HISTOLOGICAL LONG-TERM OUTCOME OF FUROSEMIDE-INDUCED NEPHROCALCINOSISIN THE YOUNG-RAT

The long-term prognosis of furosemide-associated nephrocalcinosis in t he infant is still unclear, Although discontinuation of the diuretic o ften results in radiological resolution of the calcifications, functio nal abnormalities may persist. The natural history of the renal histop athology of these patients is yet unknown. In the present study we inv estigated the histological long-term outcome of furosemide-induced nep hrocalcinosis in the young rat. Thirty-six weanling male Sprague-Dawle y rats were divided into three groups: A controls, B furosemide given for 8 weeks, and C furosemide given for 2 weeks followed by 6 weeks of observation. Metabolic studies at the end of the experiment demonstra ted a significant diuretic and natriuretic effect in group B. Kidney h istology showed nephrocalcinosis scores (mean+/-SD) of 0.0+/-0.0 in A, 2.6+/-1.5 in B, and 0.8+/-0.6 in C, with B significantly higher than A and C, and C greater than A. Kidney calcium content in B (3,421.9+/- 2,558.7 mu g/g dry tissue) was significantly greater than in A (310.4/-21.3) and C (1470.1+/-932.2). Another group of 6 rats receiving 2 we eks treatment of furosemide showed a nephrocalcinosis score of 2.2+/-1 .5, not different from group B, and an additional group of 6 rats trea ted with furosemide for 2 weeks and observed for another 12 weeks show ed a score of 1.3+/-0.4, not different from group C. We conclude that most of the renal calcifications induced by furosemide occur during th e early days of treatment and that up to 12 weeks after discontinuatio n of the diuretic, the resolution of the calcifications is only partia l.