Study to evaluate calcium oxalate supersaturation in stone-forming and non-stone forming cats

Title: Comparison of urinary calcium oxalate supersaturation, and calcium to creatinine and oxalate to creatinine ratios in calcium-oxalate stone-forming cats and non-stone forming cats.

Kristen Hamilton, DVM (UGA Internal Medicine resident)
Joe Bartges, DVM, PhD, DACVIM (SAIM, Nutrition; UGA Internal Medicine faculty)
Bianca Lourenço, DVM, PhD, DACVIM (SAIM; UGA Internal Medicine faculty)

If interested please contact our Clinical Trials Coordinator Lisa Reno via email ( or phone at 706-296-7818.

Study description: Calcium oxalate (CaOx) urolithiasis (urinary stone disease) is a common cause of upper and lower urinary tract disease in cats. Unlike struvite urolithiasis there currently is no dissolution protocol for CaOx stones, thus management typically involves surgical removal of these stones. Management is primarily concentrated on prevention of stone formation through the use of diets formulated for urinary health. While it is hypothesized that CaOx stone-forming cats have an increased urinary calcium concentration compared to non-stone forming cats, there currently are no studies confirming this relationship. This study aims to evaluate the concentration of urinary calcium in stone-forming cats in comparison to non-stone forming, age-, breed-, and sex-matched cats to determine the importance of urinary calcium in the formation of CaOx stones, and to guide management protocols for reducing stone occurrence.

Inclusion criteria:

  • Cats of any breed, sex, or age
  • Cats with recently removed calcium oxalate uroliths confirmed via quantitative analysis who are not being fed an oxalate preventative diet

Exclusion criteria:

  • Cats with uroliths composed of a mineral other than calcium oxalate, or those with uroliths containing another mineral in addition to calcium oxalate.
  • Cats with hypercalcemia or azotemic kidney disease
  • Cats receiving vitamin D supplementation, bisphosphonates, diuretics, or corticosteroids

Cats with recently removed calcium oxalate uroliths will be included if quantitative stone analysis confirms calcium oxalate as the sole mineral in the stone. Included cats will receive a serum chemistry if not performed previously for case management, and will have a urine sample obtained a minimum of two weeks after urolith removal. Owners will be instructed to not alter the diet during this timeframe, and the urine sample will be collected after an overnight fast. Urinary calcium oxalate saturation will be determined and urine calcium and urine oxalate to urine creatinine ratios will be calculated.

The study will pay for a visit fee, physical examination, serum biochemistry profile, urinalysis, blood ionized calcium concentration, urine chemistry, and shipping costs associated with samples submitted to external laboratories.
Duration of study: This study is currently OPEN.

Potential benefits to veterinary medicine: Results from this study may help guide management protocols for reducing the formation of calcium oxalate stones in cats. A decrease in the prevalence of calcium oxalate urolithiasis will reduce the need for expensive and invasive removal procedures.

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