Patent urachus with an allantoic cyst is extremely rare. The urachus is a remnant fibrous tissue of the fetal allantois which should involute into the median umbilical ligament. The failure of this involution results in an open cystic tract communicating the umbilicus to the fetal bladder.

The differential diagnosis should include omphalocele and bladder exstrophy.

The treatment is surgical.