Analysis of 36,032 canine cases shows decline in struvite uroliths
Jun 01, 2007
Knowledge of urolith composition is important because contemporary methods of detection, treatment and prevention of the underlying causes of urolithiasis largely depend on knowledge of urolith composition.
The following discussion is based on quantitative analysis of 36,032 canine uroliths submitted to the Minnesota Urolith Center in 2006.
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 reveals a gradual and consistent increase in calcium oxalate uroliths, and a gradual and consistent decline in struvite uroliths (Figure 1).
In fact, by 2003 the prevalence of calcium oxalate (41 percent) was approximately equal to struvite (40 percent). In 2004, calcium oxalate (41 percent) surpassed struvite (39 percent). In 2005, calcium oxalate was detected in 41 percent of urolith submissions while struvite was detected in (38 percent).
Trends in 2006
Risk and protective factors
What is the underlying reason for such a dramatic change in the composition of canine uroliths? Although several hypotheses have been proposed, none has been proven to date. Evidence suggests an interaction between (1) demographic risk factors such as breed, age, gender, anatomy and genetic predisposition, and (2) environmental risk factors such as sources of food, water, exposure to certain drugs and living conditions. Some factors may be protective.
Not all risk and protective factors are of equal importance. It is apparent that each contributing risk or protective factor may play a limited or a significant role in the pathogenesis of urolithiasis. The chance of developing a specific type of urolith when exposed to one or more of the risk or protective factors often is expressed in terms of numerical probabilities (so-called "odds" or "odds ratios").
When used in a qualitative (rather than a quantitative) way, the significance of risk or protective factors should not be assigned an "all or none" or "always or never" interpretation.