Sonographic measurements of normal gallbladder sizes in children

: Purpose. Our goal was to establish the range of sonographic measurements of normal gall-bladders in children. Methods. Six hundred ten children aged 0–16 years (male:female ratio, 1.5:1) with normal clinical and laboratory findings were included in this study. The sonographic parameters were the length, width, and calculated volume of the gallbladder, and the clinical parameters were the age, height, weight, and body surface area of the children. Statistical significance was determined through correlation and regression analyses.

2][3][4][5][6][7] Because of this lack of information, it is often difficult to determine whether a child's gallbladder is diseased.In neonates, a small gallbladder may be the result of biliary atresia, and a condition such as Kawasaki disease can lead to gallbladder enlargement accompanied by hydrops.It is therefore very important to decide whether the gallbladder size is normal.
We know of only 3 references in which the sonographic sizes of gallbladders in children are addressed, 4,8,9 and only 1 of those concerns normal gallbladders in healthy children. 8We therefore decided to measure normal gallbladders sonographically in children to establish the range of normal sizes in this population.

PATIENTS AND METHODS
This prospective study, carried out as part of a health screening program, involved 610 children aged 0-16 years (male:female ratio, 1.5:1).Written informed consent was obtained from the parents for the prospective health screening program.Physical findings concerning the upper abdomen and laboratory findings pertaining to the gallbladder were all negative, and the children were therefore considered healthy.
All subjects fasted before sonographic examination.A real-time ultrasound scanner (128XP; Acuson, Mountain View, CA) was used, with either a 3.5-or 5.0-MHz convex-array transducer.During the procedure, the subjects were usually supine, although occasionally the left lateral de-cubitus position was also used.The sonographic parameters for gallbladder size that were measured were the greatest length (L) and the greatest transverse diameter (W).It was assumed that the shape of the gallbladder was a prolate ellipsoid and that the width and anteroposterior diameter were similar.Therefore, the formula used for volume calculation was 0.52 × L × W × W (Figure 1).We also evaluated the relationships between gallbladder size and subject age, height, weight, and body surface area.
All study data were collected in the Excel program (Microsoft, Redmond, WA) and processed using the SPSS program (SPSS Inc., Chicago, IL).For gallbladder length, width, and volume, we calculated the mean ± standard deviation, median, range, and 95% confidence interval.Correlation and regression analyses were performed.A p value below 0.05 was considered statistically significant.
The gallbladder size parameters showed a significant positive correlation with age and all body parameters (p < 0.01) (Table 2).The length and volume of the gallbladder showed moderate correlations with age, height, weight, and body sur-FIGURE 1. Method of sonographic measurement of gallbladders.The gallbladder volume was measured using the prolate ellipsoid volume formula: V = 0.52 × L × W × W. A is the greatest length (L), B is the anteroposterior dimension (W) and C is the transverse width (W).B and C were assumed to be equal.face area.Correlation coefficients between the gallbladder width and body parameters were low compared with coefficients for other factors but were still significant.The greatest correlation coefficients were between gallbladder length and subject age (r ‫ס‬ 0.65; p < 0.01) and between gallbladder length and subject height (r ‫ס‬ 0.67; p < 0.01).
Regression plots also demonstrated significant linear correlations between age and gallbladder size parameters (p < 0.01) (Figure 2).Again, gallbladder width had the lowest correlation with age of the 3 size parameters.
Because of the strong correlation between gallbladder size and subject height (a simple clinical measurement), we have also presented normal gallbladder length by subject height in Table 3.

DISCUSSION
Studies of normal gallbladders in children have been few, 4,8,9 and the resulting lack of information means that decisions about whether gallbladder disease is present can be difficult.We were able to locate only 1 report, by McGahan et al, 8 in which normal pediatric gallbladder measurements are detailed.The study's sample size was small, however, totaling only 51 cases, and the clinical data were also limited.Slovis et al, 4 in a study of gallbladder hydrops in Kawasaki disease, included findings for 42 healthy children who served as the control group.And a report by Sarnaik et al 9 described the sonographic findings of some normal gallbladders in patients with sickle-cell anemia.
In the present study, we documented normal gallbladder measurements in 610 healthy children, thus establishing normal ranges that can be used in clinical settings.Since there was no pathologic proof that the gallbladders were completely normal in our study, we relied on normal

Subject Height, cm
No. Subjects Gallbladder Length, cm Mean ± SD 95% CI Median Range standard laboratory data to rule out any abnormality of the hepatobiliary system.
To establish guidelines on gallbladder size, we selected the greatest length and width and calculated the volume of the gallbladder, analyzing the relationships between these measurements and several body parameters (height, weight, and body surface area) and age.Our results demonstrated gradual but significant increases in gallbladder measurements with increases in age, height, weight, and body surface area.As in other reports, our data suggest that length is a more useful parameter than width or volume.Width, despite its significance in our study, showed a low correlation coefficient.Furthermore, an equation must be used to determine volume, making this parameter more difficult to use in clinical practice.
The relationship between gallbladder length and subject age was 1 of the strongest in our study, as most authors have reported.Our findings with regard to mean length are not greatly different from those of other authors, despite different sample sizes and the involvement of different age groups (Table 4).
It was interesting that the correlation between gallbladder length and subject height was greater than that between length and age.We therefore believe that in clinical settings, variations in gallbladder length according to subject height can also provide valuable guidance.
In conclusion, gallbladder length, width, and volume correlate significantly with subject age, height, weight, and body surface area.In particular, the length of the gallbladder is highly significantly correlated with a subject's height.

TABLE 2 Coefficients of Correlation between Body Parameters and Gallbladder Measurements*
*Data are Pearson correlation coefficients.All correlations were significant (p < 0.01).