Urolithiasis typically develops through the aggregation of mineral crystals in urine, which eventually impedes the flow of urine and causes irritation of the urinary mucosa.1 The physiologic and pathological factors involved in urolithiasis depend on the particular type of urolith formed and can be unpredictable. Uroliths take time to fully develop, and subclinical kidney damage and renal dysfunction can occur before urolithiasis of the lower urinary tract is diagnosed, making this a clinically important disease condition in companion animals. Identification of the risk factors that are associated with various types of urolithiasis can be important in the prevention or management of the condition.
Limited information is available on the incidence and prevalence of urolithiasis in the general population of dogs. In Sweden, approximately 0.3% of licensed dogs between 1956 and 1982 were reported to have urolithiasis, whereas in Norway, 0.05% of Kennel Club–registered dogs between 1956 and 1970 were treated for urolithiasis.2 In Germany, the reported prevalence was between 0.5% and 1.0% of the canine population by 1990.3 To our knowledge, there are no reports of the general incidence or prevalence of urolithiasis in dogs in the United States.
Struvite uroliths, composed of magnesium ammonium phosphate hexahydrate, have been the most common uroliths in dogs worldwide since the early 1980s.4–7 Infection-induced struvite uroliths are more common than sterile struvite uroliths and are typically associated with UTI by urease-producing bacteria, such as Staphylococcus spp and less commonly Proteus spp.8 Other factors associated with struvite urolith detection in samples from dogs include age, sex, breed, neuter status, anatomic and functional abnormalities of the urinary tract, diet, urine pH, and metabolic or body water homeostasis abnormalities.7–13 Mean age at diagnosis of struvite urolithiasis in dogs ranges from 4.25 to 5.92 years,10 and females are more commonly affected than males.7–10,13–15 Among dogs with urolithiasis, struvite uroliths are especially common in the following breeds: Cocker Spaniel, Springer Spaniel, Pekingese, German Shepherd Dog, and Dachshund.3,10
Previous studies10,11,13,16–19 have been performed to evaluate risk factors for struvite urolithiasis in dogs on the basis of records from diagnostic laboratories. Although studies from diagnostic laboratories or referral clinics provide useful information, difficulties in identifying optimal comparable controls for inclusion in such studies are a concern. As a consequence, published research on risk factors for urolithiasis has been derived from comparisons between dogs with different urolith types (case-case studies) or from registries that did not include proper control animals. We believe that the factors associated with development of struvite urolithiasis may be better understood when affected dogs are compared with dogs without urolithiasis. Therefore, a need exists to identify factors associated with the development of struvite urolithiasis in a population of dogs examined at general care veterinary hospitals. Such information may potentially lead to clinical interventions that either prevent the development of struvite uroliths or promote their early identification in high-risk dog populations. The objective of the study reported here was to retrospectively identify dietary, demographic, temporal, and clinical factors associated with a first-time diagnosis of struvite urolithiasis among dogs examined at general care veterinary hospitals in the United States.
Urinary tract infection
PetWare, Banfield Pet Hospital, Portland, Ore.
Antech Diagnostics, Irvine, Calif.
Minnesota Urolith Center, Saint Paul, Minn.
PROC GLIMMIX, SAS, version 9.3, SAS Institute Inc, Cary, NC.
1. Adams LG, Syme HM. Canine ureteral and lower urinary tract diseases. In: Ettinger SJ, Feldman EC, eds. Textbook of veterinary internal medicine. 7th ed. St Louis: Elsevier, 2010;2086–2115.
2. Wallerstrom BI, Wagberg TI. Canine urolithiasis in Sweden and Norway—retrospective survey of prevalence and epidemiology. J Small Anim Pract 1992; 33:534–539.
3. Hesse A. Canine urolithiasis—epidemiology and analysis of urinary calculi. J Small Anim Pract 1990; 31:599–604.
4. Bovee KC, McGuire T. Qualitative and quantitative analysis of uroliths in dogs: definitive determination of chemical type. J Am Vet Med Assoc 1984; 185:983–987.
5. Jones BR, Kirkman JH, Hogan J, et al. Analysis of uroliths from cats and dogs in New Zealand, 1993–96. N Z Vet J 1998; 46:233–236.
6. Osborne CA, Clinton CW, Bamman LK, et al. Prevalence of canine uroliths. Minnesota Urolith Center. Vet Clin North Am Small Anim Pract 1986; 16:27–44.
7. Sosnar M, Bulkova T, Ruzicka M. Epidemiology of canine urolithiasis in the Czech Republic from 1997 to 2002. J Small Anim Pract 2005; 46:177–184.
8. Osborne CA, Lulich JP, Polzin DJ, et al. Medical dissolution and prevention of canine struvite urolithiasis—twenty years of experience. Vet Clin North Am Small Anim Pract 1999; 29:73–111.
9. Houston DM, Moore AEP, Favrin MG, et al. Canine urolithiasis: a look at over 16,000 urolith submissions to the Canadian Veterinary Urolith Centre from February 1998 to April 2003. Can Vet J 2004; 45:225–230.
10. Ling GV, Thurmond MC, Choi YK, et al. Changes in proportion of canine urinary calculi composed of calcium oxalate or struvite in specimens analyzed from 1981 through 2001. J Vet Intern Med 2003; 17:817–823.
11. Lulich JP, Osborne CA, Thumchai R, et al. Epidemiology of canine calcium oxalate uroliths—identifying risk factors. Vet Clin North Am Small Anim Pract 1999; 29:113–122.
12. Picavet P, Detilleux J, Verschuren S, et al. Analysis of 4495 canine and feline uroliths in the Benelux. A retrospective study: 1994–2004. J Anim Physiol Anim Nutr (Berl) 2007; 91:247–251.
13. Wisener LV, Pearl DL, Houston DM, et al. Risk factors for the incidence of calcium oxalate uroliths or magnesium ammonium phosphate uroliths for dogs in Ontario, Canada, from 1998 to 2006. Am J Vet Res 2010; 71:1045–1054.
14. Weichselbaum RC, Feeney DA, Jessen CR, et al. Evaluation of the morphologic characteristics and prevalence of canine urocystoliths from a regional urolith center. Am J Vet Res 1998; 59:379–387.
15. Low WW, Uhl JM, Kass PH, et al. Evaluation of trends in urolith composition and characteristics of dogs with urolithiasis: 25,499 cases (1985–2006). J Am Vet Med Assoc 2010; 236:193–200.
16. Ling GV, Franti CE, Ruby AL, et al. Urolithiasis in dogs II: breed prevalence, and interrelations of breed, sex, age, and mineral composition. Am J Vet Res 1998; 59:630–642.
17. Ling GV, Franti CE, Johnson DL, et al. Urolithiasis in dogs IV: survey of interrelations among breed, mineral composition, and anatomic location of calculi, and presence of urinary tract infection. Am J Vet Res 1998; 59:650–660.
18. Ling GV, Franti CE, Johnson DL, et al. Urolithiasis in dogs III: prevalence of urinary tract infection and interrelations of infection, age, sex, and mineral composition. Am J Vet Res 1998; 59:643–649.
19. Osborne CA, Lulich JP, Polzin DJ, et al. Analysis of 77,000 canine uroliths. Perspectives from the Minnesota Urolith Center. Vet Clin North Am Small Anim Pract 1999; 29:17–38.
20. Dohoo I, Martin S, Stryhn H. Case-control studies. In: Veterinary epidemiologic research. Charlottetown, PE, Canada: AVC Inc, 2003; 163–174.
21. Ulrich LK, Bird KA, Koehler LA, et al. Urolith analysis—submission, methods, and interpretation. Vet Clin North Am Small Anim Pract 1996; 26:393–400.
22. DiBartola SP. Clinical approach and laboratory evaluation of renal disease. In: Ettinger SJ, Feldman EC, eds. Textbook of veterinary internal medicine. 7th ed. St Louis: Elsevier, 2010;1955–1969.
23. Dohoo I, Martin S, Stryhn H. Linear regression. In: Veterinary epidemiologic research. Charlottetown, PE, Canada: AVC Inc, 2003; 302–303.
24. Dohoo I, Martin S, Stryhn H. Introduction to clustered data. In: Veterinary epidemiologic research. Charlottetown, PE, Canada: AVC Inc, 2003; 459–472.
25. Dohoo I, Martin S, Stryhn H. Mixed models for discrete data. In: Veterinary epidemiologic research. Charlottetown, PE, Canada: AVC Inc, 2003; 499–520.
27. Ling GV, Ruby AL, Johnson DL, et al. Renal calculi in dogs and cats: prevalence, mineral type, breed, age, and gender interrelationships (1981–1993). J Vet Intern Med 1998; 12:11–21.
30. Stevenson AE, Markwell PJ. Comparison of urine composition of healthy Labrador Retrievers and Miniature Schnauzers. Am J Vet Res 2001; 62:1782–1786.
31. Bartges JW, Osborne CA, Polzin DJ. Recurrent sterile struvite urocystolithiasis in 3 related English Cocker-Spaniels. J Am Anim Hosp Assoc 1992; 28:459–469.
32. Legeros RZ, Shannon IL. Crystalline components of dental calculi—human vs dog. J Dent Res 1979; 58:2371–2377.