Felis ISSN 2398-2950

Dietetic diet: decreasing risk of oxalate stones (uroliths)

Contributor(s): Marge Chandler

Pathophysiology

  • Calcium oxalates are the second most common urolith in dogs and may be the most common in cats; they are usually located within the bladder, but may also be found in the kidneys and ureters.
  • The formation of calcium oxalate uroliths is poorly understand and undoubtedly involves multiple factors. Oxalates are produced by the metabolism of glyoxalate and ascorbate in the liver and excreted in urine. For these uroliths to form, the urine must be supersaturated with calcium.
  • Factors that can affect the urinary supersaturation of calcium may include hypercalcemia   Hypercalcemia: overview  (although serum calcium is often normal   Blood biochemistry: total calcium  ) and possibly a diet containing high protein, high calcium, and low vitamin B6.
  • While hypercalciuria is a significant risk factor, it does not necessarily always cause calcium oxalate urolith formation in human beings, dogs, and cats. The solubility of calcium oxalate crystals is not directly influenced by urine pH within the physiologic range, but acidosis may increase the amount of calcium released from the bones to buffer the acid, resulting in hypercalciuria.
  • Diuresis (resulting in decreased urine concentration) decreases the risk of calcium oxalate urolithiasis in people. Similarly, cats consuming canned (high moisture) diets have 1/3 the risk of cats on drier food. Formation of more dilute urine lowers the risk of supersaturation.
  • One of the natural inhibitors of calcium oxalate crystal growth, nephrocalcin, has been found to be defective in the urine of dogs with calcium oxalate uroliths. Nephrocalcin reduces the opportunity of calcium oxalate crystals to grow or aggregate. Other potential inhibitors include citrate, glycosaminoglycans, Tamm-Horsfall proteins, and osteopontine.
  • In humans, a stressful life and obesity have also been associated with more urinary stone problems.
  • Treatment of clinically significant uroliths is usually by surgery   Urolithiasis  . Prevention of reoccurrence includes treatment of any underlying cause of hypercalcemia, treatment of concurrent disease (eg hyperadrenocorticism   Hyperadrenocorticism  ), and increasing water intake and formation of dilute urine by dietary adjustments (and possibly with thiazide diuretics, if necessary), and appropriate diet.

Dietary requirements to dissolve or decrease the risk of oxalate stone

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Special considerations

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Recipes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Lulich L P, Osborne C A, Carvalho M et al (2012) Effects of a urolith prevention diet on urine compositions of glycosaminoglycans, Tamm-Horsfall glycoprotein, and nephrocalcin in cats with calcium oxalate urolithiasis. Am J Vet Res 73 (3), 447-451 PubMed.
  • Palm C A, Westropp J L (2011) Cats and calcium oxalate: strategies for managing lower and upper tract stone disease. J Feline Med Surg 13 (9), 651-660 PubMed.
  • Bartges J W, Kirk C, Lane I F (2004) Update: Management of calcium oxalate uroliths in dogs and cats. Vet Clin North Am Small Anim Pract 34 (4), 969-87, vii PubMed.

Other sources of information

  • Bartges J, Kirk C (2007) Nutrition and Urolithiasis. ACVIM Proceedings 2007.
  • Bartges J, Kirk C (2007) Nutrition and Urinary Tract Disease - Myths and Legends. ACVIM Proceedings 2007.


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