<prompt> Safest contrast in esophageal perforationIohexolBarium sulphateGadoliniumMethylene blue  <response>: Ans. a IohexolRef: Shackelford, 7th Edition, Page 86Contrasts to detect leak and perforation:Two contrasts are commonly used to detect perforation Barium Water soluble contrasts: Low osmolar: Iohexol, Metrizamide High Osmolar: Diatrazoate Gastrograffin High osmolar Gastrograffin Diatrozoate meglumine: has more chances of pulmonary edema than low osmolar contrasts like Iohexol Omnipaque and metrizamide Amnipaque.In conclusion: Best to diagnose perforations - High density Barium Safest in usage: Low osmolar Water soluble contrasts like Iohexol and Metrizamide 