Corticomedullary shunting after ischaemia and reperfusion in the porcine kidney?

Abstract

Background Renal perfusion may redistribute from cortex to medulla during systemic hypovolaemia and after renal ischaemia for other reasons, but there is no consensus on this matter. We studied renal perfusion after renal ischaemia and reperfusion. Methods Renal perfusion distribution was examined by use of 153Gadolinium-labeled microspheres (MS) after 2 h (hrs) and 4 h ischaemia of the pig kidney followed by 4 h of reperfusion. Intra-arterial injected MS are trapped in the glomeruli in renal cortex, which means that MS are not present in the medulla under normal physiological conditions. Results Visual evaluation after reperfusion demonstrated that MS redistributed from the renal cortex to the medulla in 6 out of 16 pigs (38%) subjected to 4 h ischaemia and in one out of 18 pigs subjected to 2 h ischaemia. Central renal uptake of MS covering the medullary/total renal uptake was significantly higher in kidneys subjected to 4 h ischaemia compared with pigs subjected to 2 h ischaemia (69 ± 5% vs. 63 ± 1%, p < 0.001), and also significantly higher than in the contralateral kidney (69 ± 5% vs. 63 ± 2%, p < 0.001). Analysis of blood and urine demonstrated no presence of radioactivity. Conclusion The study demonstrated the presence of MS in the renal medulla in response to renal ischaemia and reperfusion suggesting that severe ischaemia and reperfusion of the pig kidney leads to opening of functional shunts bypassing glomeruli.

Renal cortex microperfusion evaluated by laser speckle contrast imaging in an ex vivo perfused kidney model—A proof‐of‐concept study

“…The results of our flow experiment were consistent with those reported by Heeman et al., showing that larger changes in delivered total renal flow were not similar to corresponding changes in renal cortex microperfusion 12 . The lack of correlation between changes in delivered renal flow and changes in rcBFI is possibly explained by differential blood distribution in cortex and medulla, including potential shunting from cortex to medulla 21 . In comparison, Fang et al.…”

“…12 The lack of correlation between changes in delivered renal flow and changes in rcBFI is possibly explained by differential blood distribution in cortex and medulla, including potential shunting from cortex to medulla. 21 In comparison, Fang et al found a clear correlation between the slow increase in pump-delivered total renal blood flow in a pressure controlled NMP system and the corresponding LSCI-measured changes in renal cortex microperfusion during the first hour of reperfusion. 14 Indicating a correlation between the total delivered renal blood flow and LSCI-measured changes in renal cortex microperfusion.…”

The impact of oxygen supply and erythrocytes during normothermic kidney perfusion

“…Beyond that, hypotonus or ischemia are known triggers of flow redistribution from the cortex to the medullary regions in the kidney 34 . The resulting cortical hypoperfusion and heterogeneous flow distribution in peritubular capillaries 35 , create large functional oxygen diffusion distances that are most effectively overcome if physical oxygen partial pressures are high 36 .…”