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Abstract
We present a mathematical model of blood and interstitial flow in the liver. The liver is treated as a lattice of hexagonal ‘classic’ lobules, which are assumed to be long enough that end effects may be neglected and a two-dimensional problem considered. Since sinusoids and lymphatic vessels are numerous and small compared to the lobule, we use a homogenized approach, describing the sinusoidal and interstitial spaces as porous media. We model plasma filtration from sinusoids to the interstitium, lymph uptake by lymphatic ducts, and lymph outflow from the liver surface. Our results show that the effect of the liver surface only penetrates a depth of a few lobules’ thickness into the tissue. Thus, we separately consider a single lobule lying sufficiently far from all external boundaries that we may regard it as being in an infinite lattice, and also a model of the region near the liver surface. The model predicts that slightly more lymph is produced by interstitial fluid flowing through the liver surface than that taken up by the lymphatic vessels in the liver and that the non-peritonealized region of the surface of the liver results in the total lymph production (uptake by lymphatics plus fluid crossing surface) being about 5 % more than if the entire surface were covered by the Glisson–peritoneal membrane. Estimates of lymph outflow through the surface of the liver are in good agreement with experimental data. We also study the effect of non-physiological values of the controlling parameters, particularly focusing on the conditions of portal hypertension and ascites. To our knowledge, this is the first attempt to model lymph production in the liver. The model provides clinically relevant information about lymph outflow pathways and predicts the systemic response to pathological variations.
Highlights
The liver is one of the vital organs in the human body, and it plays a fundamental role in numerous functions, including protein synthesis, metabolism, bile secretion, and detoxification
The liver has a circulatory system specific to its function. It is supplied by two major blood vessels: the hepatic artery, which contains fully oxygenated blood, and the hepatic portal vein, which contains partially deoxygenated blood that is rich in nutrients, since it originates from the intestines
We develop a mathematical model of blood and interstitial fluid flow in a lobular model of the liver, in order to estimate the rate of uptake of lymph and the flux of fluid across the surface of the liver
Summary
The liver is one of the vital organs in the human body, and it plays a fundamental role in numerous functions, including protein synthesis, metabolism, bile secretion, and detoxification. Rani et al (2006) developed a computational fluid dynamics model of flow along a terminal portal vein, hepatic artery, and two sinusoids with fenestrations. They used a non-Newtonian shear-thinning model for the blood rheology. Debbaut et al (2012a) used a cast of a liver, combined with a computational fluid mechanical simulation, to find the effective permeability of the sinusoids in different directions through the tissue, while Debbaut et al (2012b) employed these data to develop a three-dimensional lobular model, which they used to investigate the role of the vascular septa. We prescribe the blood pressure at the portal tracts and central veins, and we assume that blood vessels do not cross the vascular septa from one lobule to its neighbor
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