[Morphometrical evaluation of the extrahepatic bile ducts in reference to their structural changes with aging]

Forty-three autopsy cases in which history of biliary diseases had not been demonstrated were submitted to histometrical evaluation of the inner diameter of common hepatic duct. In no case was there any postmortem evidence for hepatic or pancreatic diseases. The diameter D was found to be larger in aged individuals and there was a highly significant correlation between D and age. An upper rejection limit was calculated at 5% level based on the regression line of diameter against age, showing that the diameter did not exceed 4.8mm during the first two decades but the upper limit was elevated to 6.1mm and 7.5mm at 50 and 80 years respectively. It is thus necessary to take into consideration the age of the patient when we attempt to judge clinically whether or not bile ducts actually are dilated. The density in ductal wall of elastic fibers was determined by microscopic morphometry and was shown to correlate also well with both the ductal diameter and the age of patient. The dilatation of bile duct with aging appeared to be attributable to chronic tension load on its wall, which was responsible for hysteresis of mural connective tissues on one hand, and on the other, for reinforcement of ductal wall by compensatory formation of elastic fibers.