Related Experiment Video
Updated: Aug 9, 2025
A Large Animal Model for Acute Kidney Injury by Temporary Bilateral Renal Artery Occlusion
Published on: February 2, 2021
Gadolinium-enhanced MRI visualizing backflow at increasing intra-renal pressure in a porcine model
Søren Kissow Lildal1, Esben Søvsø Szocska Hansen2, Christoffer Laustsen2
1Department of Urology, Aarhus University Hospital, Aarhus, Denmark.
Introduction:
Intrarenal backflow (IRB) is known to occur at increased intrarenal pressure (IRP). Irrigation during ureteroscopy increases IRP. Complications such as sepsis is more frequent after prolonged high-pressure ureteroscopy. We evaluated a new method to document and visualize intrarenal backflow as a function of IRP and time in a pig model.
Methods:
Studies were performed on five female pigs. A ureteral catheter was placed in the renal pelvis and connected to a Gadolinium/ saline solution 3 ml/L for irrigation. An occlusion balloon-catheter was left inflated at the uretero-pelvic junction and connected to a pressure monitor. Irrigation was successively regulated to maintain steady IRP levels at 10, 20, 30, 40 and 50 mmHg. MRI of the kidneys was performed at 5-minute intervals. PCR and immunoassay analyses were executed on the harvested kidneys to detect potential changes in inflammatory markers.
Results:
MRI showed backflow of Gadolinium into the kidney cortex in all cases. The mean time to first visual damage was 15 minutes and the mean registered pressure at first visual damage was 21 mmHg. On the final MRI the mean percentage of IRB affected kidney was 66% after irrigation with a mean maximum pressure of 43 mmHg for a mean duration of 70 minutes. Immunoassay analyses showed increased MCP-1 mRNA expression in the treated kidneys compared to contralateral control kidneys.
Conclusions:
Gadolinium enhanced MRI provided detailed information about IRB that has not previously been documented. IRB occurs at even very low pressures, and these findings are in conflict with the general consensus that keeping IRP below 30-35 mmHg eliminates the risk of post-operative infection and sepsis. Moreover, the level of IRB was documented to be a function of both IRP and time. The results of this study emphasize the importance of keeping IRP and OR time low during ureteroscopy.
Insights
Intrarenal backflow (IRB) occurs even at low intrarenal pressures (IRP) during ureteroscopy. This study visualized IRB using MRI, showing it depends on both pressure and time, highlighting risks of prolonged procedures.
Area of Science:
- Urology
- Medical Imaging
- Nephrology
Background:
- Intrarenal backflow (IRB) is associated with increased intrarenal pressure (IRP).
- Ureteroscopy irrigation elevates IRP, potentially leading to complications like sepsis.
- Previous understanding suggested IRP below 30-35 mmHg mitigates infection risk.
Purpose of the Study:
- To evaluate a novel method for documenting and visualizing intrarenal backflow (IRB).
- To assess IRB as a function of intrarenal pressure (IRP) and time in a porcine model.
Main Methods:
- Utilized a pig model with ureteral catheterization and an occlusion balloon at the uretero-pelvic junction.
- Regulated irrigation to maintain steady IRP levels (10-50 mmHg) and performed serial MRIs.
- Analyzed harvested kidneys for inflammatory markers using PCR and immunoassay.
Main Results:
- MRI demonstrated Gadolinium backflow into the renal cortex in all subjects.
- First visual damage occurred at a mean of 15 minutes and 21 mmHg.
- 66% of kidney cortex showed IRB after 70 minutes at a mean maximum pressure of 43 mmHg.
- Increased MCP-1 mRNA expression was observed in treated kidneys.
Conclusions:
- Gadolinium-enhanced MRI offers detailed visualization of IRB.
- IRB occurs at lower pressures than previously thought, challenging existing safety thresholds.
- IRB is dependent on both IRP and duration, emphasizing the need to minimize pressure and operative time during ureteroscopy.
