Megacystis associated with an umbilical cord cyst: a sonographic feature of a patent urachus in the first trimester.

OBJECTIVE

The purpose of this series was to report the first-trimester sonographic findings, antenatal course, and outcome in fetuses with a patent urachus.

METHODS

We conducted a review of ultrasound reports and medical charts from 3 pregnancies complicated by a congenital patent urachus detected in the first trimester.

RESULTS

All 3 fetuses had megacystis and an umbilical cord cyst close to the fetal abdominal insertion that was detected in the first trimester. In 2 cases, the megacystis resolved spontaneously while the umbilical cord cyst worsened in appearance; among them, massive edema of the umbilical cord was documented in 1, and evidence of partial bladder exstrophy was detected in the third trimester in the other. Both cases required neonatal surgery with no complications. In the remaining case, the fetus died in the early second trimester. Postmortem examination confirmed the diagnosis of a patent urachus, an allantoic cyst, and thrombosis of the umbilical vessels.

CONCLUSIONS

Megacystis is a warning sign of a patent urachus in the first trimester. The prognosis of this condition is generally good; however, fetal death can occur secondary to compression of umbilical vessels due to the expanding allantoic cyst.