ORIGINAL ARTICLE Renal resistive index by transesophageal and transparietal echo-doppler imaging for the prediction of acute kidney injury in patients undergoing major heart surgery Giuseppe Regolisti 1 • Umberto Maggiore 1 • Carola Cademartiri 1 • Loredana Belli 2 • Tiziano Gherli 2 • Aderville Cabassi 1 • Santo Morabito 3 • Giuseppe Castellano 4 • Loreto Gesualdo 4 • Enrico Fiaccadori 1 Received: 29 October 2015 / Accepted: 13 February 2016 / Published online: 19 March 2016 Ó Italian Society of Nephrology 2016 Abstract Background Acute kidney injury (AKI) following major heart surgery (MHS) is associated with early decrease in renal blood flow and worsened prognosis. Doppler-derived renal resistive index (RRI), which reflects renal vascular resistance, may predict the development of AKI in patients undergoing MHS. Methods We studied 60 consecutive patients (mean age 69.5 years, range 30–88, 41 males) undergoing MHS. We measured RRI, both at the renal sinus and intraparenchy- mally, by transesophageal echo-Doppler ultrasound (TE- ED us ) at anesthesia induction and at the end of surgery in all patients. Additionally, we measured RRI by external transparietal echo-Doppler ultrasound (TP-ED us ) at the following time points: anesthesia induction, end of surgery, 4 and 24 h from cardiopulmonary bypass (CPB) start. We also measured serum neutrophil gelatinase associated lipocalin (NGAL) at the same time points. Results AKI [serum creatinine (sCr) increase C0.3 mg/dl vs. baseline within 72 h] developed in 23/60 (38.3 %) patients, with two requiring dialysis. Systemic hemody- namic parameters were similar in the patients who devel- oped AKI (AKI?) and in those who did not (AKI-). Intraparenchymal RRI at end-surgery was significantly higher in AKI? compared to AKI- patients, both at TE- ED us and TP-ED us (TE-ED us mean difference, p = 0.004; TP-ED us mean difference, p = 0.013; difference between TE-ED us and TP-ED us results, p = 0.066), although the predictive performance was limited with both methods (area under the curve [AUC] of the receiver-operator characteristics: 0.71 and 0.70 for TE-ED us and TP-ED us , respectively). Serum NGAL values were higher in AKI ? than in AKI- patients (anesthesia induction, p = 0.037; end-surgery, p = 0.007; 4 h from CPB start, p = 0.093; 24 h from CPB start, p = 0.024. However, combining RRI with serum NGAL at end-surgery did not provide a clear-cut advantage in predicting AKI. Conclusions In patients undergoing MHS, increased echo-Doppler ultrasound-derived RRI at end-surgery is significantly associated with the risk of AKI, but has lim- ited practical utility for identifying the patients who will develop AKI. Keywords Acute kidney injury Á Resistance, vascular Á Echocardiography, transesophageal Á Doppler ultrasound imaging Á Heart surgery Introduction Acute kidney injury (AKI) is a frequent postoperative com- plication in patients undergoing major heart surgery (MHS); its incidence varies according to the different definitions, but Electronic supplementary material The online version of this article (doi:10.1007/s40620-016-0289-2) contains supplementary material, which is available to authorized users. & Giuseppe Regolisti giuregolisti@gmail.com 1 Renal Failure Unit, Department of Clinical and Experimental Medicine, University of Parma, Via Gramsci, 14, 43100 Parma, Italy 2 Heart Surgery Unit, Department of Clinical and Experimental Medicine, University of Parma, Parma, Italy 3 Nephrology and Dialysis Unit, Policlinico Umberto I, University of Rome ‘‘La Sapienza’’, Rome, Italy 4 Nephrology, Dialysis and Transplantation Unit, Department of Emergency and Organ Transplantation, University of Bari, Bari, Italy 123 J Nephrol (2017) 30:243–253 DOI 10.1007/s40620-016-0289-2