Determining the normal aorta size in children

To establish effective aorta diameter standards at multiple levels of the thoracic aorta, abdominal aorta, and common iliac arteries by using computed tomographic (CT) data in healthy children (infants, children, adolescents) through young adults (hereafter referred to collectively as "children") of a wide range of sizes so that z scores may be calculated.

This retrospective study was approved by the institutional review board. The effective diameter, the average of aortic anteroposterior and lateral diameters, was independently measured at multiple levels of the aorta and common iliac arteries by two radiologists using 1-mm-collimation double-oblique reconstructions. Ordinary least squares regression methods were used to investigate models with various functional forms that related effective diameters at each level to patient body surface area (BSA) and sex. The best model was selected by using R(2), and formulas for deriving the expected diameter and estimates of the mean squared error (MSE) were generated.

Results from 88 thoracic and 110 abdominal contrast material-enhanced CT examinations were analyzed in children without known cardiovascular disease who ranged in age from 0 to 20 years (mean, 9.9 years; standard deviation, 5.7), with BSA ranging from 0.19 to 2.52 m(2). Excellent interrater reliability was present (correlation coefficients ranged from 0.95 to 0.98). The best model was a polynomial regression model of the natural log transformation of the effective diameter that included linear, quadratic, and cubic BSA terms and a sex main effect as independent variables. The z scores were calculated by using the observed and expected effective diameters and the MSE.

The range of normal effective diameters of the aorta at multiple levels and the common iliac arteries was determined for children of different sizes and both sexes. Measurements outside of the normal ranges are consistent with aneurysm or hypoplasia.