The role of nutrition in management of canine and feline urolithiasis - DVM
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The role of nutrition in management of canine and feline urolithiasis
Dietary modifications important in medical protocols designed to promote urolith dissolution, prevention

DVM InFocus

  • Diet: The goals of dietary prevention include: 1) reducing supersaturation of urine with calcium oxalate, 2) promoting higher concentrations and activity of inhibitors of calcium crystal growth and aggregation, 3) reducing urine concentration and minimizing urine retention, and 4) reducing exposure to nondietary risk factors. The confines of these proceedings preclude discussion of the complex interaction of various dietary ingredients on the formation and prevention of CaOx uroliths, but has been described elsewhere (1, 2). Epidemiologic and clinical studies indicate that recurrence of CaOx uroliths may be minimized by feeding a nonacidifying high-moisture diet formulated to avoid excessive protein, calcium, oxalate and sodium (3). The diet should contain adequate quantities of phosphorus to minimize renal activation of vitamin D, adequate quantities of magnesium, and adequate quantities of vitamin B6. Avoid supplementation with vitamins C and D. Addition of citrate may be of value.
  • Outcome: Controlled studies designed to evaluate the efficacy of dietary modification in reduction in the occurrence or recurrence of feline CaOx uroliths have not been reported. However, at the University of Minnesota, studies of cats with a history of CaOx uroliths revealed that the aforementioned dietary modifications significantly reduced the magnitude of supersaturation of their urine with calcium oxalate as measured by urine activity product ratios.(4).

Sterile struvite

Experimental and clinical studies have confirmed the effectiveness of a calculolytic diet in dissolving sterile struvite uroliths in cats (1, 2).

  • Diet: Sterile struvite uroliths may be dissolved by feeding an acidifying high moisture diet with reduced quantities of phosphorus and magnesium (Prescription Diet Feline s/d; Hill's Pet Nutrition). Because this feline struvitolytic diet is supplemented with sodium chloride, and because it is formulated to produce aciduria, neither sodium chloride nor urine acidifiers should be given concomitantly.
  • Outcome: In a clinical study of 22 (11 male and 11 female) cats, uroliths composed of sterile struvite dissolved in 20 cats in a mean of 36 days (range, 14 to 141 days).
  • Prevention: Epidemiologic and clinical studies performed at the University of Minnesota indicate that acidification of urine to a pH of approximately 6.0 to 6.3 and consumption of low magnesium diets are effective in preventing recurrence of naturally occurring sterile struvite urocystoliths in male and female cats. No attempt was made to determine whether acidification and/or low magnesium diets were the major factors(s) responsible for beneficial results. We emphasize that reduction of some risk factors for formation of struvite crystals, including promoting formation of less alkaline or more acidic urine, is one of several risk factors for calcium oxalate urolithiasis. Therefore, periodic evaluation of the patient to determine efficacy of dietary management is recommended. If persistent calcium oxalate crystalluria occurs, appropriate adjustments in management should be made.

  • Nutritional management of canine lower tract uroliths

Epidemiology of canine uroliths

Of 28,629 canine uroliths submitted to the Minnesota Urolith Center in 2003, 41 percent (11,608) were struvite, and 40 percent (11,577) were calcium oxalate (table 3, ). Purines comprised 6 percent 1,737) of canine uroliths, and cystine accounted for 1 percent (276).

Infection-induced struvite

Experimental and clinical studies have shown that infection-induced struvite uroliths in dogs may be dissolved with a calculolytic diet and administration of antibiotics (5).

  • Diet: The goal of dietary modification for dogs with infection-struvite uroliths is to increase urine volume and to reduce urine concentration of urea (the substrate of microbial urease), phosphorus, and magnesium. We evaluated a high-moisture (canned) calculolytic diet formulated to contain a reduced quantity of high-quality protein and reduced quantities of phosphorus and magnesium (Prescription Diet Canine s/d; Hill's Pet Nutrition). The diet was supplemented with sodium chloride to stimulate thirst and induce compensatory polyuria. In addition, reduction of urea from dietary protein reduces renal medullary urea concentration and further contributes to diuresis.
  • Antimicrobics: The importance of UTI with urease-producing bacteria in formation of most struvite uroliths in dogs emphasizes the importance of therapy to eliminate or control them. We used therapeutic dosages of antimicrobial agents selected on the basis of antibiotic dilution susceptibility tests. Preference was given to bacteriocidal drugs excreted in high concentration in urine, and with a wide margin of safety between therapeutic and toxic doses. The fact that diuresis reduced urine concentration of antimicrobial agents was considered when formulating antimicrobial dosages.
  • Outcome: The efficacy of the aforementioned diet in inducing dissolution of infected struvite uroliths was been confirmed by


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