P11: Mechanical Properties of the Common Bile Duct: Insights into Benign Biliary Structure Pathophysiology

Abstract

Benign biliary strictures (BBS) that develop in the common bile duct (CBD) are often a result of postoperative or inflammatory processes. For instance, one-third of patients who undergo procedures such as cholecystectomy or liver transplants can develop surgery-related BBS. Current treatments for BBS are plagued by difficulties, complications, and failures, which result in high costs and risks associated with reinterventions. The failures may be due to a lack of knowledge about the structure of the CBD and the use of devices that are not designed for this specific application. This study aims to determine the mechanical properties of the CBD to better understand the pathophysiology of BBS, calibrate computational models, and the future evaluation of new treatment methods. Geometrical measurements and evaluations of the bile ducts (CBD, sphincter of Oddi, cystic, and common hepatic ducts) and the gallbladder were carried out on 31 adult pigs obtained from a local slaughterhouse. Pressurized diameter measurements were recorded at healthy and pathological pressures, and burst tests were performed on CBD sections (n=3). Longitudinal (lon, n=16) and circumferential (circ, n=25) tensile strength tests were performed on CBD sections at a rate of 50 mm/min until rupture, yielding the modulus of elasticity (E), ultimate strength, and fracture strengths. A creep test was performed in a bath at -4°C, with a weight of 3 g applied for 28 days. The test involved a 90° turn at day 14, with deformation monitored for 7 days without load (n=3). A high degree of variability was reported in bile duct size in terms of length (84.1 ± 17.5 mm) and relaxed diameter (6.2 ± 1.9 mm). The modulus of elasticity associated with elastin (0.111 ± 0.111 MPa) and collagen (4.744 ± 2.193 MPa) exceeded the circumferential values (0.019 ± 0.017 MPa and 2.850 ± 1.585 MPa, respectively). Lower results for the modulus of elasticity and higher dilation after the creep tests were observed in the proximal zone of the CBD near the duodenum (day 14: 41%, day 28: 43%, day 35: 67%), indicating lower stiffness. Additionally, all regions of the CBD retained most of their deformation even after 7 days in the absence of load. The data reported in this study provides valuable information on how the technique and treatment times can be improved in cases of BBS.