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Mechanism of the renal response to contrast medium in dogs. Decrease in renal function due to hypertonicity.
Investigative Radiology
|January 1, 1983
Summary
Radiographic contrast media cause renal vasoconstriction through a mechanical mechanism, not hormonal. This effect is linked to increased intrarenal pressure and osmotic forces, impacting glomerular filtration rate and blood flow.
Area of Science:
- Nephrology
- Radiology
- Physiology
Background:
- Radiographic contrast media (CM) and hypertonic solutions are known to induce renal vasoconstriction.
- The precise mechanism underlying this CM-induced renal vasoconstriction remains largely unknown.
- Understanding this mechanism is crucial for mitigating potential renal complications associated with contrast media use.
Purpose of the Study:
- To investigate the mechanism by which radiographic contrast media (CM) induce renal vasoconstriction.
- To differentiate between a mechanical and a hormonal basis for CM-induced renal hemodynamic changes.
- To elucidate the role of intrarenal pressure and osmotic forces in contrast media nephrotoxicity.
Main Methods:
- Anesthetized dogs were used to measure renal blood flow (RBF), glomerular filtration rate (GFR), and filtration fraction (FF).
- Renal length (L), ureteral pressure (UP), and wedged renal venous pressure (VP) were monitored to assess intrarenal pressure and system compliance.
- Responses to intrarenal boluses of CM were compared with norepinephrine (NOREPI), and studies with ureteral occlusion were performed.
Main Results:
- CM administration caused significant reductions in GFR (59%) and RBF (23%), with a decrease in FF (44%).
- Unlike norepinephrine-induced vasoconstriction, CM led to increases in renal length, UP, and VP, suggesting osmotic effects and increased intrarenal pressure.
- Elevated ureteral pressure potentiated the CM-induced decrease in renal perfusion, indicating a mechanical component.
Conclusions:
- The findings suggest that radiographic contrast media induce renal vasoconstriction primarily through a mechanical mechanism.
- Osmotic forces and subsequent increases in intrarenal pressure play a significant role in CM-induced renal hemodynamic alterations.
- These mechanical effects, particularly on Starling forces within glomerular capillaries, likely dominate the observed decreases in filtration fraction and GFR.