<prompt> The most important sign of significance of renal artery stenosis on an angiogram isA percentage diameter stenosis 70Presence of collateralsA systolic pressure gradient 20 mm Hg across the lesionPoststenotic dilatation of the renal artery  <response>: The presence of arterial collaterals indicates that renal artery stenosis is hemodynamically significant. The diameter of stenotic segment may also give an indication of hemodynamic significance, but is only reliable if the stenosis is either very severe or minimal . 