Förekomst av hyperaldosteronism hos katter med kroniskt förhöjda njurvärden : med utvärdering av en aldosteron - ELISA för hund och katt

Sammanfattning: Primary hyperaldosteronism is an endocrine disease that recently is suggested to be more common in cats than previously thought, and is suspected to be a contributing factor to the development of chronic kidney disease (CKD) among cats. The clinical signs in cats with primary hyperaldosteronism are similar to those seen in CKD. Both conditions may lead to hypertension, hypokalemia, progressive kidney damage, and proteinuria. Medical therapy is available for primary hyperaldosteronism. Therefore, the differentiation of cats with primary hyperaldosteronism from cats with chronic kidney disease is of clinical importance. Chronic kidney disease is common in cats, but there are few studies on the prevalence of primary hyperaldosteronism in cats. One contributing factor in Sweden may have been the lack of an easily available analysis for aldosterone. The first aim of the present study was to evaluate an aldosterone-ELISA for diagnostic purposes in cats and dogs. The second aim was to compare serum aldosterone concentration between cats with chronic azotemia and nonazotemic cats, and to analyse the correlation between serum aldosterone concentration and blood pressure in cats with chronic azotemia. The aldosteron-ELISA (DRG Diagnostics, Marburg, Germany) were evaluated at the Clinical chemistry laboratory at the Swedish University of Agricultural Sciences in Uppsala. Twentyeight client-qwned cats were included in the study, 14 cats woth chronic azotemia and 14 nonazotemic cats. Blood samples were taken at the University Animal Hospital, Swedish University of Agricultural Sciences. The results of the validation of the aldosterone-ELISA assay showed linearity up to serum concentrations of aldosterone of approximately 600 pmol/l. In dogs and cats, the medium intra-assay coefficient of variation was approximately 8%. The medium inter-assay coefficient of variation was 4.4% in cats and 10.4% in dogs. Elevated serum concentrations of aldosterone (hyperaldosteronism) were found in two (14%) cats with azotemia. To distinguish cats with primary hyperaldosteronism from secondary, measurement of the plasma renin concentration is needed. Plasma renin activity will be determined, but was beyond the scope of the present study. There was no significant difference in serum aldosteron concentration between cats with azotemia and non-azotemic cats. Serum aldosterone concentration in hypertensive cats with chronic azotemia was significantly higher (median, 331 pmol/l; range, 313-332 pmol/l) than in normotensive cats with chronic azotemia (median, 223 pmol/l; range 135-280 pmol/l) (p=0.03, Mann-Whitney-U test). To the author's knowledge, this is the first study on the prevalence of hyperaldosteronism in cats with kidney disease in Sweden. Although the study was small, hyperaldosteronism was demonstrated in a number of cats with azotemia. More studies are needed for improved insight in prevalence and ethiology of hyperaldosteronism in cats.