Renal Arterial Anatomy: Implications for Normothermic Machine Perfusion in Renal Transplantation

Normothermic machine perfusion (NMP) is a novel technology that has shown potential in viability assessment and reconditioning of donor organs. Normothermic machine perfusion is technically more challenging in kidneys with multiple renal arteries (RAs). This study aimed to characterize the anatomical variation in RAs with a view to the development of optimal equipment for RA cannulation in NMP. Magnetic resonance angiograms obtained from all potential living donors at our centre between 2018 and 2022 were evaluated with PACS 3D with vessel analysis. Three independent reviewers measured RA characteristics (number, cross-sectional area, diameter, distance, angulation). A total of 618 kidneys were included for analysis. Kidneys were categorized into five groups based on the anatomical configuration of arteries. 75.4% had a single RA (group one). One quarter of kidneys were found to have multiple RAs, with inferior accessory arteries the commonest variation. Of the 139 kidneys with multiple RAs (24.6%): 5.3% had two equal sized RAs (group two), 5.5% had a superior accessory artery (group three), 11.7% an inferior accessory artery (group four), and 2.1% had three RAs (group five). Left RAs were of larger diameter, but right RAs were longer (p < 0.001). The number of arteries supplying the right kidney significantly predicted the number of arteries supplying the left kidney (β = 0.15). 23.7% of kidneys with two RAs and 30.8% with three RAs had distances between vessels > 28 mm (length of the existing clamp used for perfusion). 19.1% of main RAs had originated from the aorta at angles ≥ 135°. These findings highlight the insufficiencies with existing NMP equipment for cannulation of the RA. A larger clamp may facilitate perfusion of more kidneys with multiple vessels, whilst soft, flexible cannulae are likely to be needed to accommodate the wide range in angulation of RA origin demonstrated.