Platypnea-orthodeoxia syndrome (POS) is a rare syndrome of severe hypoxemia upon assuming an upright position. It is classically described as shunting from the right atrium to the left atrium usually via a patent foramen ovale (PFO). Alterations in the intrathoracic anatomy after liver resection and regeneration may trigger this condition in patients with clinically silent PFO -a previously unreported cause of POS.