Iodinated contrast
Iodinated contrast is a form of intravenous radiocontrast (radiographic dye) containing iodine, which enhances the visibility of vascular structures and organs during radiographic procedures. Some pathologies, such as cancer, have particularly improved visibility with iodinated contrast.
Iodinated contrast media may either be oil-based or water-soluble, the former of which is slowly absorbed by body tissue and is usually only used in sialographic and hysterosalpingographic examinations. Water-soluble iodinated medium, which is more quickly absorbed, may be used in place of barium sulfate for gastrointestinal studies that are contraindicated by the use of barium for that reason.
Iodinated medium may also be either ionic or non-ionic. The ionic type tends to create a high osmolality in blood and may cause a contrast media reaction in some individuals, which may be life-threatening for those with certain medical conditions. The non-ionic form decreases this risk, but is much more expensive. The non-ionic contrast media is much more widely used today.
Shortly after infusion, iodinated contrast medium causes a warming sensation throughout the body. Sometimes this feeling is more pronounced in the pelvic area. Patients receiving contrast via IV typically experience a hot feeling around the throat, and this hot sensation gradually moves down to the pelvic area.
Iodinated contrast is toxic to the kidneys and kidney function of the patient receiving a dose should be considered before the exam. The estimated glomerular filtration rate (eGFR) should be no lower than 30 mL/min in patients receiving iodinated contrast, and discretion should be used in patients with eGFR less 45 mL/min.[1] Following up with extra fluids after an injection is highly recommended.
Iodinated radiocontract can induce overactivity (hyperthyroidism) and underactivity (hypothyroidism) of the thyroid gland. The risk of either condition developing after a single examination is 2-3 times that those who have not undergone a scan with iodinated contrast. Thyroid underactivity is mediated by a phenomenon called the Wolff–Chaikoff effect, where iodine suppresses the production of thyroid hormones; this is usually temporary but there is an association with longer-term thyroid underactivity. Some other people show the opposite effect, called Jod-Basedow phenomenon, where the iodine induces overproduction of thyroid hormone; this may be the result of underlying thyroid disease (such as nodules or Graves' disease) or previous iodine deficiency. Children exposed to iodinated contrast during pregnancy may develop hypothyroidism after birth and monitoring of the thyroid function is recommended.[2]
Further reading
- Bontranger, Kenneth L. & Lampignano, John P. (2005). Radiographic Positioning and Related Anatomy, St. Louis: Elsevier Mosby. ISBN 0-323-02507-2.
References
- ↑ , UC San Francisco Guidelines on the Administration of Intravenous Iodinated Contrast Media
- ↑ Lee SY, Rhee CM, Leung AM, Braverman LE, Brent GA, Pearce EN (6 Nov 2014). "A Review: Radiographic Iodinated Contrast Media-Induced Thyroid Dysfunction". J Clin Endocrinol Metab. Online first. doi:10.1210/jc.2014-3292. PMID 25375985.