The recognition of renal cysts in two patients with chronic hypokalemia and the renal effects of hypokalemia in certain species of animals prompted this study of the possible association of hypokalemia and renal cysts in patients with primary aldosteronism or primary renal potassium wasting. Using CT scans, we studied 55 patients with primary aldosteronism, of whom 24 had cysts (44 percent). The cysts were more frequent in patients with adrenal tumors than in those with idiopathic adrenal hyperplasia. Sixteen of the 26 patients with tumors (62 percent) had renal cysts, which were often multiple and located in the medulla. Lower plasma potassium levels and higher serum aldosterone levels, urinary aldosterone excretion, and plasma renin activity were correlated with the extent of the cystic disease. Sequential observations indicated that prolonged hypokalemia can be accompanied by the development of renal scarring and that the size and number of cysts can decrease markedly in some patients after the removal of an adrenal adenoma. The association of hypokalemia, aldosteronism, and renal cysts was also supported by the finding of multiple medullary cysts in two patients with primary renal potassium wasting. We conclude that chronic hypokalemia is accompanied by enhanced renal cystogenesis and may lead to interstitial scarring and renal insufficiency. Renal cysts are thus dynamic structures whose growth can be influenced by hormonal or pharmacologic interventions. (N Engl J Med 1990; 322:345–51).
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