Extrahepatic bile duct length in the Singapore population

Although the length of the common bile duct is well documented, the length of extrahepatic biliary tree is less well studied, particularly in among the Asian population. The extrahepatic bile duct (BD) length is defined as the measurement from the hepatic hilum to the papilla.

This study was performed to assess the normal range of extrahepatic BD length, as defined above, in the Singapore population. This information would be useful in assisting the local endoscopy unit in procuring the different lengths of biliary stents.

Between 1.8.96 to 1.12.97, 486 cholangiograms were obtained post-ERCP, of which only 100 cholangiograms that were representative of a non-distorted BD were used for analysis. The BD length, taken from the mid-point of the confluence of the left and right hepatic ducts at the hilum to the papilla, was measured with a string placed on the cholangiogram. The true length was obtained after correction for radiological magnification.

The range of bile duct lengths followed a normal distribution curve with a mean length of 9.6 cm. The range was from 6.9 cm to 12.6 cm. With respect to the length of stents commonly deployed, the cumulative percentage of BD length less than and equal to 7-, 9-, 10- and 12-cm were 1%, 38%, 57% and 98% respectively.

From a practical point of view, this study suggests that endobiliary stent of 5 cm in length should be readily available for drainage of distal CBD strictures as 1% of our population has BD length less than 7 cm. However, as 2% of the population has BD length greater than 12 cm, 15 cm stents should be available in the endoscopy unit for drainage of hilar obstructions/strictures.