Ultrasound measurement of corporeal (penile) length in newborns

In the initial clinical examination of a child with ambiguous genitalia an accurate measurement of the corporeal length is needed. Most often the corporeal length is measured with a ruler from the symphysis pubis to the tip of the glans of a stretched penis. More recently, ultrasound has been successfully used to measure corporeal length. This study aimed to (i) establish normal values for corporeal length in normal male newborns using ultrasound measurement, (ii) compare these measurements to stretched corporeal measurements, (iii) compare the corporeal length of newborns of different races, and (iv) determine the relationship between corporeal length and birth weight, birth length and head circumference. This was a prospective study of 141 newborns. Ultrasound imaging was done in an oblique parasagittal plane such that the corpus could be included in a single image and measured, Stretched corporeal length was measured with the penis stretched alongside a wooden spatula and the length from the pubic bone to the tip of the glans was marked on the spatula and measured. By ultrasound measurement the mean corporeal length of the normal newborn was 3.18 +/- 0.56cm. There was no significant difference in the mean corporeal length when determined by ultrasound and by stretched corporeal measurement. There was no significant difference in the mean corporeal length of the different races when the length was determined by either ultrasound or stretched corporeal measurement. There was a positive correlation between ultrasound length and birth weight and birth length. However, there was no correlation between ultrasound length and head circumference. There was no significant correlation between the stretched length and either birth weight, birth length or head circumference.