Canine urolith update, 2009: Perspectives from the Minnesota Urolith Center

Investigating the changes in composition over the last couple of decades.
Jul 01, 2010

Dr. Carl A. Osborne
Knowledge of the mineral composition of uroliths is important because contemporary methods of detection, treatment and prevention of the underlying causes of urolithiasis are primarily related to knowledge of urolith composition. This discussion is based on quantitative analysis of 47,036 canine uroliths submitted to the Minnesota Urolith Center in 2009.

In 1981, calcium oxalate was detected in only 5 percent of canine uroliths submitted to the Minnesota Urolith Center, whereas struvite (magnesium ammonium phosphate) was detected in 78 percent. However, evaluation of the prevalence of different types of minerals in canine uroliths during successive years revealed a gradual and consistent increase in occurrence of calcium oxalate uroliths and a gradual and consistent decline in the occurrence of struvite uroliths (Figure 1, p. 14S). In fact, by 2003 the prevalence of calcium oxalate (41 percent) was approximately equal to struvite (40 percent).

Table 1
In 2004, calcium oxalate (41 percent) surpassed struvite (39 percent). In 2005, calcium oxalate was detected in 41 percent of the urolith submissions, while struvite was detected in 38 percent. In 2009, the frequency of occurrence of calcium oxalate (41 percent) and struvite (39 percent) remained about the same (Table 1; Figures 1, 2 & 3, p. 14S). Recall that the frequency of feline calcium oxalate and struvite occurrence during the same period was similar. (For additional details related to feline uroliths and feline urethral plugs, see "Epidemiology of feline uroliths and urethral plugs: Update 1981 to 2009" in the June 2010 issue of DVM Newsmagazine.) Why should we care?