Renal blood flow plays an important role in the kidneys' function of filtration, reabsorption, and urine secretion at nephrons. Plenty of anatomical and numerical clarified that renal blood flow distribution in space and time is related with complex vessel structures that forms a network flow system. The purpose of this study is to understand how renal vessel structures affects the blood flow from bio-fluid-mechanics viewpoints, using a numerical model of the blood-urine flow system.

An electric circuit model of blood flow in the renal vessel network was constructed to involve large vessels, small vessels, capillaries and nephrons, as well as proximal and distal convoluted tubules and ureters to the urinary bladder for the urinary flow. The blood and urinary flows were coupled by the glomerular ultrafiltration and tubular reabsorption, placing flow paths with suitable flow resistance and extra pressure difference. Referring to published micro-computer tomography data and complex branching characteristics, a bifurcating structure of small vessels was assumed. Fluid analysis with the electric circuit model was carried out to simulate flow rate and pressure.

Simulated flow rates and pressure distribution in blood vessels, glomerular filtration rate, renal reabsorption rate, and urinary excretion rate were consistent with those of experimental measurement. This demonstrated that the capability of the proposed model to express normal renal circulation. A blood vessel structure, such as characterized by the vessel number, affected blood pressure. This might indicate that a certain vascular structure is necessary for maintaining a physiological range of glomerulus pressure (Fig. 1).

Keywords: Computational biomechanics, Kidney, Renal vessel, Blood flow