Urine concentrating mechanism modelling in rat kidney inner medulla

Physicians use charts that are prepared by experiments on animals or humans to prescribe drug dosage for patients. This method requires some precious amount of time by the Ministry of Health to approve new drugs to be used in healthcare centers. Three-dimensional modeling of the inner medulla by considering the known physiological features help us to predict the distribution of a drug or any minerals in the kidney. In this study we present modeling of the important species distribution including Na
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and urea in the rat inner medulla that influence the urine concentrating mechanism. We use a C++ code to develop the inner medulla geometry based on physiological data to better capture the concentrating mechanism. Features such as tubules variable diameters, pre-bend length and tubules' lateral distance relations have been considered in generating the geometry. Next, a CFD study is done to simulate the concentration of urea and Na
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along the corticomedullary axis using boundary conditions from the previous study on outer medulla for the inner medulla base. Results show a dramatic increase in concentration of the collecting ducts near the tip of the papilla. Concentration of urea and Na
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in the interstitium along the corticomedullary axis at different segments demonstrate an analogous pattern to the three-dimensional position of the different types of tubules with respect to each other that indicates the significance of the three-dimensional modeling in this simulation.