Algebraic Formula Predicting the Fraction of Absorbed Fluid Transported By Mesenteric Lymphatic Vessels

Abstract

When nutrients are absorbed into the interstitial space from the intestinal lumen, they can be transported either by the intestinal capillaries to the portal circulation or by mesenteric lymphatics to the cysterna chyli. Several perturbations can alter the fraction of fluid that is transported by the mesenteric lymphatics, including nutrients present in the intestinal lumen, and microvascular and cysterna chyli hydrostatic pressures. Experimental approaches employed to elucidate the mechanisms governing the relative flow through these two parallel pathways are limited, because critical parameters are difficult to measure and cannot be controlled independently. Conventional mathematical modeling approaches are also limited, because the numerical solution of of the systems of equations are sensitive to assumed parameter values and must employ advanced computational techniques. Therefore, the purpose of the present work was to develop a general algebraic formula that predicts the fraction of fluid that is transported by the mesenteric lymphatic vessels. The basic framework was developed by equating the fluid flow into the intestinal interstitial compartment from the lumen and fluid removed by mesenteric lymph flow and microvascular absorption. Transport of fluid between the interstitium and the capillaries was characterized by the Starling‐Landis equation. Lymph flow from the intestinal interstitium to the cysterna chyli was assumed to be a linear function of interstitial and cysterna chyli hydrostatic pressures. Nutrients were assumed to be actively transported from the intestinal lumen, and water was assumed to be transported iso‐osmotically as characterized by the Starling‐Landis equation. The system of equations were solved algebraically to yield a formula for the fraction of fluid transported by the mesenteric lymphatic vessels. This simple model reproduces measured values of fluid flows, as well as the preferential transport of fluid by mesenteric lymphatic vessels when lipids are absorbed. Not only does it predict how fluid transport is affected by changes in parameters characterizing microvascular and lymphatic function, it provides a novel means to estimate critical parameter values from measured fluid flow.