Medline ® Abstracts for References 1-6

Renal biopsies from 40 patients with hypokalemia and hyponatremia of an average of 10 years' duration due to abuse of laxatives or diuretics, anorexia nervosa, or chronic vomiting were examined with morphometric methods. Light microscopy revealed the following alterations in the renal cortex as compared with 36 normal kidney: JGC were sometimes slightly and sometimes enormously enlarged (mean, 217%). Smaller glomeruli were found with reduction in the area of the glomerular capillaries and of Bowman's capsule (+/- 7%) but an increase in the area of the mesangial matrix by 25%. The proximal and distal tubules contained nonspecific vacuoles in only 8 of 40 biopsy specimens. Only minor, age-dependent arteriolosclerosis was demonstrable. In 75% of the cases, the interstitial surface area was increased (by 107%) with predominantly focal lymphocytic cellular infiltration. Interstitial fibrosis was more pronounced in emaciated patients. The morphologic-functional correlation between the increase of interstitial surface area and the rise in serum creatinine concentration was highly significant. Typical kaliopenic nephropathy is therefore detectable by light microscopy. GFR impairment correlates with the extent of interstitial fibrosis.

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 cytogenesis 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.