Disorders of Glomerular Filtration

In the first edition of this volume, this chapter dealing with disorders of glomerular filtration described, by necessity, few specific mechanisms of altered glomerular ultrafiltration, because the stage of development of this field of investigation was in a rather early phase of data accumulation. Since that time, there has been a considerable acceleration in the rate of accumulation of knowledge in this area. Therefore, in this second edition, we will diminish our prior emphasis on methodology and discussion of the modeling predictions of the relative impacts of the four individual determinants of glomerular ultrafiltration: (1) nephron plasma flow (RPF); (2) systemic oncotic pressure (πA); (3) the glomerular capillary hydrostatic pressure gradient (ΔP); and (4) the glomerular ultrafiltration coefficient (LpA). We refer the reader to the first edition of this text for this more methodologic and theoretical discussion. We will now focus upon what is currently known regarding the specific mechanisms contributing to the regulation of glomerular ultrafiltration in a variety of physiologic and pathophysiologic conditions. Because of the increasing complexity of the regulatory processes, the descriptions of these mechanisms will be classified by physiologic conditions rather than focusing specifically on the effects of changes in the respective determinants of glomerular ultrafiltration.