<s>[INST] context: "Iodinated contrast Materials Water-soluble iodinated contrast media can be used to visualize the upper gastrointestinal tract. These contrast material are considered safer than barium sulfate in patients with esophageal perforation or communication between esophagus and airways and when there is a risk of aspiration onto the bronchi. They are also used for the examination of the esophagus in the early postoperative period following esophageal surgery or correction of hiatal hernia. The demonstration of leak is a contraindication for the withdrawal of the postoperative gastric tube. Water-soluble- Water-soluble iodinated contrast media can be classified by osmolality. High osmolality contrast media- High osmolality contrast media (HOCM) are approximately five to eight times the osmolality of serum. diatrizoate sodium/meglumine (Gastrografin, MD-Gastroview, Cystografin) iothalamate sodium/meglumine (Conray, Cysto-Conray) Low osmolality contrast media-Low osmolality contrast media (LOCM) are less than three times the osmolality of human serum and preferred for intravascular and intrathecal administration iopamidol (Isovue) iohexol (Omnipaque) - most safest used iopromide (Ultravist) ioversol (Optiray) ioxilan (Oxilan) [/INST] question: Safest contrast in esophageal perforation: | options: A: Iohexol B: Barium sulphate C: Gadolinium D: Hypaque | answer: A </s>