Myelograms like this one from a horse are performed using soluble nonionic organic iodides (e.g., iohexol, iopamidol, and iotolan). They are still hyperosmolar but less so than ionic organic iodides. Thus, there is a lower incidence of adverse reactions.
Soluble ionic organic iodides (e.g., iothalamate, diatrizoate) can be used orally for gastrointestinal studies; intravascularly; in joints, the urinary tract and the abdomen; in wounds; and in salivary ducts. They should NOT be used intrathecally for myelography.
Insoluble inert radiopaque medium such as barium sulfate is used for gastrointestinal motility studies. Radiolucent gases (e.g., nitrous oxide, air, and carbon dioxide) can be used for double-contrast cystograms and gastrograms.
Image courtesy of Nora Grenager, VMD, DACVIM.
