Calcium Oxalate Bladder Stones
Calcium Oxalate is the less common type of bladder stone, and it is the hardest to keep from recurring.
Studies show that up to 50% of dogs with calcuim oxalate bladder stones will experience recurrence within three years
And a separate study in Bichons showed that 73% had a recurrence in three years, some more than once. Those are not real good odds. The fact is that these stones have a variety of causes, many of which we can't do much about. For instance, many dogs that develop Calcium Oxalate (CaOx) stones do so because they have an inborn error in their metabolism, and you can't fix that. CaOx stones can not be dissolved by diet, either. While the formation of calcium oxalate stones is poorly understand and undoubtedly involves multiple factors, we do know that there are some strong genetic factors in several breeds, such as Bichons, Miniature Schnauzers, Lhasa Apsos, and Yorkshire terriers, and you can't fix breed either.
However, there is a list of things that can be done
- Check for Cushing's Disease and other conditions that cause high calcium levels. We can fix these diseases, at least some of them...
- Feeding a special diet that has low protein, high fat, and that promotes urination and produces alkaline urine. Science Diet's U/D is the first choice because it has been shown to reduce the recurrence of CaOx stones. (The key word here is "reduce." It's not 100%.) Royan Canin's S/O is a second choice for those dogs who don't do well on U/D, but it often requires potassium citrate to make the urine alkaline enough. While you can't dissolve CaOx stones with diet, you can definitely help reduce their recurrence with diet.
- Make the urine dilute by feeding canned food instead of dry and possibly adding water to it. The urine needs to have a specific gravity below 1.020
- Encourage frequent urination. Oftener is better.
- Be sure the urine pH is over 6.5. U/D is pretty good at this, S/O less so. If necessary, we can add potassium citrate at 75 mg/kg twice daily. You can monitor urine pH with test strips at home.
- Monitor urine specific gravity and pH closely. Check these 2 values several different times a single day every 1-3 weeks. It is important that the specific gravity and pH goals are met during all hours of the day in order to keep crystal formation at a minimum. Once goals are met, urine can be analyzed less frequently e.g. every 2 weeks for several weeks, and then once a month for a while, and then every 2 months or so for the rest of the dog’s life.
- Have X-rays taken every three to six months. If we can find the stones while they are small enough to flush out, surgery can be avoided. Since taking x-rays is not inexpensive, it may be more cost-effective to not do x-rays and just do surgery again if needed, as four x-rays and a flushing procedure will cost as much if not more than a surgery.