The Doppler ultrasound image shows an elevated peak systolic velocity (PSV) of 637 cm/s, an elevated end-diastolic velocity (EDV) of 312 cm/s, and a low resistive index (RI) of 0.51 at the arterial anastomosis of a renal transplant. These findings are characteristic of significant renal artery stenosis (RAS) at the transplant vascular anastomosis.

Key sonographic features of renal artery stenosis:

Peak systolic velocity (PSV) > 250–300 cm/s at the stenotic segment (this case: 637 cm/s)

Post-stenotic turbulence with spectral broadening

Low resistive index (RI < 0.56 suggests downstream vasodilation)

Elevated acceleration time (AT > 0.07 sec), and reduced acceleration slope

Aliasing on color Doppler due to high velocity

In this image, the marked increase in velocity with spectral aliasing and low RI is diagnostic of transplant renal artery stenosis — the most common vascular complication post-transplant, typically occurring at the site of surgical anastomosis.

Differentiation from other options:

A. Iliac arteritis: A rare condition, not typically presenting with these Doppler changes.

C. Renal vein thrombosis: Would show reversed or absent diastolic flow, not elevated systolic velocities.

D. Arteriovenous malformation (AVM): Produces a high-velocity, low-resistance waveform but is associated with color bruit, aliasing, and pulsatile venous waveforms — not evident here.