Postmicturition residual bladder volumes in healthy babies.

Thirty eight assessments of postmicturition residual volume were undertaken in 34 babies of various gestational and postnatal ages using abdominal ultrasonography. Twenty one (54%) babies had no detectable residual bladder volume. In all cases manual expression of the bladder failed to eliminate the residual volume. The formula widely used in the estimation of fetal bladder size and urine output is not applicable in the newborn infant.