Functional assessment of the circulation of the single kidney

Functional alterations in the renal circulation that can contribute to abno rmal renal perfusion have been demonstrated in various models of renal inju ry. To detect impairments in renal vascular function, renal flow reserve ca n be determined by repeated measurements of renal blood flow (RBF) during p harmacological challenge with short-acting vasodilators that should increas e RBF in kidneys that are not severely damaged structurally. Among the inva sive techniques for such measurements, the most readily available is probab ly the intravascular Doppler, which can be employed during renal angiograph y for rapid evaluation of changes in RBF during intrarenal injections of va soactive substances. High-resolution tomographic imaging techniques, like e lectron-beam x-ray computed tomography, further offer the potential for non invasive measurements of renal parenchymal perfusion and function, in assoc iation with either intrarenal or systemic injections of vasoactive substanc es. Acetylcholine is a potent short-acting renal vasodilator that can be us eful to assess the response of the renal microcirculation, define renal flo w reserve, and examine the endothelium-dependent responses of RBF. Such ass essments of the function of the renal circulation can assist in evaluation of patients with systemic or renal disease for early detection and monitori ng of renovascular injury.