THE NATURAL-HISTORY OF NEPHROCALCINOSIS IN PREMATURE-INFANTS TREATED WITH LOOP DIURETICS

Purpose: We investigated the natural history of nephrocalcinosis in pr emature infants treated with furosemide and attempted to identify fact ors to predict infants most at risk. Materials and Methods: We evaluat ed 13 preterm infants in this longitudinal pilot study. During hospita lization and while receiving a loop diuretic nephrocalcinosis develope d in each patient. Patients were divided into groups based on resoluti on (6) and nonresolution (7) according to spontaneous resolution of ne phrocalcinosis at any point during followup. The 2 groups were compare d to each other and to a control group. Results: Mean followup after d iscontinuation of furosemide in the resolution versus nonresolution gr oups was 10.3 and 7.7 months, respectively. Between the 2 groups there was no significant difference in average gestational age, birth weigh t, number of days hospitalized or on furosemide, or total furosemide d ose. Mean calcium-to-creatinine ratio while receiving furosemide at th e time nephrocalcinosis developed was 0.38 in the resolution group but 2.23 in the nonresolution group (p <0.005). Initial calcium-to-creati nine ratio in age matched infants who did not have nephrocalcinosis wa s 0.4. Frank renal stones developed in 2 of the 7 patients without res olution and 0 of the 6 with resolution. When nephrocalcinosis resolved , it was at a mean of 5.2 months following discontinuation of the diur etic. Conclusions: Early data indicate that nephrocalcinosis resolves in approximately 50% of premature infants 5 to 6 months after disconti nuation of furosemide. The only factor that appears to be predictive o f the infants who will have resolution is the calcium-to-creatinine ra tio when nephrocalcinosis is diagnosed. In patients without resolution this ratio is much higher than in age adjusted normal controls, while in those with resolution it appears normal for age.