Sonomorphology and involution of the normal urachus in asymptomatic newborns

The number of reports on the sonomorphology of the urachus or urachal remnants in neonates and the pattern of involution is limited.

To determine whether a sonographically visible urachus in the first months of life is a pathologic condition and whether postnatal involution can be demonstrated by ultrasound.

A total of 102 asymptomatic infants (premature and term newborns) were examined with a high-resolution 7.5-MHz linear transducer between 0 and 60 days of age. In 70 infants, a second examination followed 3-5 months later.

In all infants, the urachus could be identified on the first examination. Different morphological types were differentiated. There was no difference between premature and term newborns in the morphology of the urachus. Spontaneous involution of the urachus was observed in all infants receiving a second examination, and they most often showed a fusiform urachal remnant at the apex of the bladder.

Involution of the urachus is not complete at birth and can be followed up sonographically in the first months of life. This knowledge should prompt a new strategy in young infants with a discharging 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 development can be detected by ultrasound.