THE STONE FORMAION IN GALLBLADDER

– THE ROLE OF FLUID MECHANICS?

Gallstones and other biliary diseases affect about 10% of the adult population of the UK. Up to 60,000 operations to remove the gallbladder are being performed in the UK each year, at a cost of about £40 million to the NHS. Understanding of the pathogenesis of gallstone disease and pain production mechanism is poorly understood, and complications of gallstones i.e. acute pancreatitis and obstructive jaundice may be fatal.

The biliary system consists of pliable tubes and various valves into which bile and pancreatic juices are secreted under pressure. The gallbladder receives dilute bile from the liver, stores and concentrates it during the inter-digestive period and evacuates the more viscous gallbladder bile in response to a meal-stimulated contraction. The bi-directional flow is controlled by the cystic duct, commonly known the Heister valve or the spiral valve. Extensive clinical and in vitro studies at the Sheffield Gallstone Centre have strongly suggested that the critical unknown in the normal and pathophysiology of the biliary system is in the filling and evacuation of the gallbladder and the flow through the cystic duct. Some of the pressing questions which need to be addressed are:

· What is the role of fluid mechanics in the formation of the gallstones?

· How does cystic duct control the bi-directional flow and what is the role of the sphincter of Oddi?

· How bile may flow up the pancreatic duct against the pressure gradient to produce pancreatitis?

· What is the effect of drugs on the mechanical behaviour of the system?

These questions can best be resolved by obtaining clinical and in vitro data and to study them in bench model experiments, augmented by computational fluid dynamic modelling studies. The contraction/expansion of the gallbladder poses a strongly coupled fluid-structure interaction problems. The combined clinical and physical/computational investigations of possibly non-Newtonian fluids (bile) flow present a challenging interdisciplinary research problem.

Collaborators: Dr. N. Bird, The Hallamshire Hospital, University of Sheffield

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