Results of experimental and clinical investigation have confirmed the importance of dietary modifications in medical protocols designed to promote dissolution and prevention of uroliths.
Table 1: Mineral Composition of Feline Uroliths 2003
The objectives of medical management of uroliths are to arrest further growth and/or to promote urolith dissolution by correcting or controlling underlying abnormalities. For therapy to be most effective, it must promote undersaturation of urine with calculogenic crystalloids by:
1) increasing the urine solubility of crystalloids,
2) increasing the volume of urine in which crystalloids are dissolved or suspended,
3) reducing the quantities of calculogenic crystalloids in urine.
For example, attempts to increase the solubility of crystalloids in urine often include dietary modifications designed to change pH in order to create a less favorable environment for crystallization. Increasing dietary moisture is commonly used to increase the volume of urine in which crystalloids are dissolved or suspended. Change in the composition of dietary ingredients is an example of a method to reduce the quantity of calculogenic crystalloids in urine.
Table 2: Mineral Composition of Feline Plugs 2003
The primary objective of this review is to summarize and apply evidence about nutritional management of urolithiasis derived from experimental and clinical studies of cats and dogs performed at the Minnesota Urolith Center at the University of Minnesota's College of Veterinary Medicine.
Feline lower tract uroliths
Epidemiology of feline uroliths and urethral plugs
Calcium oxalate remained the most common mineral in feline uroliths submitted to the Minnesota Urolith Center during the year 2003 (Table 1). Of 8,822 uroliths submitted to the center in 2003, 47 percent (4,182) were calcium oxalate, and 42 percent (3,726) were struvite. As has been the trend for the past two decades, struvite was most common mineral detected in feline urethral plugs (Table 2). Of 645 urethral plugs submitted to the center in 2003, 86 percent (557) were struvite, and <1 percent (3) were calcium oxalate.
Medical protocols that will promote dissolution of CaOx uroliths in cats are not yet available. Voiding urohydropulsion, lithotripsy or surgery are currently the only practical alternatives for removal of active CaOx uroliths. However, clinical experience indicates that dietary management may minimize recurrence of uroliths or prevent further growth of uroliths remaining in the urinary tract.