Medullary nephrocalcinosis associated with long-term furosemide abuse in adults

Background. The use of furosemide is well recognized as a predisposing fact or of nephrocalcinosis in infants. Although furosemide is widely used for v arious medical conditions in adults, its association with nephrocalcinosis in adults is not well established. Methods. We studied 18 consecutive adult patients (male : female ratio 1 : 17, age range 21-59 years) who habitually took furosemide to control weight or oedema for long periods of time (range 3-25 years). The daily dose of c ontinuous intake of furosemide ranged from 40 to 2800 mg. Nephrocalcinosis was evaluated using renal ultrasonography (US), computed tomography (CT), o r kidney biopsies. Results. Renal US and CT revealed bilateral nephrocalcinosis of the medulla ry pyramids in 15 (83.3%) out of 18 patients. The duration of furosemide ab use was similar between nephrocalcinosis positive (NC(+)) and nephrocalcino sis negative (NC(-)) groups. The daily dose of furosemide was nearly 10 tim es higher in the NC(+) group (range 120-2800 mg, mean 538 mg) than the NC(- ) group (range 40-80 mg. mean 67 mg). All patients showed variable degrees of renal insufficiency and there was no difference in creatinine clearance between the NC(+) and NC(-) groups (P>0.05). Kidney biopsies performed in t hree patients showed focal tubulo-interstitial fibrosis and atrophy and cal cifications were observed in outer medullary tubulo-interstitium. Conclusions. Long-term furosemide abuse can cause medullary nephrocalcinosi s in adults, and the risk of developing of nephrocalcinosis seems to be cor related with the daily dose of furosemide. We suggest that long-term furose mide abuse should be suspected in adult patients when medullary nephrocalci nosis is incidentally detected by US or CT.