Feline urethral plugs
Since 1981, struvite has consistently been the most common mineral in feline urethral plugs (Figures 3 through 5, Table 1).
The prevalence of calcium oxalate in urethral plugs consistently has been infrequent (< 1 percent). For example, 645 urethral
plugs were submitted to the Minnesota Urolith Center in 2003. The mineral composition of approximately 87 percent of the plugs
was primarily struvite (Figure 3). Less than 1 percent were composed of calcium oxalate.
Table 1: Mineral composition of 11,697 feline uroliths and 415 urethral plugs submitted to the Minnesota Urolith
Center during 2009*
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. Whatever the reasons, the dominant presence of struvite in urethral plugs is of clinical significance
in terms of selection and timing of dietary strategies to prevent their formation.
Continued study and research are necessary to identify and monitor ongoing or new trends. Veterinarians are encouraged to
send all uroliths and urethral plugs to the Minnesota Urolith Center for analysis and inclusion in epidemiologic investigations.
With the support of an educational gift from Hill's Pet Nutrition, the Minnesota Urolith Center is providing quantitative
urolith analysis at no charge. Online submission, e-mail notification and electronic retrieval of results are available. With
a database of more than 600,000 samples, the veterinary community is offered the latest information on urolith trends, treatment
and prevention suggestions. For details, visit the center's Web site at
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.