html