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Identification of kidneys subjected to preretrieval warm ischemic injury by simultaneous monitoring of glomerular filtration and perfusate flow during hypothermic perfusion preservation.

BACKGROUND
Historically, ex vivo physiological evaluation of cadaveric renal allografts has been limited to assessing perfusate flow (PF) during hypothermic perfusion preservation (HPP). Using a small animal model, we have previously described a method for continuous monitoring of glomerular filtration rate (GFR) during HPP. Our study was undertaken to determine if monitoring GFR and PF during HPP distinguished kidneys subjected to preretrieval warm ischemic (WI) injury more reliably than PF alone.


METHODS
In situ WI was induced in Lewis rats (n=10) by extrinsic occlusion of the suprarenal aorta for 30 min. After in situ cold perfusion and retrieval, the left kidney underwent 16 hr of HPP. Nonischemic (NI) control kidneys (n=10) were retrieved in the absence of suprarenal aortic occlusion. Longitudinal changes in PF, GFR, and filtration fraction (FF) during HPP were compared in WI versus NI kidneys (FF=GFR/PF x 100%).


RESULTS
PF remained the same in both cohorts throughout HPP. GFR, however, increased to a significantly greater degree in WI versus NI kidneys during the first 4 hr of HPP (713+/-401 vs. 26+/-23%, respectively) (P<0.05). The increase in FF at 4 hr was 1203+/-696% in the WI kidneys versus 83+/-46% in the NI controls (P<0.05).


CONCLUSIONS
In contrast to PF alone, measurement of both PF and GFR distinguished kidneys subjected to pre-WI from NI controls. The data provide a means to determine if monitoring of both GFR and PF during HPP will predict short- and long-term renal allograft function more reliably than PF alone.