Normograms for the Extrahepatic Bile Duct Diameter in Children

The normal diameter of the extrahepatic bile duct (EHD) in children has been poorly studied. Prior studies have enrolled small subject numbers, have studied only specific pediatric age groups, or have potential bias due to loosely defined exclusion criteria. We sought to establish parameters for the normal diameter of the EHD in children from birth to late adolescence, including premature infants.

A 12½-month institutional review board-approved, Health Insurance Portability and Accountability Act-compliant, retrospective chart review of all transabdominal ultrasounds performed on children (younger than 18 years) was conducted at a single pediatric tertiary referral center. Exclusion criteria included a past medical history of any pancreaticobiliary or hepatology disorder. New abnormal findings related to the liver, biliary system, or pancreas were also excluded. Recorded EHD measurements from review of the radiology reports were compiled. Estimated mean and 95% prediction intervals of EHD were calculated and reported for 6 nonoverlapping pediatric age groups.

A total of 1016 ultrasounds on unique patients were included within the study. Estimated mean values and calculated 95% prediction intervals (in parentheses) for the diameter of the EHD were prematurity, 0.7 (0.3-1.7) mm; 0 to 2 months, 1.0 (0.4-2.3) mm; 3 to 11 months, 1.2 (0.5-2.9) mm; 1 to 4 years, 1.4 (0.6-3.3) mm; 5 to 12 years, 1.9 (0.8-4.3) mm; 13 to 17 years, 2.3 (1.0-5.2) mm.

Our derived data of normal predicted parameters of the EHD diameter in children of all age groups will help guide clinicians in identifying those patients outside the norm that may benefit from additional testing.