The current threshold used for oliguria in the definition of neonatal AKI has been empirically defined as 1 ml/kg per hour. Urine output criteria are generally poorly documented, resulting in uncertainty in the most accurate threshold to identify AKI in very preterm infants with known tubular immaturity.

We conducted a bicentric study including 473 very preterm infants (24^0/7–29^6/7 weeks of gestation) born between January 2014 and December 2018 with urine output measurements every 3 hours during the first 7 days of life and two serum creatinine measurements during the first 10 days of life. AKI was defined using the neonatal Kidney Disease Improving Global Outcomes (KDIGO) definition. We tested whether higher urine output thresholds (1.5 or 2 ml/kg per hour) in modified AKI definitions may better discriminate neonatal mortality compared with the current definition.

Early-onset AKI was developed by 101 of 473 (21%) very preterm infants. AKI was diagnosed on the basis of urine output criteria alone (no rise in creatinine) for 27 of 101 (27%) participants. Early-onset AKI was associated with higher risk of death before discharge (adjusted odds ratio, 3.9; 95% confidence interval, 1.9 to 7.8), and the AKI neonatal KDIGO score showed good discriminative performance for neonatal mortality, with an area under the receiver operating characteristic (ROC) curve of 0.68 (95% confidence interval, 0.61 to 0.75). Modified AKI definitions that included higher urine output thresholds showed significantly improved discriminative performance, with areas under the ROC curve of 0.73 (95% confidence interval, 0.66 to 0.80) for the 1.5-ml/kg per hour threshold and 0.75 (95% confidence interval, 0.68 to 0.81) for the 2-ml/kg per hour threshold.

Early-onset AKI was diagnosed on the basis of urine output exclusively for a quarter of the cases. Furthermore, modified AKI definitions that included higher urine output improved the discriminative performance for predicting mortality.

目前新生儿 AKI 定义中用于少尿的阈值根据经验定义为每小时 1 毫升/公斤。尿量标准通常记录很少，导致在已知肾小管不成熟的极早产儿中识别 AKI 的最准确阈值存在不确定性。

我们进行了一项双中心研究，纳入了 2014 年 1 月至 2018 年 12 月期间出生的 473 名极早产儿（妊娠 24 ^0/7 –29 ^6/7周），在生命的前 7 天内每 3 小时测量一次尿量，并测量两次血清肌酐在生命的最初 10 天。AKI 的定义采用新生儿肾病改善全球成果 (KDIGO) 的定义。我们测试了修改后的 AKI 定义中较高的尿量阈值（每小时 1.5 或 2 毫升/千克）是否可以比当前定义更好地区分新生儿死亡率。

473 名极早产儿中，有 101 名 (21%) 出现早发性 AKI。101 名参与者中有 27 名 (27%) 仅根据尿量标准（肌酐不升高）诊断 AKI。早发性 AKI 与出院前较高的死亡风险相关（调整后的比值比为 3.9；95% 置信区间为 1.9 至 7.8），AKI 新生儿 KDIGO 评分显示出对新生儿死亡率的良好判别性能，接收器下面积操作特征 (ROC) 曲线为 0.68（95% 置信区间，0.61 至 0.75）。包括更高尿量阈值在内的修改后的 AKI 定义显示判别性能显着改善，对于 1.5 毫升/千克每小时阈值，ROC 曲线下面积为 0.73（95% 置信区间，0.66 至 0.80），对于 1.5 毫升/千克每小时阈值，ROC 曲线下面积为 0.75（95% 置信区间） ，0.68 至 0。

四分之一的病例仅根据尿量来诊断早发性 AKI。此外，修改后的 AKI 定义（包括更高的尿量）改善了预测死亡率的判别性能。