Microlithiasis and Nephrocalcinosis in Preterm Neonates. Is the Treatment Necessary? A One-Year Sonographic Follow-up Study

Background: Renal microlithiasis includes renal hyperechogenic deposits in the calyces, pelvis, or ureter with a diameter of less than ۲-۳ mm by ultrasound. Currently, there is no information about the outcome and possible complications of renal calcification in premature infants in Iran. The current study aimed to evaluate its outcome in preterm infants. Methods: A total of ۵۰ preterm infants with microlithiasis and nephrocalcinosis enrolled in study. The follow-up ultrasound was evaluated ۲, ۶, and ۱۲ months after diagnosis. Following the diagnosis, infants were assessed for nephrocalcinosis progression. The group was termed unrecovered if the issue persisted during follow-up, and it was considered recovered if it disappeared on follow-up ultrasound. The neonatal data included gestation age, birth weight, length of hospital stay, age at diagnosis of microlithiasis, and used medications. Results: A total of ۵۰ premature infants with microlithiasis and nephrocalcinosis, including ۱۴ females (۲۸%) and ۳۶ males (۷۲%), were born with an average gestation week of ۳۰.۷۸ ± ۲.۷۸. The mean age of diagnosis was ۲.۶۰ ± ۱.۱۱ months. The average hospital stays at the neonatal intensive care unit) NICU (and neonatal ward were ۲۷.۳۸ ± ۱۶.۰۶ and ۱۰.۵۰ ± ۹.۵۷ days, respectively. At the end of the ۱۲-month study period, renal calcification recovered in ۴۰ (۸۰%) patients. There was no significant difference between the two groups of patients with sustained and recovered microlithiasis in terms of gender, age of onset of renal calcification, gestational age, mean hospital stay in NICU and neonatal ward, use of antibiotics, potassium citrate, and hydrochlorothiazide. A p-value of less than ۰.۰۵ was considered statistically significant for all statistical analyses. Conclusion: The obtained results of the study reveal that a high percentage of premature infants with nephrocalcinosis recovered at the end of the ۱۲-month period, indicating this phenomenon is benign.   Keywords: Aminophylline, Kidney function, Microlithiasis, Nephrocalcinosis, Premature infants