Acute Kidney Injury

Acute kidney injury (AKI) is relatively common in neonates in the NICU, especially preterm infants. From 9% to 56% of infants may experience some degree of kidney injury with preterm infants being at high risk. Preterm infants are at highest risk of kidney injury because they are born before nephrons are fully formed.

Causes

Kidney injury in neonates is similar to kidney injury in older children and adults. Causes of kidney injury include prerenal, intrinsic renal, and obstructive processes. Most often, a prerenal cause is the culprit due to fluid restriction, dehydration, or hypovolemia and decreased perfusion to the kidney. Adverse effects of medications, such as indomethacin, vancomycin, and gentamicin, are common intrinsic renal causes. Postrenal AKI is usually caused by obstruction (e.g., posterior urethral valves or strictures).

Diagnosis and Management

No consensus definition of AKI exists for neonates. AKI is often a clinical diagnosis because laboratory data for kidney function is not particularly accurate or well-studied in neonates. Low urine output (< 1 mL/kg/hour) and increasing creatinine levels can be indicative of AKI in neonates, although infants can also be polyuric. Typically, the rise in creatinine is seen after the kidney injury has occurred. Management of AKI in neonates is typically supportive and aimed at treating the underlying cause.

Renal Near-Infrared Spectroscopy

Near-infrared spectroscopy (NIRS) is a noninvasive method of measuring tissue oxygenation. Sensors can be placed to monitor renal NIRS, and emerging literature suggests it is a more useful tool than serum creatinine levels and/or urine output for monitoring real-time changes in renal perfusion . The contribution of this technology in improving renal outcomes has yet to be definitively determined, but it is used in a majority of NICUs throughout the United States.