Calcium oxalate (CaOx) ureterolithiasis has emerged as a cause of feline ureteral obstruction (UO) in the last few years. Several risk factors of UO were identified including hypercalcemia. One study showed that hypocalcemia is frequent in cats with urethral obstruction and hyperphosphatemia has been hypothesized as a causal factor. The aim of this retrospective study was to assess how ionized calcium concentration (iCa) varies in cats with UO after UO management.

Cats with UO (group 1) in which iCa was measured at least three times over a minimal period of 15 days, were enrolled and compared to a control group including cats with CKD (stage IRIS 2 or over: group 2). UO was treated by medical or surgical procedure.

Group 1 included 39 cats and group 2 included 37 cats. At time of diagnosis (D0), there was no difference in median creatinine concentration, median iCa and distribution of hypercalcemic, normocalcemic or hypocalcemic cats between both groups. Median phosphorus concentration was significantly higher in group 1 (73.7 mg/l [32–200] vs 42 mg/l [25–91]) (p< 0.001) at D0.

Over time, a significant increase in proportion of hypercalcemic cats was observed in the group 1 at the end of the study vs at D0: 33.3% [95%CI, 18.5–48.1] vs 12.8% [95%CI, 2.3%–23.3%] (p<0.001). The average time of onset of hypercalcemia in these 13 cats was 50.5 days (range: 2–1170) and amongst them only 2 were hypercalcemic from D0. In group 2 proportion of cats normo- or hypercalcemic did not vary during the study period.

Our results suggest that iCa should be monitored in cats with UO as presence of ionised hypercalcemia could be misdiagnosed at time of diagnosis and becomes evident after UO treatment. These results suggest that concurrent hyperphosphatemia could explain this finding. Identification of ionised hypercalcemia as a potential risk factor for UO is important and should appropriately be managed in these cats.

Disclosures

No disclosures to report.