Are Signals from Implantable Doppler Probes Always Accurate for Prediction of Blood Flow in Kidney Transplant?

Vascular anastomotic occlusion has a catastrophic outcome in kidney transplant. The implantable Doppler probe is a blood-flow monitoring device that provides real-time information and direct assessment of anastomotic patency. We present the case of a complex kidney transplant recipient who was postoperatively monitored with an implantable Doppler probe attached to the renal artery. The patient showed clinical deterioration despite a continuous trace of Doppler signals. An urgent color duplex scan confirmed renal vein thrombosis. Interestingly,the Doppler signals persisted during the surgical exploration, which revealed a grossly discolored and congested graft with renal vein thrombosis. The persistent Doppler signals were caused by the back-and-forth blood flow in the renal artery due to the blood pressure shifts during the cardiac cycle against the high intrarenal resistance of the thrombosed graft. Therefore, the signals of implantable Doppler probes should be interpreted alongside the traditional clinical assessment techniques to ensure safe and effective postoperative monitoring. This information will inform the clinical practice in kidney transplant surgery.