Calcium oxalate prevention tools
Approximately 50% of dogs will have a recurrence of calcium oxalate calculi within 2-3 years. Some dogs can have recurrent calculi much more frequently. Small breed, male, older dogs are more prone to this type of calculi.
Increasing water intake
Increasing his water intake, if possible. Urine specific gravity should be collected in the morning and should be below 1.020 (ideally below 1.008)
We recommend purchasing a refractometer to monitor the urine specific gravity and adjust the amount of water added to the diet to reach the ideal urine specific gravity
You may purchase one on amazon.com: click here
Monitoring calciuria
Monitor calciuria via urine calcium:creatinine ratio and intervene with hydrochlorothiazide (in dogs) or alendronate (in cats), especially if increased.
Thiazide diuretics promote calcium resorption in the proximal tubule and thereby decrease hypercalciuria.
According to Dr. Eva Furrow's work, hereditary CaOx1 causes hypercalciuria due to decreased resorption of calcium in the distal convoluted tubule. Thiazide diuretics are a specific therapy for this disorder.
Idiopathic CaOx stone formers also often have hypercalciuria, but it is unlikely due to renal leak. While hydrochlorothiazide could still reduce calciuresis in these patients, blood ionized calcium concentration should be measured prior to and after starting this medication.
Monitor calciuria and adjust therapy as needed.
Monitoring ionized calcium
Measuring ionized calcium to rule out ionized hypercalcemia. Measure PTH if ionized calcium is at the upper end of the normal range to help rule out primary hyperparathyroidism.
Vitamin D status and intestinal hyperabsorption of calcium
Most dogs with calcium oxalate calculi have hypercalciuria due to intestinal hyperabsorption. There is a subset of dogs with calcium oxalate calculi that have an increased 25D/24,25D ratio, which suggests decreased vitamin 25D inactivation. Therefore, it is important to measure vitamin D metabolites. It is possible that these dogs may benefit from a low vitamin D diet.
Hereditary calcium oxalate urolithiasis, type I (CaOxl) gene
Hereditary calcium oxalate urolithiasis, type 1 (CaOx1) and type 2 (CaOx2) gene testing should be considered in the following breeds: American Staffordshire Terrier, Border Collie, Boston Terrier, Bullmastiff, English Bulldog, Havanese, Pit Bull, Rotweiller, Staffordshire Bull Terrier. This is an autosomal recessive gene that is exclusively expressed in the kidney and released in urine. It functions to regulate urinary calcium resorption, inhibit crystalization, and contribute to blood pressure and immunity against urinary tract infections. This gene (CaOx1 and CaOx2) is present in 60-65% of English Bulldogs with calcium oxalate uroliths, but it is present in less than 1% of the general English Bulldog population. This mutation has not been identified in French Bulldogs. D/D patients are considered at increased risk for stone formation.
CaOx1 mutation - American Staffordshire Terrier, Border Collie, Boston Terrier, Bullmastiff, Havanese, Rottweiler, and Staffordshire Bull Terrier. Based on the data currently available, most dogs with hereditary CaOx1 (D/D dogs) will form CaOx urinary stones in their lifetime. The average age at stone diagnosis in affected dogs is 3 years old, but some are not diagnosed until middle-aged or geriatric years.
CaOx2 mutation - American Bulldog, Basset Hound, Beagle, Bullmastiff, and English Mastiff. The average age at stone diagnosis in affected dogs is 3-4 years old, but some are not diagnosed until middle-aged or geriatric years. Males with hereditary CaOx2 are at much greater risk for forming stones than affected females. In fact, based on our current data, we believe that most affected female dogs are not diagnosed with stones.
Monitoring urine pH
Controlling his urine pH and maintaining between 7.0-7.5.
I recommend getting a urine pH meter or tape.
Measure urine pH while fasted and after eating twice daily for 2 weeks. Continue to monitor urine pH if possible.
Use potassium citrate depending on the baseline urine pH.
Citrate reduces CaOx crystallization by binding calcium, forming soluble complexes with calcium ions, and increasing the activity of other crystallization inhibitors.
According to Dr. Eva Furrow's work, hypocitraturia has not been reported in dogs, but deficiencies in crystallization inhibitors are common in dogs with idiopathic CaOx stones and are a major feature of Hereditary CaOx1. Therefore, it is very important to use potassium citrate in dogs that are positive for CaOx1.
AVOID potassium citrate that has cranberry. Cranberry can theoretically increase urine oxalate excretion.
iModify dose as needed to maintain urine pH within the goal.
Using potassium citrate is very important in dogs that are positive for the CaOx1 gene mutation.
Feeding a stone prevention diet
Hill's C/D Multicare, and Hills C/D + Metabolic (if overweight) are both low in sodium.
Royal Canin Urinary SO aging 7+ is moderate in sodium.
Royal Canin Urinary SO, Royal Canin Urinary SO Moderate Calorie, and Purina UR are relatively high in sodium.
The rationale for using a high sodium diet is that dietary sodium increases water intake and thereby dilutes urinary calcium and oxalate. On the other hand, sodium decreases urinary calcium resorption by the kidneys, resulting in increased calcium excretion. Short-term trials done in dogs, this effect appears to be canceled out by the increased urine volume, but it is unknown how dogs with idiopathic hypercalciuria respond to sodium supplementation over time. In rodents, a high sodium diet increases CaOx stone risk whereas a low sodium diet decreases risk.(2nd study link) In humans, high sodium diet is a risk factor for CaOx stones development and sodium restriction decreases recurrence rates.
In this case, a high sodium diet may not be needed if it is possible to increase water intake by adding water to the diet.
Diets will increase the interval of stone recurrence when compared to regular dog food.