Background. The number of reports on the sonomorphology of the urachus
or urachal remnants in neonates and the pattern of involution is limi
ted. Objective. To determine whether a sonographically visible urachus
in the first months of life is a pathologic condition and whether pos
tnatal involution can be demonstrated by ultrasound. Materials and met
hods. A total of 102 asymptomatic infants (premature and term newborns
) were examined with a high-resolution 7.5-MHz linear transducer betwe
en 0 and 60 days of age. In 70 infants, a second examination followed
3-5 months later. Results. In all infants, the urachus could be identi
fied on the first examination. Different morphological types were diff
erentiated. There was no difference between premature and term newborn
s in the morphology of the urachus. Spontaneous involution of the urac
hus was observed in all infants receiving a second examination, and th
ey most often showed a fusiform urachal remnant at the apex of the bla
dder. Conclusion. Involution of the urachus is not complete at birth a
nd can be followed up sonographically in the first months of life. Thi
s knowledge should prompt a new strategy in young infants with a disch
arging umbilicus or even an infected urachus. Instead of early surgery
, a conservative approach under sonographic control seems reasonable,
because there is a chance of spontaneous involution and any abnormal d
evelopment can be detected by ultrasound.