Primary Hyperaldosteronism in Cats

21 June 2021 – News

Primary Hyperaldosteronism in Cats

In addition to being underdiagnosed, primary hyperaldosteronism is the most common adrenocortical disorder in cats. It mainly occurs in middle-aged and older cats and has been reported as a mediator of progressive renal disease.

This disease may occur due to tumorous or nontumorous mineralocorticoid excess. It is associated with cardiovascular and renal complications both in humans and cats, particularly in cases where there is hyperplasia of zona glomerulosa tissue. Hypokalemia is the most consistent laboratory finding, but hypophosphatemia or hypomagnesemia may be present as well. There is also an increased plasma aldosterone concentration with concomitant decreased plasma renin. In fact, the best screening test for feline primary hyperaldosteronism is the ratio of plasma aldosterone concentration to plasma renin activity.

Ultrasound examination, MRI, and computed tomography scans are used to identify adrenal abnormalities and, in case of neoplasia, to assess metastases and possible extension into vasculature. Their findings should always be interpreted along with biochemical results.

If there is no evidence of metastases, unilateral adrenalectomy is the treatment of choice for confirmed unilateral primary hyperaldosteronism. Hypokalemia should be controlled perioperatively and, after surgery, a generous dietary intake of sodium can be provided to avoid the hyperkalemia secondary to chronic contralateral adrenocortical suppression. In most cases the prognosis is excellent, with no medication required.

In cases where there is bilateral hyperplasia of the zona glomerulosa, a nonresectable unilateral adrenocortical neoplasm, distant metastases, financial limitations, or comorbid conditions surgery may be contraindicated. Medical treatment consisting of mineralocorticoid receptor blocker, potassium supplementation and antihypertensive drugs may be indicated. Nevertheless, as it does not permanently eliminate the mineralocorticoid excess, prognosis is not as positive.

Kooistra H. S. (2020). Primary Hyperaldosteronism in Cats: An Underdiagnosed Disorder. The Veterinary clinics of North America. Small animal practice, 50(5), 1053–1063. https://doi.org/10.1016/j.cvsm.2020.05.007