Morphometric and biomechanical remodelling following reopening of the obstructed bile duct

Obstruction in the common bile duct results in duct dilatation, increased wall thickness and stiffening of the wall. Whether these changes are reversible after release of the obstruction has not yet been studied in detail. The aim of this study was to create a porcine model for release of bile duct obstruction and to describe biomechanical and morphometric parameters in a time-dependent design after the reopening. The bile duct of pigs was completely obstructed for one week and then reopened. Eighteen animals were allocated into four groups: unobstructed (group 1, n = 5), one week of obstruction (group 2, n = 5) and one week of obstruction followed by release of the obstruction after one week (group 3, n = 4), and four weeks (group 4, n = 4), respectively. The bile ducts were examined in vitro on the day of termination. One week of obstruction induced pronounced dilatation and wall thickening. Both the diameter and wall thickness decreased after release of the obstruction (p < 0.05) but without reaching the unobstructed level. The biomechanical properties in terms of the circumferential stress-strain relation differed between groups (p < 0.01). Groups 3 and 4 were transposed to the left of the other groups, indicating that they had the stiffest wall. The wall was stiffer in the longitudinal direction when compared to the circumferential direction in all groups (p < 0.05). The collagen amount decreased after releasing the obstruction (p < 0.01). The collagen amount correlated to the wall thickness (r > 0.9 and p < 0.001) and wall thickness-to-radius ratio (r > 0.7 and p < 0.05) in each of the two groups with release of the obstruction.