Exploring the Mechanisms of Human Gallbladder Pain

Gallstone and other diseases of the biliary tract affect more than 10% of the adult population of the UK. Up to 60,000 operations to remove the gallbladder are performed in the UK each year, at a cost of approximately 40 million to the NHS. However, due to our lack of understanding of the pain mechanism, surgery is often conducted without any guarantee of relieving the symptoms. The purpose of this project is to explore the pain mechanism using a mechanical model. When gallbladder contracts during emptying, not only the intra-luminal pressure rises, but the size and shape of the gallbladder also change depending on the downstream flow condition. Consequently, the various stress distributions in the gallbladder muscle wall also change. We believe that it is the total stresses in the gallbladder, not the pressure or volume change, that play the key role in the gallbladder pain. We aim to establish this new concept by carrying out a non-linear stress analysis of the gallbladder models, including both the passive and the active stresses. This model will be tested against controlled clinical experiments for various subjects. The work proposed here is significant for understanding the gallbladder pain mechanism since this is the first approach using mechanical modelling of the human biliary system. Although it is generally believed that the pain receptors are likely to be mechano-sensitive, the precise link between these remains unclear. If the new concept can be confirmed in this project, it will provide a much clearer picture of the problem, and help with more efficient surgical diagnosis.