STUDY OF RENAL METABOLIC DISTURBANCES RELATED TO RENAL LITHIASIS AT SCHOOL-AGE IN VERY-LOW-BIRTH-WEIGHT CHILDREN

We studied 34 asymptomatic children who were born with a very-low-birt hweight (VLBW) and had no perinatal history of acute renal failure nor treatment with furosemide. The study was done at preschool or school age, looking for echographic changes and renal tubular disturbances wh ich are known to predispose to renal lithiasis. The results were compa red with those of a control group of 18 children who had been born at term with a body weight >2,500 g. One or more renal tubular disturbanc es were found in 64.70% of the VLBW children. Most frequently found we re decreased ammonium excretion in response to furosemide (38.23%), en hanced N-acetylglucosaminidase excretion (35.29%), hypercalciuria (26. 47%), and hypocitraturia (23.53%). Echography revealed renal cortical hyperechogenicity (17.65%) and renal lithiasis (8.82%) in some of the VLBW children. We found a significant positive correlation (r = 0.7) b etween the perinatal level of plasma phosphate and the total amount of H+ excreted in response to furosemide at preschool or school age. Bec ause these renal tubular anomalies may be precursors of future lithias is, and the renal function and echography tests are not invasive, we s uggest that renal tubular function be measured and followed up in ever y VLBW child, particularly when perinatal hypophosphatemia has occurre d.