A NOVEL METHOD OF SONOGRAPHIC TISSUE PERFUSION MEASUREMENT IN RENAL TRANSPLANTS

Problemstellung: Renal transplants' normal function depends on sufficient parenchymal perfusion. Chronic function loss may be a consequence of transplant vasculopathy – the loss of small parenchymal vessels. Today transplant biopsy is used to diagnose such vascular changes. A non-invasive procedure is wanted to detect and follow up parenchymal vascular changes in renal transplants. We present the novel PixelFlux technique of dynamic (heart action averaged), automatic (software based), quantitative Doppler sonographic tissue perfusion measurement to monitor parenchymal vascular state. Methoden: We investigated renal transplants from 38 renal transplant recipients (2,5 to 27 years) from first to more than nine years after transplantation. Perfusion intensity was measured with a software especially dedicated to tissue perfusion measurements (PixelFlux, www.chameleon-software.de). A reproducible region of interest (ROI) was selected as a parallelogram (extending between outer renal surface and outer border of medullary pyramid and laterally throughout the range of one interlobar artery). This ROI was cut into two horizontal slices encompassing distal (d50) or proximal 50% (p50) with separate perfusion measurements in both slices. Ergebnisse: Perfusion of renal transplant cortical parenchyma was significantly different between the layers (p50 and d50) under investigation. In proximal 50% of cortex mean perfusion intensity was at 1,36cm/s (SD: 0,86cm/s) whereas in distal 50% portion a mean value of 0,60cm/s (SD: 0,52cm/s, p=0,000) was found. We found a significant loss of parenchymal perfusion in the posttransplantation period in the peripheral cortex from 1,06cm/s in the first year to minimal values of 0,39cm/s in the 3 to 5 year interval. In transplants surviving longer, perfusion was stronger: 0,71cm/s more than 9 years after transplantation. A significant drop of parenchymal perfusion was found in patients with elevated serum creatinine (1,36cm/s in cases with normal and 0,82cm/s in such with elevated creatinine at proximal cortical level (p50)) Schlussfolgerungen: The novel Pixelflux-technique is able to monitor noninvasively state of parenchymal transplant vessels in different levels of the vascular tree. A significant loss of peripheral parenchymal perfusion may reflect chronic transplant vasculopathy. Pixelflux therefore could be used to monitor transplant perfusion and could have potential to detect early vascular damage due to immunosuppressive therapy.