[Evaluation of predictors of chronic kidney disease in hyperthyroid cats following radioiodine treatment - a pilot study].

Currently, no suitable parameter to predict the occurrence of azotaemic chronic kidney disease (CKD) after hyperthyroidism treatment in cats exists. The aim of this study was to evaluate various clinical and laboratory parameters as well as renal cortical thickness (assessed by ultrasound) as predictors of azotaemic CKD after radioiodine therapy (RAIT).Cats presented for RAIT (April 2021-April 2022) were prospectively enrolled. Cats with azotaemia (creatinine≥140 µmol/L) and cats with pathological renal morphology were excluded. After RAIT, cats were followed for 6-12 months (measurement of total thyroxine [TT4], thyroid-stimulating hormone and creatinine). Cats with persistent hyperthyroidism and cats with a follow-up<6 months were excluded from the statistical analysis, as their thyroid and kidney function could not be sufficiently evaluated. Following parameters obtained prior RAIT were compared between cats that developed azotaemic CKD following RAIT and those that did not: age, weight, duration since the diagnosis of hyperthyroidism and RAIT, blood pressure, haematocrit, concentration of creatinine, urea, potassium, phosphate, TT4 and symmetrical dimethylarginine, urine-specific gravity, urine protein/creatinine ratio and sonographically assessed renal cortical thickness.51 cats were enrolled; 29/51 were included in the statistical analysis (11/29 became euthyroid and 18/29 became hypothyroid post RAIT). There was no difference in the frequency of azotaemia between euthyroid and hypothyroid cats (5/11 vs. 6/18, p=0.7). None of the clinical, laboratory and morphological markers proved to be predictive of the development of azotaemic CKD following RAIT.None of the investigated parameters was predictive of the development of azotaemic CKD in hyperthyroid cats after RAIT. Due to the small study population, future larger studies should be undertaken, especially to assess morphological markers.