Renal physiology: blood flow, glomerular filtration and plasma clearance

Publication date: Available online 30 March 2018 Source:Anaesthesia & Intensive Care Medicine Author(s): Clodagh Mangan, Martyn C. Stott, Raman Dhanda The kidney depends on its blood flow (20–25% cardiac output) and glomerular ultrafiltration (20% renal plasma flow) to perform it's homoeostatic and excretory functions. More than 90% of blood flow serves the cortex. Selectivity of molecular filtration in the glomerulus is related to molecular size, shape and electrostatic charge of molecules, and structure of the glomerular filtration barrier with its negatively charged glycoproteins. Ultrafiltration is determined by the balance between hydrostatic and colloid osmotic pressures (Starling forces) in the glomerular capillary and Bowman's space. It is influenced by changes in renal plasma flow, altered surface area and changes in vascular resistance afforded by afferent and efferent arterioles (mediated by sympathetic nerve activity, vasoconstrictors and vasodilators). Autoregulation of renal plasma flow minimizes changes in volume of ultrafiltration (hence, filtered load) through myogenic and tubuloglomerular feedback mechanisms. Renal clearance measurements have practical application in terms of assessing renal plasma flow and glomerular filtration rate (creatinine, inulin) along with some other measurements but all have their limitations.
Source: Anaesthesia and intensive care medicine - Category: Anesthesiology Source Type: research