Role of Renal Parenchyma Attenuation and Perirenal Fat Stranding in Chest CT of Hospitalized Patients with COVID-19

Background: Chest CT on coronavirus disease (COVID-19) has been extensively investigated. Acute kidney injury (AKI) has been widely described among COVID patients, but the role of kidney imaging has been poorly explored. The aim of this study is to clarify the role of opportunistic kidney assessment on non-enhanced chest CT. Methods: We collected data on patients with COVID-19 consecutively admitted to our institution who underwent chest CT (including the upper parts of kidneys as per protocol). Three ROIs of 0.5-0.7 cm(2) were positioned in every kidney. The values of renal parenchyma attenuation (RPA) and the presence of perirenal fat stranding (PFS) were analyzed. The primary and secondary outcomes were the occurrence of AKI and death. Results: 86 patients with COVID-19 and unenhanced chest CT were analyzed. The cohort was split into CT RPA quartiles. Patients with a CT RPA <24 HU were more likely to develop AKI when compared with other patients (chi(2) = 2.77, p = 0.014): at multivariate logistic regression analysis, being in the first quartile of CT RPA was independently associated with a four times higher risk of AKI (HR 4.56 [95% CI 1.27-16.44, p = 0.020). Within a mean 22 +/- 15 days from admission, 32 patients died (37.2%). Patients with PFS were more likely to die as compared to patients without it (HR 3.90 [95% CI 1.12-13.48], p = 0.031). Conclusions: Detection of low RPA values and of PFS in COVID-19 patients independently predicts, respectively, the occurrence of AKI and an increased risk for mortality. Therefore, opportunistic kidney assessment during chest CT could help physicians in defining diagnostic and therapeutic strategies.