The Differences in Clinical Characteristics, Incidence, and Prognosis of Acute Kidney Injury Between Patients with Severe Pneumonia of COVID-19 and non-COVID-19 During the Omicron

Background The clinical characteristics and prognosis of acute kidney injury (AKI) in severe COVID-19 patients infected with the Omicron variant compared to patients with classic severe pneumonia remain unclear. This study aims to evaluate these differences following the adjustment of the “zero-COVID” policy. Methods A retrospective cohort study was conducted using propensity score matching (PSM). We enrolled adult patients with non-COVID-19 severe pneumonia (2016-2021) and severe/critical COVID-19 (Omicron wave, 2022-2023). AKI was defined according to KDIGO criteria based on serum creatinine (SCr). The primary outcome was AKI incidence; secondary outcomes included severe AKI, continuous renal replacement therapy (CRRT) use, and in-hospital mortality. Results A total of 845 non-COVID-19 and 396 severe COVID-19 patients were screened. After 1:1 matching, 300 pairs were analyzed. The incidence of AKI was similar between groups (49.0% in non-COVID-19 vs 51.3% in COVID-19, P = 0.603). However, severe COVID-19 patients had significantly higher rates of severe AKI (34.0% vs 25.7%, P = 0.034), CRRT use (8.7% vs 3.7%, P = 0.017), and in-hospital mortality (29.3% vs 19.3%, P = 0.006). Multivariate analysis showed that Omicron infection was an independent risk factor for in-hospital death (OR = 2.096, 95% CI: 1.231-3.567, P = 0.006) and CRRT use (OR = 5.907, 95% CI: 1.662-20.997, P = 0.006). Conclusions Although the overall incidence of AKI was similar after matching, severe COVID-19 (Omicron) patients suffered from more severe kidney injury and worse clinical outcomes compared to non-COVID-19 severe pneumonia patients.