FOCUSED NUTRITION
Renal & Urinary Disorders
FOCUSED NUTRITION
Helpful information about the unique nutritional needs of dogs and cats with certain lifestyles or health challenges.
Managing Feline Struvite and Calcium Oxalate Urolithiasis
Andy Sparkes
BVetMed, PhD, Diplomate ECVIM, MANZCVS, MRCVS
Simply Feline Veterinary Consultancy
Shaftesbury, Dorset, United Kingdom
Q. What is urolithiasis, and what types of uroliths are common in cats?
A. Urolithiasis is the macroscopic accumulation of crystalloid material (uroliths or “stones”) in the urinary tract. This is distinct from crystalluria (the presence of microscopic crystals in the urine), which is a normal finding in many cats. A variety of urolith types occur in cats, but the most common are “struvite” (composed primarily of magnesium, ammonium, and phosphate) and calcium oxalate (CaOx). Crystalluria is a common finding in healthy cats and, without evidence of urolithiasis, urethral obstruction, or lower urinary tract signs, is not likely to require intervention.
Q. What are common ways to manage urolithiasis in cats?
A. Struvite uroliths can be dissolved medically, whereas CaOx cannot and require removal for resolution.1 The ACVIM consensus guidelines for managing non-obstructive uroliths in cats include:2
- For suspected struvite uroliths, medical dissolution is highly effective and should be attempted unless contraindicated (e.g., urethral obstruction).
- Infected struvite uroliths are rare but require antimicrobial therapy to eliminate the infection.1,2
- Urocystoliths that cannot be dissolved and are not associated with clinical signs can be monitored. They should be removed if they are likely to obstruct the urethra.2
- With CaOx uroliths, hypercalcemia should be investigated and treated appropriately when present.
Q. What management strategies can help reduce recurrence of uroliths?
A. There is a high risk of recurrence of uroliths, so long-term medical management to reduce risks is needed. Several commercially available veterinary urinary diets are designed to dissolve struvite uroliths and to help prevent recurrence of both struvite and CaOx. A number of these diets have proven efficacy in dissolving naturally occurring struvite uroliths.3–6 Chosen diets should be complete and balanced and should be designed to dissolve and help prevent struvite stones and to help prevent calcium oxalate stones.
Increasing water intake and the production of dilute urine (USG <1.025–1.030) is considered the most beneficial intervention and may be achieved by feeding a high moisture (>70–80%) diet. If using a dry diet, choose a diet with moderately increased sodium (e.g., 300–350 mg/100 kcal) to help increase water intake and reduce urinary mineral concentration. Diets alone may not achieve optimum urine dilution and it is valuable to encourage additional water consumption, for example, by using nutrient-enhanced water supplements.
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References
- Bartges, J. W., & Callens, A. J. (2015). Urolithiasis. Veterinary Clinics of North America: Small Animal Practice, 45(4), 747-768. doi: 10.1016/j.cvsm.2015.03.001
- Lulich, J. P., Berent, A. C., Adams, L. G., Westropp, J. L., Bartges, J. W., & Osborne, C. A. (2016). ACVIM small animal consensus recommendations on the treatment and prevention of uroliths in dogs and cats. Journal of Veterinary Internal Medicine, 30(5), 1564-1574. doi: 10.1111/jvim.14559
- Houston, D. M., Weese, H. E., Evason, M. D., Biourge, V., & van Hoek, I. (2011). A diet with a struvite relative supersaturation less than 1 is effective in dissolving struvite stones in vivo. British Journal of Nutrition, 106(S1), S90-92. doi: 10.1017/S0007114511000894
- Lulich, J. P., Kruger, J. M., MacLeay, J. M., Merrills, J. M., Paetau-Robinson, I., Albasan, H., & Osborne, C. A. (2013). Efficacy of two commercially available, low-magnesium, urine-acidifying dry foods for the dissolution of struvite uroliths in cats. Journal of the American Veterinary Medical Association, 243(8), 1147-1153. doi: 10.2460/javma.243.8.1147
- Tefft, K. M., Byron, J. K., Hostnik, E. T., Daristotle, L., Carmella, V., & Frantz, N. Z. (2021). Effect of a struvite dissolution diet in cats with naturally occurring struvite urolithiasis. Journal of Feline Medicine and Surgery, 23(4), 269-277. doi: 10.1177/1098612X20942382
- Torres-Henderson, C., Bunkers, J., Contreras, E. T., Cross, E., & Lappin, M. R. (2017). Use of Purina Pro Plan Veterinary Diet UR Urinary St/Ox to dissolve struvite cystoliths. Topics in Companion Animal Medicine, 32(2), 49-54. doi: 10.1053/j.tcam.2017.07.007