Macroscopic renal lesions and corresponding MRI findings following elevated intrarenal pressure with E. coli-inoculated saline in a porcine model

Introduction & Objectives: Elevated intrarenal pressure during retrograde intrarenal surgery (RIRS) is a known risk factor for infection.
Individual susceptibility to infections varies, and long-term effects of increased pressure remain unknown. This study assessed the utility of
non-contrast MRI for detecting intrarenal backflow and evaluated the risk of bacteremia under elevated intrarenal pressure with infected
irrigation.
Materials & Methods: 9 anesthetized female pigs (43–47 kg) had one kidney instrumented with occlusion and pressure-monitoring catheters
(Animal License 2024-15-0201-01688); one was excluded from MRI due to metallic artifacts. Pigs were assigned to control (n=3, saline), lowpressure (LP) (n=3, E. coli–saline), or high-pressure (HP) (n=3, E. coli–saline) groups. Intrarenal pressure was increased and maintained for
60 min. MRI scans were obtained using a 1.5T GE Optima scanner. Heavily T2-weighted 3D FSE sequences (TR 6000 ms, TE 900 ms) were
repeated every 15 minutes for 3 hours. Blood cultures were drawn at baseline and every 30–60 min up to 6 hours. Kidneys were bisected and
examined macroscopically.
Results: Peak pressures were 50, 61, 42 mmHg (control), 45, 36, 35 mmHg (LP), and 63, 75, 150 mmHg (HP), with ≥60 mmHg ≥10 min in the
HP-group. MRI showed global parenchymal hyperintensity at sustained increased pressure relative to baseline and the contralateral kidney.
Focal parenchymal segments exhibiting further hyperintensity were present in all HP-kidneys (3/3), one LP-kidney (1/3), and one control
kidney (1/2). Signal normalized after pressure release. Macroscopy revealed cortical hemorrhagic lesions matching hyperintense segments in
all HP-kidneys (3/3) and none in control or LP-kidneys. Bacteremia occurred in all HP-pigs (3/3), one LP-pig (1/3), and none of the controls.
International Conference on Endourology
;81(S2 )
Conclusions: The results suggest that elevated pressure increases the risk of bacteremia in cases of infected irrigation. Using non-contrast
MRI, we successfully detected pressure related parenchymal changes and corresponding macroscopic renal lesions were found in all HPkidneys. The suspected role of microscopic barotrauma and inflammatory responses in the development of these lesions, as well as the
potential long-term impact on renal function, warrants further investigation. Improved understanding of these phenomena could help optimize
endourological decisions regarding surgical strategies