Objective To explore the value of combined ultrasound parameters, including the hepatorenal index (HRI) and renal resistance index (RRI), with cystatin C (CysC) in monitoring early acute kidney injury (AKI) after liver transplantation.

Methods Perioperative data from 121 liver transplant recipients who received organs from donation after brain death were collected. The HRI and RRI of the recipients were measured on postoperative days 1-7 and at 1 month, and the CysC levels were measured on postoperative day 1. The recipients were divided into the AKI group (n=53) and the non-AKI group (n=68) based on whether AKI occurred within 7 days after operation. The data of the two groups were compared, and the ultrasound parameters before and after recovery in the AKI group were analyzed. The value of combined HRI, RRI and CysC in monitoring AKI was also analyzed.

Results AKI occurred in 53 recipients, with an incidence rate of 43.8%, including 30 cases of stage 1, 18 cases of stage 2, and 5 cases of stage 3. Among them, 49 cases occurred on postoperative day 1, and 4 cases occurred on postoperative day 2. Of these, 43 cases recovered within 7 days after surgery, 8 cases recovered within 2 months after surgery, 1 case was lost to follow-up, and 1 case received renal replacement therapy. The body mass index and preoperative CysC levels were higher in the AKI group than in the non-AKI group, and the operative time was longer in the AKI group than in the non-AKI group. The HRI on postoperative day 1 was lower in the AKI group than in the non-AKI group, while the RRI and CysC levels were higher (all P < 0.05). When AKI occurred, the HRI was lower than the baseline level, and the RRI was higher than the baseline level. As AKI recovered, the HRI gradually increased, and the RRI gradually decreased. The receiver operating characteristic curve analysis showed that the sensitivity and specificity of HRI ≤ 1.12 for predicting AKI were 0.623 and 0.878, respectively, with an area under the curve (AUC) of 0.801. The sensitivity and specificity of RRI ≥ 0.65 for predicting AKI were 0.878 and 0.676, respectively, with an AUC of 0.825. The sensitivity and specificity of CysC ≥ 1.38 mg/L for predicting AKI were 0.736 and 0.882, respectively, with an AUC of 0.851 (all P<0.01). The combination of HRI and CysC (AUC=0.897, P<0.01), RRI and CysC (AUC=0.910, P<0.01), and all three parameters combined (AUC=0.934, P<0.01) were more effective than using each parameter alone.

Conclusions HRI and RRI may be used to monitor the occurrence and recovery of early AKI after liver transplantation. The combination of these two parameters with CysC has a high application value in monitoring early AKI after liver transplantation.