Dispelling Myths About CaOx Uroliths

Explore these plant- and food-based options for CaOx stone prevention for canine patients.

Therapeutic diets for dogs with urinary disease have simplified its management. Fearing that something “nonprescription” will upset the delicate balance between urinary solutes and their saturation, veterinarians may find themselves administering stern precautions to clients against feeding any “real” or human food, including fruits and vegetables. 

Certainly, preventing recurrence of calcium oxalate (CaOx) urolithiasis in stone-prone dogs can prove difficult, and some caregivers welcome the simplicity of feeding one food to their dog every day for life. They have no urge to dabble in homeopathics, experiment with herbs or turn to culinary solutions through homemade diets or plant-based embellishments. 

Others, however, search high and low for natural remedies and may seek help elsewhere if their veterinarian insists on commercial diets, given consumers’ persistent mistrust of the pet food industry since the Chinese melamine disaster.1

In the absence of a clinically proven medication or foolproof commercial diet, the drive for plant- or food-based options for CaOx stone prevention remains strong.23

As medical professionals know well, a one-size-fits-all approach to urolithiasis prevention rarely holds water. Metabolic abnormalities, foods and urinary tract health all influence lithogenesis, but stone type determines the specific treatment and prevention strategy. The past 10 years have seen a significant increase in canine CaOx urolith formation along with a significant decrease in struvite (infection-caused) stones. 4

Urinary stones comprise crystalline and, at times, noncrystalline solid substances that aggregate when lithogen-containing urine supersaturates. 5 Mineral composition of uroliths requires laboratory analysis, such as that performed by the Minnesota Urolith Center; effective treatment planning flows from knowledge of the entire urolith’s composition. 6

Fresh, Frequent Fluid Intake

Individuals may excrete millions of urinary crystals daily without producing stones. Fluids flushing the urinary tract counter the supersaturation of stone-forming solutes. Ensuring regular intake of clean, fresh water serves as the primary prevention strategy. Providing a water fountain with continuously filtered, fresh and running water encourages drinking, as does setting bowls of fresh water in various sites around the house, and flavoring water with tuna juice or low-sodium bouillon. 

Dog food with higher sodium has become a popular “fix” to impel dogs with urolithiasis to drink more water. While it remains to be determined whether heightened dietary sodium intake elevates the risk of hypertension in cats and dogs, caution is warranted. 7

Usually, healthy dogs can cope with elevated sodium intake by ingesting larger volumes of water. However, dogs lacking access to clean water may develop hypernatremia. Extremely salty diets may decrease food intake, induce nausea and affect potassium balance. 

If a higher sodium intake does turn out to cause hypertension in dogs and cats, end-organ damage can affect the eye, heart, kidney and brain. Furthermore, in human medicine, some consider sodium chloride a uremic toxin independent of its negative impact on blood pressure.
 
A high sodium intake may actually elevate stone risk by reducing renal tubular calcium reabsorption and increasing urinary calcium excretion. 8 Whether the elevation of calcium in the urine heightens the risk of CaOx formation depends in part on how dilute the urine becomes due to increased water intake from salty food.

Veggies!

One frequently heard mantra against human food holds that fruits and vegetables, especially those with higher calcium, cause CaOx stones. While it is true that plants are sources of calcium oxalate, CaOx stones in the urine are not a result of an increased concentration of calcium in the urine, as many incorrectly claim. 9

Calcium in the gut is needed to bind oxalate in order to keep it from being excreted in higher concentrations in the urine. As one human study noted, “Fruit and vegetable intake causes a dilution of lithogenic risk factors in the urine. … Withdrawal of fruits and vegetables may expose even healthy subjects to the risk of developing renal calcium stones, whereas supplementing the diet with these food items might be helpful as a preventive measure in hypocitraturic stone formers.1011

Clients should thus be guided to limit their dogs’ consumption of high oxalate vegetables, not high calcium ones. Furthermore, diets high in fruits, legumes, and vegetables tend to produce more alkaline urine. High protein (i.e., high meat) diets lead to more acidic urine, a pH environment that some say supports CaOx lithogenesis,12 although urinary pH alone does not predict CaOx urolith risk.13

Role for Herbs?

Phytotherapies recommended for dogs and cats with bladder stones include chanca piedra (Phyllanthus niruri), alfalfa, dandelion, goldenseal, horsetail, marshmallow, plantain, Oregon grape, uva ursi, yarrow, maitake mushrooms, corn silk powder, olive leaf and more. 1415 In vitro work has shown that two herbs, Herniaria hirsuta and Phyllanthus niruri, respectively, interfere with adhesion to uroepithelial cells and CaOx crystal aggregation.16 16
Other plant extracts, such as epigallocatachin gallate (EGCG) from green tea and Quercus salicina Blume/Quercus stenophylla Makino may counteract oxalate’s cytotoxic influences on the urinary tract lining through antioxidation, again based on in vitro work. Still other traditional plant products stimulate diuresis.17 Whether these substances effectively prevent CaOx formation in dogs remains untested. 

Limit Vitamin C

Herbal formulations18 sold as urolithiasis prevention aids in dogs and cats often contain both cranberry and ascorbic acid (vitamin C). Companies extol these agents’ ability to acidify the urine, which is likely contraindicated for CaOx urolithiasis. Vitamin C converts to oxalate in vivo and as such should be limited in CaOx stone formers.1920 Whether or not cranberry improves or worsens the urinary environment’s predilection for producing CaOx stones remains unclear.21

Lemon and Dogma

Citrate inhibits calcium-based stones from forming. Alkali citrate raises urinary pH and also forms soluble complexes with calcium, thereby decreasing the saturation of CaOx in urine. Citrus fruits and juices offer a natural, tasty source of dietary citrate. Both grapefruit and apple, but not orange juice, appear to reduce the propensity of CaOx to crystallize.22

Lemon juice, boasting a five-fold higher concentration of citrate over orange juice, significantly increases urinary citrate excretion.23 While dogs may or may not enjoy lemon juice drizzled over their meal, this sort of evidence extrapolated from human research on CaOx prevention strategies counters the dogma that the only food dogs with this condition should eat must come from a factory.

Narda Robinson, DVM, DO, Dipl. ABMA, FAAMA, oversees complementary veterinary education at Colorado State.

1. Michel KE, Willoughby KN, Abood SK, et al. Attitudes of pet owners toward pet foods and feeding management of cats and dogs. JAVMA. 2008;233(11):1699-1703.
2. Butterweck V and Khan SR. Herbal medicines in the management of urolithiasis:  alternative or complementary? Planta Med. 2009;75:1095-1103.
3. Koehler LA, Osborne CA, Buettner MT, et al. Canine uroliths:  frequently asked questions and their answers. Vet Clin Small Anim. 2008;39:161-181.
4. Houston DM and Moore AEP. Canine and feline urolithiasis:  examination of over 50,000 urolith submissions to the Canadian Veterinary Urolith Centre from 1998 to 2008.  Canadian Veterinary Journal. 2009;50:1263-1268.
5. Koehler LA, Osborne CA, Buettner MT, et al. Canine uroliths:  frequently asked questions and their answers. Vet Clin Small Anim. 2008;39:161-181.<
6. Koehler LA, Osborne CA, Buettner MT, et al. Canine uroliths:  frequently asked questions and their answers. Vet Clin Small Anim. 2008;39:161-181.
7. MChandler ML. Pet food safety: sodium in pet foods. Topics in Companion Animal Medicine.  2008;23(3):148-153.
8. MButterweck V and Khan SR. Herbal medicines in the management of urolithiasis:  alternative or complementary? Planta Med. 2009;75:1095-1103.
9. MBladder Stones in Dogs. Obtained at http://www.gopetsamerica.com/dog-health/bladder-stones.aspx on 10-22-10.
10. MMeschi T, Maggiore U, Fiaccadori E et al. The effect of fruits and vegetables on urinary stone risk factors. Kidney International. 2004;66:2402-2410.
11. M Chandler ML. Pet food safety: sodium in pet foods. Topics in Companion Animal Medicine.  2008;23(3):148-153.
12. MHines R. Kidney and bladder stones in dogs and cats. Obtained at http://www.2ndchance.info/calculi.htm on 10-22-10.
13. MKoehler LA, Osborne CA, Buettner MT, et al. Canine uroliths:  frequently asked questions and their answers. Vet Clin Small Anim. 2008;39:161-181.
14. MBladder Stones in Dogs. Obtained at http://www.gopetsamerica.com/dog-health/bladder-stones.aspx on 10-22-10.
15. MUT Strength Stat for Cats and UT Strength Stat for Dogs. Vetri-Science Laboratories, product information. Obtained at http://www.vetriscience.com/sellsheets/UT%20Strength%20STAT.pdf on 10-26-10.
16. MButterweck V and Khan SR. Herbal medicines in the management of urolithiasis:  alternative or complementary? Planta Med. 2009;75:1095-1103.
17. MButterweck V and Khan SR. Herbal medicines in the management of urolithiasis:  alternative or complementary? Planta Med. 2009;75:1095-1103.
18. MUT Strength Stat for Cats and UT Strength Stat for Dogs. Vetri-Science Laboratories, product information. Obtained at http://www.vetriscience.com/sellsheets/UT%20Strength%20STAT.pdf on 10-26-10.
19. MButterweck V and Khan SR.  Herbal medicines in the management of urolithiasis:  alternative or complementary? Planta Med. 2009;75:1095-1103.
20. MMassey LK, Liebman M, and Kynast-Gales SA. Ascorbate increases human oxaluria and kidney stone risk. J Nutr. 2005;135:1673-1677.
21. MButterweck V and Khan SR. Herbal medicines in the management of urolithiasis:  alternative or complementary? Planta Med. 2009;75:1095-1103.
22. MHonow R, Laube N, Schneider A, et al. Influence of grapefruit-, orange-, and apple-juice consumption on urinary variables and risk of crystallization. Br J Nutr.  2003;90:295-300.
23. MButterweck V and Khan SR. Herbal medicines in the management of urolithiasis:  alternative or complementary?  Planta Med. 2009;75:1095-1103.

 

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