Renal hemodynamics: Theory and practical tips

The angiographic assessment of renal artery stenosis (RAS) is often difficult and not reliable. A hyperemic systolic pressure gradient (HSPG) >20 mm Hg provides the highest concordance rate of 100% with an intravascular ultrasound (IVUS) minimal lumen cross sectional area <8.6 mm(2) to predict the severity of RAS. We present 4 cases in whom the role of HSPG and IVUS compared with angiography for the assessment of the severity of RAS is discussed.