Acute kidney injury (AKI) is a common finding in Neotatal Intensive Care Units (NICU). Sepsis is one the main causes of AKI in preterm newborns. AKI has been associated with significant death rates. Early detection of the condition is the first step to improving prevention, treatment, and outcomes, while decreasing length of hospitalization, care costs, and morbimortality. AKI may progress to chronic kidney disease (CKD), a condition linked with dialysis and greater risk of cardiovascular disease. This review article aims to discuss cases of AKI in preterm newborns with sepsis, the use of biomarkers in lab workup, and the use of non-conventional biomarkers for the early identification of AKI.

BACKGROUND AND AIMS The aim of the study was to evaluate the early association of urinary cystatin-C (uCysC) (proximal tubular injury biomarkers) with sepsis and longer hospital stay in premature newborns (NBs) with neonatal infection. METHOD This is a prospective study with NBs from Neonatal Intensive Care Unit (nUTI), between August 2019 and September 2020. Three groups were constructed: healthy NBs, NBs with neonatal infection without sepsis and NBs with sepsis. Premature newborns with kidney disease, renal malformation, insufficient data in the medical record, or samples with scarce volume were excluded. Urine samples were collected for biomarkers measurements. Urinary cystatin-C was quantified in the urine and expressed with or without ratio by urinary creatinine to investigate the urinary concentration bias. RESULTS In total, 62 NBs were included: 27 healthy, 24 with neonatal infection without sepsis and 11 with sepsis.  No acute kidney injury (AKI) was found in NBs and 22 (63%) had longer hospital stay (˃ 30 days). Higher levels of urinary cystatin-C, both adjusted for urinary creatinine, were elevated in NBs's sepsis group. Moreover, in NBs with a longer hospital stay, there was an elevated level of urinary cystatin-C, which was capable to predict the need for ˃ 30 days of hospital stay (AUC-ROC = 0.783, P = .01). CONCLUSION Our study demonstrated that kidney tubular damage biomarker, such as uCysC, was associated with early sepsis in premature NBs and was useful to prognosis evaluation.