Morphologic aspects of low-potassium and low-sodium nephropathy

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.