Contrast dyes are divided into three groups based on their osmolarity. High-osmolar contrast medium (HOCM), the oldest and most nephrotoxic group, is no longer used. Most studies are currently performed with either low-osmolar contrast medium (LOCM) or iso-osmolar contrast medium (IOCM): #Nephrology #IVContrast #Dyes #Classification #HighOsmolarity #LowOsmolarity #Osmolality #Ioxhexol #Omnipaque #Visipaque