To investigate the perirenal features of septic patients with acute kidney injury (AKI) using non-contrast-enhanced CT performed within 24 hours of admission to the ICU, and then to establish and validate a clinical-image model for diagnosis.

A total of 336 septic patients in the ICU of Zhongda Hospital, Southeast University from December 2016 to October 2020 were retrospectively analyzed. Of these, 251 septic patients admitted from December 2016 to December 2019 were included in the training group, and 85 septic patients admitted from January 2020 to October 2020 were included in the validation group. According to whether the patients were associated with AKI, the training group was divided into a sepsis without AKI group (139 patients) and a sepsis with AKI group (112 patients). Clinical indicators related to AKI were collected, and perirenal features on CT images obtained within 24 hours of admission to the ICU were analyzed. Next, univariate analysis was performed for each variable, and variables with P < 0.05 were included in multivariate logistic regression analysis to find clinical and imaging indicators independently associated with the occurrence of AKI. A clinical-image model for diagnosis was then established and validated.

There were statistically significant differences in the infection source of sepsis, laboratory indicators (increased serum creatinine, increased blood urea nitrogen, serum bicarbonate and estimated glomerular filtration rate) and acute physiology and chronic health evaluation Ⅱ score between the sepsis without AKI group and sepsis with AKI group (all P < 0.05). Among the CT features, the sepsis with AKI group was associated with a higher incidence of left thickened perirenal fascia, a higher relative percentage of left perirenal fat density and thicker left retrorenal fat thickness, as compared with sepsis without AKI group (all P < 0.05). Multivariate logistic regression analysis showed increased serum creatinine [odds ratio (OR) = 40.495, 95% confidence interval (CI) (18.805, 87.200), P < 0.001] and left thickened perirenal fascia [OR = 3.437, 95%CI (1.597, 7.398), P = 0.002] were independent risk factors for AKI in septic patients. The area under the receiver operator characteristic curve of the clinical-image model for diagnosis was 0.894 [95%CI (0.850, 0.929), P < 0.001] in the training group and 0.877 [95%CI (0.788, 0.938), P < 0.001] in the validation group.

The left thickened perirenal fascia, a feature of septic patients on non-contrast-enhanced CT images performed within 24 hours of admission to the ICU, is an independent risk factor for AKI in septic patients. The combination of this feature and an increased serum creatinine level at baseline may suggest the presence of AKI in septic patients.