CT-Derived Perinephric Fat Stranding As A Predictor Of Infectious Complications In Patients With Obstructive Urolithiasis

Background: Infectious complications in patients with obstructive urolithiasis can progress rapidly and require early risk stratification. Perinephric fat stranding (PFS) on non-contrast CT is a common secondary sign of ureteric obstruction, but its diagnostic value in predicting infection remains unclear. Objective: To evaluate the diagnostic utility of CT-detected perinephric fat stranding for predicting infectious complications in patients with obstructive ureteric calculi. Methods: A retrospective observational study was conducted on 35 adult patients with obstructive ureterolithiasis and hydronephrosis identified on non-contrast CT. Patients were stratified based on the presence of infectious complications, defined by clinical, laboratory, and microbiological criteria. Imaging parameters, including presence and pattern of PFS, were assessed. Multivariate logistic regression was used to identify independent predictors of infection, and diagnostic performance metrics were calculated. Results: Infectious complications were present in 16 of 35 patients (45.7%). PFS was significantly more frequent in infected patients (87.5% vs. 47.4%, p = 0.064) and remained an independent predictor of infection in multivariate analysis (adjusted OR 10.52, 95% CI: 1.01–109.5; p = 0.049). Hydronephrosis grade was also independently associated with infection (OR 5.91, p = 0.035). The presence of PFS had a sensitivity of 89%, specificity of 44%, positive predictive value of 65%, negative predictive value of 78%, and an overall diagnostic accuracy of 69%. Diffuse or bilateral PFS was exclusively observed in infected patients. Conclusion: Perinephric fat stranding on non-contrast CT is a sensitive imaging marker for early identification of infectious complications in obstructive urolithiasis. While not specific on its own, PFS may enhance clinical decision-making when combined with laboratory and clinical parameters. Future prospective studies are warranted to validate these findings in larger cohorts.