Association of perinephric fat stranding with CT severity scores and mortality in COVID-19 patients

Aims: To investigate the relationship between the presence of perinephric fat stranding (PFS) with three consecutive chest CT severity scores (CT-SS), mortality and intensive care unit admission in COVID-19 patients. Methods: This single-center retrospective study, included 457 (?18 years) COVID-19 patients with positive RT-PCR tests. A radiologist calculated three consecutive CT-SS for COVID-19 pneumonia using a visual scoring system ranging from 0 to 25 points. Grades of PFS on CTs were defined as none, mild, moderate or severe. Firstly, patients were divided into two groups, with and without PFS. The Association of PFS with demographic and laboratory data, CT-SS, and mortality rates were analyzed. We divided patients into four subgroups based on PFS grading and investigated temporal changes of mean CT-SS of three consecutive CTs in each PFS subgroup using a paired-sample test and Wilcoxon signed-rank test. Results: Patients with PFS were associated with older age (p<0.001) and had higher CT-SS (p=0.03). We found a particularly strong association between PFS and mortality (p<0.001) and intensive care unit admission (p=0.001). Statistical associations were found between PFS and elevated serum BUN (p=0.004), creatinine (p=0.007), CRP (p=0.02), and ferritin (p=0.005). In multivariate logistic regression analysis, older age was associated with 1.067-fold (p<=0.001), PFS 1.964-fold (p=0.007), elevated serum creatinine 3.630-fold (p=0.005) higher risks of mortality. In PFS subgroups other than severe, there were significant increases between the first and second CT-SS (p<0.001, p<0.001, p=0.003). Conclusion: Perinephric fat stranding is an important CT finding that can alert clinicians to the poor prognosis of COVID-19 patients in early periods.