On the mechanical behavior of the human biliary system

Abstract

This paper reviews the progress made in understanding the mechanical behaviour of the biliary system. Gallstones and diseases of the biliary tract affect more than 10% of the adult population. The complications of gallstones, i.e. acute pancreatitis and obstructive jandice, can be lethal, and patients with acalculous gallbladder pain often pose diagnostic difficulties and undergo repeated ultrasound scans and oral cholecystograms. Moreover, surgery to remove the gallbladder in these patients, in an attempt to relieve the symptoms, gives variable results. Extensive research has been carried out to understand the physiological and pathological functions of the biliary system, but the mechanism of the pathogenesis of gallstones and pain production still remain poorly understood. It is believed that the mechanical factors play an essential role in the mechanisms of the gallstone formation and biliary diseases. However, despite the extensive literature in clinical studies, only limited work has been carried out to study the biliary system from the mechanical point of view. In this paper, we discuss the state of art knowledge of the fluid dynamics of bile flow in the biliary tract, the solid mechanics of the gallbladder and bile ducts, recent mathematical and numerical modelling of the system, and finally the future challenges in the area.

Non-Newtonian Bile Flow in Elastic Cystic Duct: One- and Three-Dimensional Modeling

“…Incomplete drainage of the gallbladder may occur when the resistance to flow is too high; this requires further study. Preliminary work by us 29,31 suggests a correlation between pain and mechanical stresses of the biliary system, and this paper indicates that non-Newtonian effects will contribute to these stresses.…”

Anisotropic behaviour of human gallbladder walls

“…The nonlinear modelling itself also still faces the same challenges as the linear model, namely, how to estimate the intraluminal pressure non-invasively, and how to evaluate the effects of patient specific GB geometries. In view of this, it seems plausible to continue to use the linear model as a clinical tool to provide a quick first evaluation of the stress trend, as has been done successfully in the previous studies (Luo et al 2007;Li et al 2011a;Li et al 2011b), but bear in mind that the stress within the GB wall may be underestimated by approximately a factor of approximately 1.6, which reflects the ratio of the wall thickness reduction. However, for clinical cases that require careful attention and involve critical decision making, finite strain nonlinear models must used to provide more accurate stress evaluations.…”

Mandatory and optional function tests for biliary disorders

“…Considering the biliary tract as a pump-pipe system, the gallbladder provides the driving force with the flow rate of bile further depending on resistance in the duct system and the pressure gradient between the gallbladder and the distal part of the common bile duct [10]. Both supersaturation of the bile with cholesterol or bilirubin and bile stasis as a consequence of gallbladder hypomotility accelerate stone formation.…”