Anisotropic behaviour of human gallbladder walls

Inverse estimation of biomechanical parameters of soft tissues from non-invasive measurements has clinical significance in patient-specific modelling and disease diagnosis. In this paper, we propose a fully nonlinear approach to estimate the mechanical properties of the human gallbladder wall muscles from in vivo ultrasound images. The iteration method consists of a forward approach, in which the constitutive equation is based on a modified Hozapfel–Gasser–Ogden law initially developed for arteries. Five constitutive parameters describing the two orthogonal families of fibres and the matrix material are determined by comparing the computed displacements with medical images. The optimisation process is carried out using the MATLAB toolbox, a Python code, and the ABAQUS solver. The proposed method is validated with published artery data and subsequently applied to ten human gallbladder samples. Results show that the human gallbladder wall is anisotropic during the passive refilling phase, and that the peak stress is 1.6 times greater than that calculated using linear mechanics. This discrepancy arises because the wall thickness reduces by 1.6 times during the deformation, which is not predicted by conventional linear elasticity. If the change of wall thickness is accounted for, then the linear model can used to predict the gallbladder stress and its correlation with pain. This work provides further understanding of the nonlinear characteristics of human gallbladder

Quality of life and psychological and gastrointestinal symptoms after cholecystectomy : a population-based cohort study

OBJECTIVE: The study aims to examine gastrointestinal symptoms, quality of life and the risk of psychological symptoms after cholecystectomy. DESIGN: This is a prospective population-based cohort study based on the Nord-Trondelag Health Study (HUNT) Norway. HUNT is a repeated health survey of the county population and includes a wide range of health-related items. In the present study, all 3 HUNT surveys were included, performed between 1984 and 2008. Selected items were scores on quality of life, the Hospital Anxiety and Depression Scale (HADS) and selected gastrointestinal symptoms. Participants who underwent cholecystectomy for gallstone disease between 1 January 1990 and until 1 year before attending HUNT3 were compared with the remaining non-operated cohort. Associations between cholecystectomy and the postoperative scores and symptoms were assessed by multivariable regression models. RESULTS: Participants in HUNT1, HUNT2 and HUNT3 were 77 212 (89.4% of those invited), 65 237 (69.5%) and 50 807 (54.1%), respectively. In the study period, 931 participants were operated with cholecystectomy. Cholecystectomy was associated with an increased risk of diarrhoea and stomach pain postoperatively. In addition, cholecystectomy was associated with an increased risk of nausea postoperatively in men. We found no associations between cholecystectomy and quality of life, symptoms of anxiety and depression, constipation, heartburn, or acid regurgitation following surgery. CONCLUSIONS: In this large population-based cohort study, cholecystectomy was associated with postoperative diarrhoea and stomach pain. Cholecystectomy for gallstone colic was associated with nausea in men. There were no associations between quality of life, symptoms of anxiety and depression, constipation, heartburn, or acid regurgitation.Swedish Research CouncilPublishe