Pediatric portal venous dimensions: a computed tomography-based normative study utilizing multiplanar reformation

Paediatric portal vein reference values are derived almost exclusively from ultrasound, which systematically yields smaller measurements than CT. CT-specific normative data for children are limited to a single study that did not include multiplanar reformation (MPR) measurements, splenic vein data, or comprehensive anthropometric analysis.

To establish CT-based reference values for the portal venous system in children and adolescents, including both axial and MPR measurements of the main portal vein, and to characterize the systematic discrepancy between the two measurement methods.

In this single-centre retrospective study, 1,101 children aged 0-17 years who underwent contrast-enhanced abdominal CT between January 2018 and April 2026 were included after applying strict exclusion criteria. Main portal vein (axial and MPR), right portal vein, left portal vein, and splenic vein diameters were measured independently by two radiologists. Age- and body surface area-stratified reference values were generated using locally weighted scatterplot smoothing (LOESS).

MPR measurements exceeded axial measurements in all 1,101 subjects (mean difference 1.2±0.9 mm; proportional bias r=0.523, P<0.001). Age showed the strongest correlation with main portal vein diameter (ρ=0.894). Sex-based differences emerged exclusively in subjects aged ≥13 years (all P≤0.006). The splenic-to-main portal vein ratio remained relatively stable across the paediatric age spectrum (coefficient of variation 8.2%). Interobserver agreement was excellent for all parameters (ICC, 0.986-0.993).

CT-based portal venous reference values in children differ substantially from ultrasound-derived reference values. MPR measurements systematically exceed axial measurements, particularly in adolescents. Because MPR permits measurement perpendicular to the vessel long axis, use MPR-specific reference values when MPR-based measurements are employed.