Do renal blood flow changes impact glomerular filtration rate?

Abstract

The glomerular filtration rate (GFR) and the renal blood flow (RBF) correspond to the filtered volume by the kidneys and the blood volume delivered by the renal arteries per unit of time, respectively. The relationship between GFR and RBF is complex. A better understanding of renal physiology is needed to delineate the impact of modifications in renal hemodynamics on GFR. In each glomerulus, ultrafiltration is determined by the difference between the hydrostatic pressures in the glomerular capillary and the Bowman’s space, the coefficient of ultrafiltration (K_f) and the oncotic pressure in the afferent arteriole. The relationship between GFR and RBF depends on the renal autoregulation, allowing the maintenance of a constant GFR over a large range of perfusion pressures. In animals, at the early stages of sepsis, GFR is correlated with cardiac output. In contrast, at later stages, a decline in GFR is observed in animals and humans along with the development of renal vascular damage. After renal vascular damage has occurred, the reduction in GFR is much greater in comparison to the reduction in RBF. The complexity of the mechanisms involved in the relationship between GFR and RBF and the progression in this relationship over time likely explains the repeated failures of hemodynamic interventions in rescuing renal function after end-organ insult.