Introduction: Reports from the United States suggest that acute kidney injury (AKI) frequently complicates COVID-19, but understanding of AKI risks and outcomes is incomplete . Additionally, whether kidney outcomes have evolved during the course of the pandemic is unknown .

Methods: We used electronic records to identify COVID-19 patients with and without AKI admitted to 3 New York Hospitals between March 2 and August 25 , 2020 . Outcomes included AKI overall and according to admission week, AKI stage, the requirement for new renal replacement therapy (RRT), mortality and recovery of kidney function . Logistic regression was utilized to assess associations of patient characteristics and outcomes .

Results: Out of 4732 admissions 1386 (29.3 %) patients had AKI . Among those with AKI , 717 (51.7 %) had Stage 1 , 132 (9.5 %) Stage 2 , 537 (38.7 %) stage 3, and 237 (17.1 %) required RRT initiation . In March 536/1648 (32.5 %) of patients developed AKI compared with 15/87 (17.2 %) in August (P <0.001 for monthly trend) whereas RRT initiation was required in 6.9% and 0% of admission, in March and August respectively . Mortality was higher with than without AKI (51.6% vs 8.6 %) and was 71.9% in individuals requiring RRT . However, most patients with AKI who survived hospitalization (77 %) recovered to within 0.3 mg/dL of baseline creatinine . Among those surviving to discharge , 62% discontinued RRT .

Conclusions: AKI impacts a high proportion of admitted COVID-19 patients and is associated with high mortality, particularly when RRT is required . AKI incidence appears to be decreasing over time and kidney function frequently recovers in those who survive.