The Application of Contrast-enhanced Ultrasound in Acute Kidney Injury in ICU

The goal of this study is to quantitatively assess renal microcirculation changes by contrast-enhanced ultrasound and to obtain systemic hemodynamic information by ultrasound Doppler at the same time, to analyze the relationship between renal microcirculation changes and systemic hemodynamic changes, and to explore its predictive value in renal function recovery in patients with critical acute kidney injury. The main questions it aims to answer are: 1. To explore the quantitative parameters of contrast-enhanced ultrasound which can reflect the changes of renal microcirculation. 2. To explore the relationship between renal microcirculation and systemic hemodynamics. 3. To explore the value of renal microflow changes quantitatively evaluated by contrast-enhanced ultrasound in predicting renal function recovery.