Supradiaphragmatic accessory liver: a rare cause of respiratory distress in a neonate.

The authors describe a case of supradiaphragmatic accessory liver seen on prenatal ultrasound examinations, mimicking fetal hydrothorax and causing life-threatening respiratory failure after birth. The accessory liver with a transdiaphragmatic pedicle to the caudate lobe of the normal liver was found at throracotomy after failure to expand the lung by chest drainage. The "hydrothorax" turned out to be multilocular mesothelial cyst collection surrounding the ectopic liver. This is the first report of the development of a thoracic accessory liver followed by obstetric ultrasound examinations.