Determination of the umbilicus position in Japanese children.

[BACKGROUND] Although there have been many reports concerning the normal position of the umbilicus, the measurements were performed from the surface of the body in all cases. We examined computed tomography (CT) images to determine the accurate position of the umbilicus in children.

[METHODS] We retrospectively examined the CT data of 120 Japanese children (60 boys, 60 girls). The angle between both iliac crests to the umbilicus (IU angle), the angle between both anterior superior iliac spines and the umbilicus (AU angle), and the ratio of the length from the xiphoid process to the umbilicus and length from the umbilicus to the pubic symphysis were measured.

[RESULTS] The mean AU angle was 33.7° ± 5.1°, showing the least data variations. A significant difference was noted in the AU angle between boys and girls (32.7° ± 4.6° and 34.6° ± 5.4° respectively; p = 0.04). When we defined the position of the umbilicus as an AU angle of 33° in boys and 35° in girls, 115 children (95.8%) fell within ±10°.

[CONCLUSIONS] The AU angle is the preferable predictor of the umbilicus position in children.