Visibility and Size of the Pancreatic Duct and Common Bile Duct on Routine 2D MRI Sequences in Children Without Pancreaticobiliary Disease.

Pancreatic duct (PD) or common bile duct (CBD) dilatation can indicate ductal pathology, but limited data describe normal pediatric duct measurements on routine 2D MRI sequences. The purpose of this study was to characterize the visibility and diameter of the PD and CBD on 2D MR images in children without pancreaticobiliary disease. This retrospective study included patients who underwent abdominal MRI using a rapid protocol (composed of noncontrast axial and coronal 2D SSFSE sequences) to assess for suspected appendicitis or ovarian torsion in the emergency department setting between January 23, 2023, and September 13, 2023, and excluded patients with a pancreatic or hepatobiliary abnormality on MRI or laboratory assessment. Four pediatric radiologists independently reviewed examinations. Reviewers recorded PD visibility in each of four segments (i.e., head, neck, body, and tail) and CBD visibility, and reviewers measured PD diameter in each segment and maximal CBD diameter. Duct measurements by age were characterized by linear regression analyses. The study included 177 patients (112 female patients, 65 male patients; mean age, 12.3 ± 3.4 [SD] years [age range, 5.1-17.7 years]). The observers reported PD visibility in the head in 35.6-94.9% of patients, neck in 18.6-72.3%, body in 22.6-89.8%, and tail in 7.3-26.0% and reported PD visibility in all four segments in 6.2-22.6% of patients. Maximum PD diameter in any segment, as a mean across observers, was 1.8 mm (range across observers, 0.7-3.5 mm). The expected maximal PD diameter in any segment, in terms of the 5th and 95th percentile values of observers' mean measurements, was 1.4-2.3 mm; the prediction interval's upper limit increased from age 5 to age 17 from 2.1 to 2.5 mm. All observers reported CBD visibility in all patients. The mean CBD diameter across observers was 3.1 mm (range across observers, 2.9-3.4 mm). The expected CBD diameter, in terms of the 5th and 95th percentile values of observers' mean measurements, was 2.3-4.9 mm; the prediction interval's upper limit increased from age 5 to age 17 from 3.9 to 5.0 mm. We report expected upper limits for PD and CBD measurements on 2D MR images in children without evidence of pancreaticobiliary disease. These findings may aid radiologists' identification of pancreaticobiliary duct abnormalities on routine abdominal MRI examinations.