Hyperaldosteronism: The Prevalence and Role in Cats with Chronic Kidney Disease
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Introduction- The zona glomerulosa of the adrenal glands produces aldosterone. In primary hyperaldosteronism there is an aldosterone excess due to an adrenocortical tumor or a non-tumoral adrenocortical hyperplasia. A mineralocorticoid excess causes increased sodium retention and an increased potassium excretion. This can lead to muscle weakness or paralysis and acute blindness by ablatio retinae or intraocular bleeding. It is also associated with slowly progressive renal failure. Aim of the study- The aim of the research is to demonstrate that hyperaldosteronism is more common among cats than is assumed and to investigate the prevalence of primary hyperaldosteronism in cats with chronic renal failure. When the disease is diagnosed in an early stage a treatment can be started and the renal damage may be limited. Hypothesis- The prevalence of primary hyperaldosteronism in cats with chronic kidney disease is approximately 10%. Animals- Twenty-one cats kept as companion animal have been examined for this study. After measuring creatinine and thyroxine levels, seven of the twenty-one cats could not be taken into account in the study because of a creatinine level within the reference range (indicating no renal failure is present) or thyroxine levels above the upper reference value (indicating a possible thyroid problem). Therefore fourteen cats were suitable for measurement of plasma aldosterone concentration (PAC) and plasma renin concentration (PRA). Methods- Blood pressure measurements, blood and urine collection and analysis and eye examinations were performed on the cats. Results- There were no significant correlations found. Eight of the cats had a blood pressure >160 mmHg. In six cases the plasma potassium concentration was below the reference values, six cats had an aldosterone-renin ratio above the reference values. The specific gravity of the urine was below the reference values in six cats and in two cats retinal abnormalities were found. Conclusion- Given the limited number of cats examined, no firm conclusions can be drawn. It is necessary to obtain more data in order to determine the prevalence of primary hyperaldosteronism in cats with chronic kidney disease. However, six out of fourteen cats had an aldosterone-renin ratio above the reference value and may have primary hyperaldosteronism.