Detection of transplant renal artery stenosis in the early postoperative period with analysis of parenchymal perfusion with ultrasound contrast agent

Background: Transplant renal artery stenosis (TRAS) is a serious vascular complication due to non-specific clinical manifestations, causing serious diagnostic difficulties. Contrast-enhanced ultrasound (CE-US) can complement standard sonographic examination in evaluation of TRAS. Material/Methods: Standard ultrasound B presentation, extended with color Doppler assessment of the flow spectrum and CE-US, was carried out in the early postoperative period in a group of 180 patients who underwent kidney transplantation. In CE-US analysis, the maximum contrast agent perfusion to the cortex and renal pyramids was evaluated. In 15 patients with sonographically diagnosed TRAS, magnetic resonance angiography and computer tomography angiography were performed to confirm the diagnosis. Results: In patients with TRAS, significantly longer time of contrast agent (CE) inflow was observed in comparison to patients without perfusion disturbances (3.47 s vs. 1.5 s, p<0.000 for cortex; 6.01 vs. 2.09 s for pyramids, p<0.000). The rate of CE inflow was strongly positively correlated with severity of stenosis assessed on the basis of CTA/MRA examination (R=0.97 for cortex and 0.9 for pyramids; p<0.001). Six months after kidney transplantation, patients with a history of TRAS had significantly higher serum creatinine level than recipients with normal renal artery blood flow (1.76 mg/dL vs. 1.53 mg/dl, p<0.02). Estimated GFR was decreased to 35.9 ml/min vs. 46.5 ml/min, respectively (p<0.05). Conclusions: Contrast-enhanced ultrasound allows for quick and non-invasive assessment of parenchymal kidney graft perfusion. It enables confirmation of TRAS diagnosis in the early postoperative period and helps assess the degree of stenosis.