A Struvite RSS Below 1 is Predictive of In Vitro Struvite Dissolution in Dog Urine
World Small Animal Veterinary Association World Congress Proceedings, 2015
E. Sagols1; D. Moniot1; A. Defiez2; E. Faur2; C. Nuns2; H. Billy2; Y. Quéau1
1Research and Development, Royal Canin, Aimargues, France; 2European Regional Laboratory, Royal Canin, Aimargues, France


Relative supersaturation (RSS) measures the risk for crystal formation or dissolution in urine, and has been validated in dogs and cats (Roberston et al. 2002). In cats, struvite RSS < 1 predicts dissolution in vitro (Houston et al. 2011).


The aim of this study was to assess whether sterile canine urine with struvite RSS < 1 leads to in vitro struvite dissolution.


Six healthy adult dogs were fed a dry expanded diet (Royal Canin S/O-Kcal-Control dog) for 10 days: 7 days of adaptation and 3 days of urine collection. The urines of the 6 dogs were pooled: urine pH and concentrations of 10 solutes (Ca2+, Mg2+, Na+, K+, NH4+, phosphate, citrate, sulphate, oxalate and uric acid) were measured to calculate RSS with the software SupersatTM. Urine was distributed into bottles stored at -20°C until dissolution test.

A canine urolith analysed at 100% struvite was immersed on day 0 in a bottle of urine and put in a stove at 38°C under stirring. Twenty-four hours later, the urines were filtered to collect the stone, which was dried and weighed. Every day until running out of urine (25 days), the stone was placed in a new bottle and the procedure restarted to follow the dissolution of the stone.


For each dog and for the pool of urine, the struvite RSS were < 1.

After 25 days, 60% of the struvite had dissolved (Figure 1).

Figure 1
Figure 1

Kinetic of canine struvite stone dissolution in urine with struvite RSS < 1.



A sterile dog urine with struvite RSS < 1 is effective at dissolving struvite uroliths.


Speaker Information
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E. Sagols
Research and Development
Royal Canin
Aimargues, France

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