Hip Position Acutely Affects Oxygenation and Perfusion of Kidney Grafts as Measured by Functional Magnetic Resonance Imaging Methods-The Bent Knee Study

Laila-Yasmin Mani; Maryam Seif; Florence Nikles; Dechen W Tshering Vogel; Gaëlle Diserens; Petros Martirosian; Michel Burnier; Bruno Vogt; Peter Vermathen

doi:10.3389/fmed.2021.697055

Hip Position Acutely Affects Oxygenation and Perfusion of Kidney Grafts as Measured by Functional Magnetic Resonance Imaging Methods-The Bent Knee Study

Front Med (Lausanne). 2021 Aug 10:8:697055. doi: 10.3389/fmed.2021.697055. eCollection 2021.

Authors

Laila-Yasmin Mani¹, Maryam Seif^{2

3}, Florence Nikles², Dechen W Tshering Vogel⁴, Gaëlle Diserens², Petros Martirosian⁵, Michel Burnier⁶, Bruno Vogt¹, Peter Vermathen²

Affiliations

¹ Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
² Departments of Biomedical Research and Radiology, University of Bern, Bern, Switzerland.
³ Spinal Cord Injury Center, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.
⁴ Department of Diagnostic, Interventional and Pediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
⁵ Section on Experimental Radiology, University of Tübingen, Tübingen, Germany.
⁶ Service of Nephrology and Hypertension, Department of Medicine, Lausanne University Hospital, Lausanne, Switzerland.

Abstract

Background: Kidney perfusion and oxygenation are two important determinants of kidney graft function. In kidney transplantation, repeated graft hypoperfusion may occur during hip flexion, for example in the sitting position, due to the progressive development of fibrotic tissue around iliac arteries. The aim of this study was to assess the changes in oxygenation and perfusion of kidney grafts during hip flexion and extension using a new functional magnetic resonance imaging (fMRI) protocol. Methods: Nineteen kidney graft recipients prospectively underwent MRI on a 3T scanner including diffusion-weighted, blood oxygenation level dependent (BOLD), and arterial spin labeling sequences in hip positions 0° and >90° before and after intravenous administration of 20 mg furosemide. Results: Unexpectedly, graft perfusion values were significantly higher in flexed compared to neutral hip position. Main diffusion-derived parameters were not affected by hip position. BOLD-derived cortico-medullary R2^* ratio was significantly modified during hip flexion suggesting an intrarenal redistribution of the oxygenation in favor of the medulla and to the detriment of the cortex. Furthermore, the increase in medullary oxygenation induced by furosemide was significantly blunted during hip flexion (p < 0.001). Conclusion: Hip flexion has an acute impact on perfusion and tissue oxygenation in kidney grafts. Whether these position-dependent changes affect the long-term function and outcome of kidney transplants needs further investigation.

Keywords: BOLD; arterial spin labeling; functional MRI; hip flexion; kidney transplantation; multiparametric magnetic resonance imaging; oxygenation; perfusion.