The Gomez equations and renal hemodynamic function in kidney disease research

Abstract

Diabetic kidney disease (DKD) remains the leading cause of end-stage renal disease. A major challenge in preventing DKD is the difficulty in identifying high-risk patients at a preclinical stage. Existing methods that are used to assess renal function, including albuminuria and eGFR, do not give detailed insight into the location of the renal hemodynamic effects of pharmacological agents at the segmental level. To gain additional information about the intrarenal circulation in vivo in humans, equations were developed by Gomez et al. in the 1950s. These equations used measurements of glomerular filtration rate, renal blood flow, effective renal plasma flow, renal vascular resistance, hematocrit, and serum protein to calculate afferent and efferent arteriolar resistances, glomerular hydrostatic pressure, and filtration pressure. The Gomez equations are, however, indirect and based on physiological assumptions derived from animal models, which may not hold true in human pathophysiology, including the assumption of a normal gross filtration coefficient and not considering changes in intratubular pressure that may affect the pressure gradient across the glomerular capillaries. Nevertheless, the equations have the potential to improve researchers' ability to identify early preclinical changes in renal hemodynamic function in patients with a variety of conditions, including DKD, thereby offering potential in mechanistic human research studies. In this review, we focus on the application of Gomez' equations and summarize the potential and limitations of these techniques in DKD research. We also summarize illustrative data derived from Gomez' equations in patients with type 1 and type 2 diabetes and hypertension.