The overall goal of this procedure is to provide a step-by-step sonographic methodology for detecting kidney dysfunction using a drug-induced nephrotoxicity rat model. This is accomplished by first positioning the ultrasound probe using the rail system and isolating the aorta. Next, the probe angle is adjusted to obtain a full kidney view in the center of the screen and the B-mode image is stored using the highest frame rate possible.
Then, the color doppler acoustic window is opened to isolate the renal artery and renal vein. Finally the pulsed wave or PW yellow indicator line is used to assess flow in the right renal artery and sinistore is used to collect the data at the highest possible frame rate. Ultimately, high resolution ultrasound imaging is used to show hemodynamic changes in the kidney following Cisplatin-induced acute kidney injury.
This method can answer key questions in the renal function monitoring field, such as hemodynamic changes caused by kidney injury. Although this method can provide insight into renal hemodynamics, it can also be appied to other systems, such as mouse models. On Day 0, after anesthetizing the animals according to the text protocol, and applying eye ointment, use a No.40 blade and depilatory cream to remove the hair from the chest.
While monitoring the animal's vital signs, set up a high-resolution MS250 ultrasound system with a center frequency of 21 MHz connected to the active port, and the application preset on kidney. Place the anesthetized animal in a supine position on the platform and using the rail system, position the ultrasound probe midline on the animal at a 90 degree angle to the left parasternal line isolating the aorta. From this position, slide the platform with the animal such that the probe becomes level with the left or right renal artery.
Using the micromanipulators, view the renal artery. Then adjust the probe angle by tilting slightly along the Y axis of the probe to obtain a full kidney view in the center of the screen. Once the renal pelvis and renal artery have been imaged, sinistore the images using the highest frame rate allowed with the probe used.
Next, press the color doppler key on the keyboard to turn on the color doppler acoustic window. Insure that the focus depth lies in the center of the kidney. Use sinistore to record the data at the highest frame rate possible.
To capture images in pulsed wave or PW view, click on the PW key to bring up a yellow indicator line on the screen. Using the PW angle key, place the yellow line in the renal artery at an angle that parallels the directionality of the flow through the vessel, ensuring the doppler angle is less than 60 degrees. In this mode, the acoustic window splits into upper and lower sections.
Use sinistore to capture the image of the waveforms that indicate the velocity of the arterial flow at peak systole and diastole. After imaging, place the animal under a heating lamp in a clean recovery area in sternal recumbency. Continually monitor the animal's vital signs until full recovery from anesthesia before returning it to the housing facility.
Twenty-four hours after carrying out baseline imaging, administer an interperitoneal injection of 10 milligrams per kilogram of Cisplatin in a single dose to the treatment animals. Administer normal saline to the control animals. Following the schedule shown here, and while monitoring the animal's vital signs, carry out ultrasound imaging as demonstrated earlier in the video.
Carry out data anlaysis according to the guidelines in the text protocol. The images presented in this study were taken by a single operator and the imaging data was analyzed by a single investigator. The results showed that Cisplatin-treated animals has serum creatinine ranging from 0.5 to 2.1 at Day 6.
The normal level of creatinine is less than 1.1. The ultrasound images offer a high sensitivity over histological data shown in the following studies. At Day 6, histology demonstrated consistent patterns of acute tubule interstitial injuries in Cisplatin-treated kidneys compared to normal saline-treated animals.
Using high-resolution ultrasound imaging to measure hemodynamic changes in kidney, there was no change in morphology in animals without Cisplatin treatment between Day 0 and 6, while pulsus parvus morphology was detected in Cisplatin treated animals at Day 6. RI stands for Resistive Index and PI stands for Pulsatile Index. The upper limits for normal RI and PI are 0.7 and 1.15, respectively, in rats.
Measuring these indices to assess the hemodynamic changes in the kidney, demonstrated a significant increase in both Cisplatin treated animals at Day 6. While attempting this procedure, it's important to ensure the animal has normal vital signs under anesthesia. After its development, this technique paved the way for researchers in the field of renal ultrasound hemodynamic changes following acute kidney injury.
After watching this video, you should have a good understanding of how to image a kidney using a small animal model of acute kidney injury.
