The association between chronic kidney disease (CKD) and nephrolithiasis is common. The hypercalciuria is identified as a prominent risk factor. The aims of this study were to evaluate the urinary fractional excretion of calcium (uFECa) in cats with chronic kidney disease (CKD) and without CKD on the presence or absence of nephrolithiasis, and to evaluate associated hypercalciuria factors. The urinary fractional excretion of calcium, urinary creatinine, pH and urinary specific gravity were evaluated in 107 cats that previously underwent ultrasound examination for nephrolithiasis. Blood creatinine values, total calcium, ionized calcium, parathormone and venous hemogasometria were also evaluated. Statistical analysis showed difference among the four groups by Kruskal-Wallis statistic test (p<0.001).

Subsequently, in order to evaluate the differences every two groups, the test performed was Mann-Whitney. P values were defined for comparison between groups by nonparametric Tukey test with α=0.05 significance level. There was statistical difference in the uFECa between cats without CKD groups in the presence of calculi, resulted in a greater uFECa (p=0.036), which is enhanced when compared with the group of cats with CKD and nephrolithiasis (p<0.001), suggesting that there is a tendency of a rise in cats with nephrolithiasis, especially those with CKD, as the box plot below indicates. The results of this study revealed that hypercalciuria is a consistent abnormality in cats with nephrolithiasis and CKD can be considered an aggravating factor.