Functional MRI to quantify perfusion changes of a renal allograft after embolization of an arteriovenous fistula

Abstract

Acute allograft injury was observed in a 37-year-old woman within a few weeks after kidney transplantation. Neither renal ultrasound nor computerized tomography (CT) and magnetic resonance (MR) angiography revealed any anomaly. An MR protocol was then performed including arterial spin labeling and intravoxel incoherent motion diffusion weighted imaging. Both arterial spin labeling and the perfusion fraction in the diffusion weighted imaging showed decreased perfusion compared to reference values. The patient subsequently underwent angiography, where an arteriovenous fistula in the upper calix of the transplant kidney was detected and immediate embolization was performed. A second functional MR, performed one week later, demonstrated a 40% increase in organ perfusion. We conclude that functional MR with arterial spin labeling and intravoxel incoherent motion have the potential to provide complementary information of clinical value to conventional imaging for monitoring renal allografts.

Keywords: Arterial spin labeling; Arteriovenous fistula; Diffusion weighted imaging; Perfusion imaging; Transplant kidney.

Fig. 1

MR angiography (A) and CT angiography (B) with 3D reconstruction of the transplant kidney. The fistula could not be detected in either examination. At the time of the CT angiography, a double J-stent was implanted (white arrow)

Fig. 2

Digital subtraction angiography of the transplant kidney A before embolization with a red arrow pointing to the arteriovenous fistula in the upper calyx and B after embolization of the fistula. In A temporary vasospasm during angiography induced by the wire might have caused temporary vasospasm of the renal artery appearing as wall irregularities, but no manifest renal artery stenosis in this area was detected

Fig. 3

Functional MRI of the transplant kidney in the right iliac fossa: A Anatomical T2-weighted MR image depicting the renal artery (red arrow); RBF-maps in ml/min/100 g calculated from the ASL MRI before (B) and after (C) embolization; Perfusion fraction (PF) in % before (D) and after (E) embolization. Differences between measurements before and after embolization are highlighted by the white arrows pointing to the cortical perfusion deficit in the RBF map (B) and the improved cortical perfusion in the PF map in (E)

Fig. 4

Calculation of the overall renal blood flow (RBF) in ml/min/100 g from the ASL MRI and the perfusion fraction in % from the IVIM MRI before and after embolization of the arteriovenous fistula