The ultrasonographic pseudo-double contour sign in calcium pyrophosphate deposition disease: an anatomic explanation and how to distinguish it from gout.

Address: Department of Rheumatology, IRCCS Istituto Ortopedico Galeazzi, Milan, Italy.; Unit of Human Anatomy and Embryology Department of Pathology and Experimental Therapeutics Faculty of Medicine and Health Sciences, University of Barcelona Bellvitge Campus, Barcelona, Spain.; Instituto Poal de Reumatologia, University of Barcelona and Vall d'Hebron Hospital, Barcelona, Spain.; Department of Clinical Science and Community Health, Università Degli Studi di Milano, Milan, Italy.; Division of RheumatologyDepartment of Experimental and Clinical Medicine Azienda Ospedaliero Universitaria Careggi, University of Florence, Florence, Italy.; Department of Women's and Children's Health, University of Padova, Padova, Italy.; Faculty of Medicine and Health Sciences, University of Barcelona Bellvitge Campus and Instituto Poal de Reumatologia University of Barcelona, Barcelona, Spain.