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Background: Following human renal allograft transplant primary graft dysfunction can occur early in the postoperative
period as a result of acute tubular necrosis, acute rejection, drug toxicity, and vascular complications. Successful treatment
of graft dysfunction requires early detection and accurate diagnosis so that disease-specific medical and/or surgical
intervention can be provided promptly. However, current diagnostic methods are not sensitive or specific enough, so that
identifying the cause of graft dysfunction is problematic and often delayed. Near-infrared spectroscopy (NIRS) is an
established optical method that monitors changes in tissue hemodynamics and oxygenation in real time. We report the
feasibility of directly monitoring kidney the kidney in an animal model using NIRS to detect renal ischemia and hypoxia.
Methods: In an anesthetized pig, a customized continuous wave spatially resolved (SR) NIRS sensor was fixed directly
to the surface of the surgically exposed kidney. Changes in the concentration of oxygenated (O2Hb) deoxygenated (HHb)
and total hemoglobin (THb) were monitored before, during and after renal artery clamping and reperfusion, and the
resulting fluctuations in chromophore concentration from baseline used to measure variations in renal perfusion and
oxygenation.
Results: On clamping the renal artery THb and O2Hb concentrations declined progressively while HHb rose. With
reperfusion after releasing the artery clamp O2Hb and THb rose while HHb fell with all parameters returning to its baseline.
This pattern was similar in all three trials.
Conclusion: This pilot study indicates that a miniaturized NIRS sensor applied directly to the surface of a kidney in
an animal model can detect the onset of renal ischemia and tissue hypoxia. With modification, our NIRS-based
method may contribute to early detection of renal vascular complications and graft dysfunction following renal
transplant.
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