Zeman Robert K.; Kamel, Perry L. M.D.; Vanagunas, Arvydas M.D.Journal of Clinical Gastroenterology: August 1991 Lessons in Clinical Radiology: PDF Only Buy Abstract Endoscopic retrograde cholangiography (ERC) is the “gold standard” for the preoperative diagnosis of chole-docholithiasis. 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. © Lippincott-Raven Publishers.