DVM, PhD/ Professor School of Veterinary Medicine and Animal Science, University of Sao Paulo Sao Paulo, Sao Paulo, Brazil
Abstract: Background – In addition to serum phosphate (sP) and FGF-23, the urinary fractional excretion of phosphorus (uFEP) may be used to evaluate the mineral and bone disorders in chronic kidney disease (MBD-CKD) in cats.
Objective – To evaluate the sP and uFEP in CKD cats (IRIS Stages 2, 3 and 4).
Animals – Cats with CKD with Stage 2 (n= 10), Stage 3 (n= 8) and Stage 4 (n= 6) undergoing conservative treatment in accordance with IRIS guidelines at the Veterinary Teaching Hospital.
Methods – Serum and urine samples were collected at the same time-point to sP and uFEP determinations, after 12-hour fasting. The normal cut off values of sP < 4.6 mg/dL and uFEP < 40% were considered to the analysis. ANOVA and Tukey-Kramer test for multiple comparison were applied (P ≤ 0.05).
Results – CKD cats with Stages 3 and 4 showed lower levels of uFEP (14.86 ± 7.5 % and 11.58 ± 3.15 %, respectively), with higher concentrations of sP (5.66 ± 2.27 mg/dL and 9.60 ± 3.94 mg/dL, respectively). Mean values of sP and uFEP in CKD cats with Stage 2 were 4.41 ± 0.86 mg/dL and 8.71 ± 2.22 %, probably due to the satisfactory phosphate control by feeding renal diets.
Conclusions and clinical importance – Cats in late stage of CKD had decreased phosphaturia and hyperphosphatemia. Prospective studies evaluating sP, FGF-23 and uFEP may help to elucidate whether impaired effect of phosphatonins due to reduced renal mass may mediate hyperphosphatemia in cats with CKD.
