Abstract

Objective: To analyze the predictive value of Renal Resistance Index (RRI) and Plasma Cystatin C (pCysC) in Pregnancy-Related Acute Kidney Injury (PR-AKI).

Methods: This study included 182 pregnant women admitted to the Intensive Care unit (ICU) between May 2016 and June 2021. Intensivists who had received full-time bedside ultrasound Doppler training performed RRI measurements, and blood was drawn to monitor Serum creatinine (Scr) and pCysC concentrations. The study continued for 3 consecutive days, marked as the first day, the second day, and the third day, during which the hourly urine output (UO) was monitored and recorded. According to the AKI diagnostic staging criteria, patients with AKI were divided into stages I, II, and III and comprised the study group (Group A), and patients without AKI served as the control group (Group B).

Results: Of the 182 enrolled patients, 35 (19.2%) were diagnosed with AKI, including 23 (65.7%) with stage I, 9 with stage II (25.7%), and 3 with stage III (8.6%). Three were excluded owing to the requirement of continuous blood purification. Therefore, 179 patients, 32 in Group A and 147 in Group B, were included. The Scr, pCysC, and RRI of Group A increased on the first, second, and third days, but there was a gradual decrease over time. Each period was compared with the corresponding period in Group B, and there were significant differences (P<0.05). All patients in Group A met the diagnostic criterion of Scr concentration in AKI, and only 34.4% of the patients met the diagnostic criterion of UO. According to the D1 monitoring results, the proportions of increased pCysC and RRI in Group A were 87.5% and 81.3%, respectively. They were significantly different from those in Group B (P<0.001). The three variables of pCysC, RRI, and the combination of pCysC and RRI all independently correlated with AKI. The sensitivity and specificity of pCysC concentration for the prediction of PR-AKI were 87.5% and 84.35%, respectively, and those of RRI were 81.25% and 76.87%, respectively. The sensitivity and specificity of the combination of the two were 96.88% and 72.11%, respectively. Receiver operating characteristic curve analysis showed that these indicators had a significant predictive power for PR-AKI. Although the length of stay in the ICU and hospital in Group A was longer (P<0.05), there was no difference in hospital mortality between the two groups (P>0.05).

Conclusion: The diagnosis of PR-AKI based only on Scr and UO was insufficient. RRI and pCysC were important supplements for diagnosing PR-AKI, with good sensitivity and specificity. However, combining the two was better.

Keywords: Renal resistance index; Cystatin C; Creatinine; Urineoutput; Pregnancy; Acute kidney injury