Renal resistive index as predictor of acute kidney injury after major surgery: A systematic review and meta-analysis

Purpose: To determine the efficacy of Doppler renal resistive index in the prediction of acute kidney injury after major surgery.

Methods: A systematic review and meta-analysis of cohort studies was conducted. Medline (1966-2018), Scopus (2004-2018), Clinicaltrials.gov (2008-2018) and Google Scholar (2004-2018) databases were systematically searched. Prospective studies that examined the diagnostic accuracy of renal resistive index in postoperative acute kidney injury were included.

Results: The meta-analysis was based on 10 studies, including a total number of 911 patients. Patients who developed acute kidney injury presented higher renal resistive index values preoperatively (MD: 0.02, 95% CI: [0.00-0.03]), immediately after surgery (MD: 0.07, 95% CI: [0.04-0.11]) and 24 hours postoperatively (MD: 0.07, 95% CI: [0.04-0.09]). The pooled sensitivity was 81.8%, the specificity 77.6% and the area under the curve 0.866. Fagan's nomogram indicated that the post-test probability was increased to 60.6% (positive test) and decreased to 9.5% (negative test), when the pre-test probability was 30%.

Conclusions: Renal resistive index represents a useful marker with fair performance in the prediction of postoperative acute kidney injury. Future cohorts should establish the optimal timing of measurement and evaluate the most appropriate cut-off value that should be used in the clinical setting.