Direct effects of contrast media on rat lungs

Despite the widespread use and the assumed safety of Omnipaque (iohexol) and 3% Gastrografin (meglumine diatrizoate) as contrast media for esophagography and computed tomography respectively, their effects on the lung if they are aspirated have never been studied. This information is important because such compounds may inadvertently enter the lungs during the diagnostic procedures. Twenty-four rats were injected intratracheally with 0.15 mL of one of three contrast agents (omnipaque, full-strength Gastrografin and 3% Gastrografin) or normal saline, which was used as a control. Radiographs were then obtained. Equal numbers from each experimental group were sacrificed after 5 minutes, 1 hour and 24 hours, and their lungs were examined pathologically. The rats injected with full-strength Gastrografin all died immediately of gross pulmonary edema. Neither Omnipaque nor 3% Gastrografin was fatal, but Omnipaque produced more edema and alveolar hemorrhage than either normal saline or 3% Gastrografin. Iohexol is, therefore, more irritating to the airways and the lung parenchyma than previously believed.