Assessment of renal ischemia by optical spectroscopy

Introduction. No reliable method currently exists for quantifying the degree of warm ischemia in kidney grafts before transplantation. We describe a method for evaluating pretransplant warm ischemia time using optical spectroscopic methods. Methods. Lewis rat kidney vascular pedicles were clamped unilaterally in vivo for 0, 5, 10, 20, 30, 60, 90, or 120 min; eight animals were studied at each time point. Injured and contralateral. control kidneys were then flushed with Euro-Collins solution, resected, and placed on ice. 335 nm excitation autofluorescence as well as cross-polarized light scattering images were then taken of each injured and control kidney using filters of various wavelengths. The intensity ratio of the injured to normal kidneys was compared to ischemia time. Results. Autofluorescence intensity ratios through a 450-nm filter and light scattering intensity ratios through an 800-nm filter both decreased significantly with increasing ischemia time (P < 0.0001 for each method, one-way analysis of variance). All adjacent and nonadjacent time points between 0 and 90 min were distinguishable using one of these two modalities by Fisher's protected least significant difference. Conclusions. Optical spectroscopic methods correlate with warm ischemia time in kidneys that have been subsequently hypothermically preserved. Further studies are needed to correlate results with physiological damage and posttransplant performance. (C) 2004 Elsevier Inc. All rights reserved.