Ultrasonic examination
apnea
An experienced ultrasound physician (with 16 years of experience in renal ultrasound) performed image acquisition on the day before the patient underwent renal puncture using a Canon ultrasonic system Aplio 700 (Canon Medical Systems, Otawara, Japan) with a 3.5 MHz linear probe (i8C1) during fasting for more than 6 h and apnea at the end of inspiration. In all the participants, the right kidney was examined by ultrasound, having undergone right kidney biopsies. With patients lying on the left side, the ultrasound probe was gently positioned in the right abdomen by oblique projection, and the 3.5 MHz probe was used for kidney ultrasound examination. The probe was placed on the posterior axillary line, the position and angle of the probe were adjusted to obtain a longitudinal image of the kidney, and the two-dimensional image was consecutive collected.The ultrasound scanner was then switched to monochrome SMI mode. The SMI-specific area of interest frame was placed on the whole kidney. The mechanical index was 1.6, the frame rate was 25–35 frames/s, the dynamic range was 65–75 dB, and the SMI speed was 3.5 cm/s. After obtaining the optimal blood flow section of the kidney, the images were continuously collected.