Floating common bile duct stones. A cause of a false negative endoscopic retrograde cholangiogram

Endoscopic retrograde cholangiography (ERC) is the "gold standard" for the preoperative diagnosis of choledocholithiasis. Air bubbles that can cause a false positive ERC are differentiated from stones by their response to gravitational maneuvers: bubbles rise while stones sink. We report a patient with round, floating common bile duct stones that mimicked air bubbles to be the reason for a false negative ERC.