Real‐time laser speckle contrast imaging measurement during normothermic machine perfusion in pretransplant kidney assessment

Abstract

ObjectivesNormothermic machine perfusion (NMP) provides a platform for pre‐transplant kidney quality assessment that is essential for the use of marginal donor kidneys. Laser speckle contrast imaging (LSCI) presents distinct advantages as a real‐time and noncontact imaging technique for measuring microcirculation. In this study, we aimed to assess the value of LSCI in visualizing renal cortical perfusion and investigate the additional value of dual‐side LSCI measurements compared to single aspect measurement during NMP.MethodsPorcine kidneys were obtained from a slaughterhouse and then underwent NMP. LSCI was used to measure one‐sided cortical perfusion in the first 100 min of NMP. Thereafter, the inferior renal artery branch was occluded to induce partial ischemia and LSCI measurements on both ventral and dorsal sides were performed.ResultsLSCI fluxes correlated linearly with the renal blood flow (R2 = 0.90, p < 0.001). After renal artery branch occlusion, absence of renal cortical perfusion could be visualized and semiquantified by LSCI. The overall ischemic area percentage of the ventral and dorsal sides was comparable (median interquartile range [IQR], 38 [24−43]% vs. 29 [17−46]%, p = 0.43), but heterogenous patterns between the two aspects were observed. There was a significant difference in oxygen consumption (mean ± standard deviation [SD], 2.57 ± 0.63 vs. 1.83 ± 0.49 mLO2/min/100 g, p < 0.001), urine output (median [IQR], 1.3 [1.1−1.7] vs. 0.8 [0.6−1.3] mL/min, p < 0.05), lactate dehydrogenase (mean ± SD, 768 ± 370 vs. 905 ± 401 U/L, p < 0.05) and AST (mean ± SD, 352 ± 285 vs. 462 ± 383 U/L, p < 0.01) before and after renal artery occlusion, while no significant difference was found in creatinine clearance, fractional excretion of sodium, total sodium reabsorption and histological damage.ConclusionsLSCI fluxes correlated linearly with renal blood flow during NMP. Renal cortical microcirculation and absent perfusion can be visualized and semiquantified by LSCI. It provides a relative understanding of perfusion levels, allowing for a qualitative comparison between regions in the kidney. Dual‐side LSCI measurements are of added value compared to single aspect measurement and renal function markers.

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

“…Furthermore, Fang et al. demonstrated that dual‐side LSCI‐monitoring could be valuable for descriptive perfusion assessment during NMP 14 . By introducing the microembolization model during LSCI monitoring of rcBFI, we demonstrated that besides visually detection of perfusion in the outer renal cortex, it is possible to find a relationship between LSCI signal and changes in renal cortex perfusion.…”

“…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.…”

“…LSCI operates with a large field of view, producing a blood perfusion map in real time 12 . This method has shown feasible for visualization of renal cortex microperfusion, measured as renal cortex blood flow index (rcBFI) with an acquired depth of approximately 1 mm 13,14 …”