**5.2 Radiocontrast-mediated changes in renal blood supply**

Renal blood flow and intrarenal microcirculation are markedly altered by contrast medium (CM) [53]. The extent and distribution of renal hemodynamic changes depends on the species investigated as well as on the type, volume, and rate of contrast administration. Moreover, renal hemodynamic effects of CM gravely depend on the hydration state and on additional predisposing factors that may have an effect on the renal circulation and the tone of the renal vasculature, such as chronic renal disease, diabetes mellitus, senility, and inflammation. In an early study in dogs subjected to a high-osmolar CM, total renal blood flow was transiently enhanced for 5–15 min, followed by a decline by 25% below baseline, reaching beyond a couple of hours [54]. In healthy humans, renal blood flow fell 8% over 30 min after the intravenous administration of conventional doses of CM [53]. On the contrary, in patients with chronic kidney disease undergoing coronary angiography, a transient short augmentation of renal blood flow was followed by a dramatic 40% decline, lasting for more than 3 h [54].
