Introduction

Renal transplant artery stenosis(TRAS) is a relatively frequent complication after transplantation. Patients with a diagnosis of TRAS based on US findings underwent further MRI to refine the diagnosis with quantitative and morphological findings. The hemodynamic studies of TRAS are limited. The aim of current study is to explore the feasibility of arterial spin labeling MRI and 2D phase contrast (PC) Q-flow MRI in evaluating hemodynamic changes of TRAS.

Material and Methods

Sixty-four patients who underwent allograft renal transplantation (40 males, 24 females; age range, 20-61 years; median age, 42 years) between September 2018 and December 2020 were included in this study. All the patients underwent conventional MRI, non-contrast-enhanced magnetic resonance angiography (NC-MRA),3D pseudo-continuous arterial spin labeling(pCASL) imaging and 2D-PC Q-flow imaging were conducted on an Ingenia 3.0T MRI system(Philips Healthcare, the Netherland). The scanned objects contained renal allograft and transplant renal artery. The degree of TRAS (0, no stenosis; 1, 0<stenosis≤50%; 2, 50%<stenosis<75%; 3, stenosis≥75%) was evaluated in the NC-MRA images. The renal allograft perfusion was evaluated in the ASL images. The mean flux and velocity of the stenotic segment of transplant renal artery were calculated using the Q-flow software. Differences in renal allograft perfusion and the mean flux and velocity of the stenotic segment of transplant renal artery among the different TRAS degrees were determined using the non-parametric Kruskal-Wallis test. The relationship between the degree of TRAS with renal allograft perfusion and the mean flux and velocity of the stenotic segment of transplant renal artery was assessed by Pearson correlation coefficients.

Results:

For no stenosis, the renal allograft perfusion was 223.89±64.77 ml/100g/min, the mean flux was 0.06±0.01 ml/s, and the mean velocity was 0.59±0.02 cm/s. For 0<stenosis≤50%, the renal allograft perfusion was 188.02±79.32 ml/100g/min, the mean flux was 0.11±0.23 ml/s, and the mean velocity was 3.53±0.11 cm/s. For 50%<stenosis<75%, the renal allograft perfusion was 96.45±45.05 ml/100g/min, the mean flux was 0.45±0.17 ml/s, and the mean velocity was 8.66±0.35 cm/s. For stenosis≥75%, the renal allograft perfusion was 47.40±23.98 ml/100g/min, the mean flux was 1.18±0.26 ml/s, and the mean velocity was 12.31±0.28 cm/s. The degree of TRAS was strongly correlated with the mean flux and velocity of the stenotic segment of transplant renal artery (r=0.701, P<0.001; r=0.722, P<0.001), and was moderately correlated with renal allograft perfusion (r=0.659, P=0.017).

Conclusion

Arterial spin labeling MRI and 2D PC Q-flow MRI can be used to non-invasively assess hemodynamic changes of TRAS.

Acknowledgements

None.