The objective of this protocol is to investigate the impact of prematurity, with or without associated acute kidney injury (AKI), on the future risk of chronic kidney disease (CKD) by establishing a patient registry and biorepository. Serum and urine samples will be collected serially from premature infants admitted to the neonatal intensive care unit (NICU) at Albert Einstein College of Medicine/Weiler Hospital and subsequently followed in the NICU follow-up and pediatric nephrology ambulatory subspecialty clinics. The biorepository will be linked to a comprehensive clinical database.

This is an observational pilot study to enhance understanding of the pathophysiology and epidemiology associated with effects of AKI in premature infants and the role that neonatal AKI plays in future development of CKD. In eligible preterm infants, blood and urine samples will be collected at pre-specified time points during hospitalization and at outpatient follow-up appointments at 6 months, 1 year, 2 years, and 5 years of age and stored in the biorepository. Blood pressure will be measured and recorded at NICU discharge and at all follow-up visits. A renal ultrasound will be performed to monitor renal growth at 2 and 5 years of age. All data will be entered into a comprehensive clinical database, including laboratory results.

Inclusion Criteria:

• Preterm infants less than 32 weeks/ gestational age admitted to the Neonatal Intensive Care Unit at Weiler Hospital (The Children's Hospital at Montefiore).

Exclusion Criteria:

• Known major congenital anomalies of the kidney and urinary tract (CAKUT) including solitary kidney, cystic dysplasia, multicystic dysplastic kidney, renal hypoplasia, obstructive uropathy
• Other genetic syndromes or medical conditions that preclude enrollment per judgment of the attending neonatologist

Preterm infants less than 32 weeks' gestational age