Renal resistive index for the prediction of augmented renal clearance: a prospective observational study.

Background: Augmented renal clearance (ARC) is frequently observed in ICU patients and is associated with renal vascular changes. We hypothesized that the renal resistive index (RRI) could predict ARC. Secondary objectives included evaluating the correlation between RRI and creatinine clearance (CrCl), identifying risk factors for ARC, and assessing its impact on ICU outcomes such as length of stay and survival.

Methods: This prospective observational study included 108 adult ICU patients without kidney disease, enrolled within 24 h of admission. RRI measurement, 24-h CrCl, and ARC score calculation were performed on the first day of ICU stay. We analysed RRI's accuracy in predicting ARC and investigated associations with clinical variables and outcomes.

Results: RRI demonstrated high predictive accuracy for ARC (AUROC: 0.897, 95% CI 0.836-0.958). ARC prevalence was 38.9%. Significant risk factors for ARC included younger age, SOFA score, vasopressor use, trauma-related admissions, and diuretic use. A moderate negative correlation between RRI and CrCl was observed (r = - 0.541, p < 0.001). RRI showed superior predictive performance compared to the ARC score (p = 0.0008). ARC did not significantly affect ICU length of stay but was associated with improved ICU survival.

Conclusions: RRI is a reliable predictor of ARC in ICU patients and can help identify patients at risk early. Combining RRI with risk factors such as age, trauma-related admissions, and severity of illness may improve ARC detection and guide therapeutic decisions.