Epidemiology of feline uroliths and urethral plugs - DVM
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Epidemiology of feline uroliths and urethral plugs

Volume 39, Issue 8

Photo 2: Low-power transmission photomicrograph of matrix-struvite urethral plug depicting struvite crystals (clear spaces) surrounded by matrix.
The sustained increase in occurrence of struvite uroliths from 2003 to 2007 may be associated with decreased use of diets designed to dissolve sterile struvite uroliths as a consequence of the significant increase in occurrence of calcium oxalate uroliths in the 1980s and 1990s. However, it is likely that most of the 5,432 sterile struvite uroliths obtained from cats and submitted to the urolith center in 2007 could have been readily dissolved in two to four weeks by feeding a diet designed to promote formation of urine that is undersaturated with struvite.

Epidemiology of feline urethral plugs

Figure 3
Of 506 urethral plugs submitted to the urolith center by veterinarians in 2007, the mineral composition of approximately 92 percent was primarily struvite, with only 1 percent composed of calcium oxalate (Figure 3 and Table 1). Since 1981, struvite has consistently been the most common mineral in feline urethral plugs (Figure 4), and the prevalence of calcium oxalate in urethral plugs always has been infrequent.

Figure 4
The explanation as to why there have been significant shifts in the prevalence of calcium oxalate and struvite in feline uroliths during the past 25 years, while the prevalence of struvite and calcium oxalate in feline urethral plugs has not significantly changed, is not obvious to us.

Table 1
Whatever the reason(s), the high prevalence of struvite in urethral plugs is of clinical significance in terms of the design of dietary strategies to prevent their formation.

Dr. Osborne, a diplomate of the American College of Veterinary Internal Medicine, is professor of medicine in the Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Minnesota.


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