Radiocontrast agent

<h2 id="types-and-uses">Types and uses</h2>
<p>Radiocontrast agents used in <a href="/facts/X-ray/wseP79cN">X-ray</a> examinations can be grouped in positive (iodinated agents, barium sulfate), and negative agents (air, carbon dioxide, methylcellulose).<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a>
</p>
<h3>Iodine (circulatory system)</h3>

<p class="note">Main article: <a href="/facts/Iodinated_contrast/WCkoRRyE">Iodinated contrast</a></p>
<p><a href="/facts/Iodinated_contrast/WCkoRRyE">Iodinated contrast</a> contains <a href="/facts/Iodine/JlfMecMf">iodine</a>. It is the main type of radiocontrast used for <a href="/facts/Intravenous_administration/AwwuD3Nu">intravenous administration</a>. Iodine has a particular advantage as a contrast agent for radiography because its innermost electron ("k-shell") binding energy is 33.2 keV, similar to the average energy of x-rays used in diagnostic radiography. When the incident x-ray energy is closer to the k-edge of the atom it encounters, photoelectric absorption is more likely to occur. Its uses include:
</p>
<ul><li><a href="/facts/Contrast_CT/t9jG2qBc">Contrast CTs</a></li>
<li><a href="/facts/Angiography/4onftT3X">Angiography</a> (<i>arterial investigations</i>)</li>
<li><a href="/facts/Venography/5gbHeItq">Venography</a> (<i>venous investigations</i>)</li>
<li>VCUG (<i><a href="/facts/Voiding_cystourethrogram/jhNKBBK3">voiding cystourethrography</a></i>)</li>
<li>HSG (<i><a href="/facts/Hysterosalpingogram/Hsb0dnse">hysterosalpingogram</a></i>)</li>
<li>IVU (<i>intravenous <a href="/facts/Urography/Je38eg2y">urography</a></i>)</li></ul>
<p>Organic iodine molecules used for contrast include <a href="/facts/Iohexol/QQso6Dkm">iohexol</a>, <a href="/facts/Iodixanol/alebfbvK">iodixanol</a> and <a href="/facts/Ioversol/RkGa5jN8">ioversol</a>.
</p>
<h3>Barium sulfate (digestive system)</h3>

<p><a href="/facts/Barium_sulfate/QrjdoS1k">Barium sulfate</a> is mainly used in the imaging of the digestive system. The substance exists as a water-insoluble white powder that is made into a slurry with water and administered directly into the <a href="/facts/Gastrointestinal_tract/nK2zwqBS">gastrointestinal tract</a>.
</p>
<ul><li><a href="/facts/Upper_gastrointestinal_series/FfkL02fs">Upper gastrointestinal series</a></li>
<li><a href="/facts/Lower_gastrointestinal_series/oT6nXkFJ">Barium enema</a> (<i>large bowel investigation</i>) and DCBE (<i>double contrast barium enema</i>).</li>
<li>Barium swallow (<i>oesophageal investigation</i>)</li>
<li>Barium meal (<i>stomach investigation</i>) and double contrast barium meal</li>
<li>Barium follow through (<i>stomach and small bowel investigation</i>)</li>
<li>CT pneumocolon / virtual colonoscopy</li></ul>
<p>Barium sulfate, an insoluble white powder, is typically used for enhancing contrast in the GI tract. Depending on how it is to be administered the compound is mixed with water, thickeners, de-clumping agents, and flavourings to make the contrast agent. As the barium sulfate doesn't dissolve, this type of contrast agent is an opaque white mixture. It is only used in the digestive tract; it is usually swallowed as a <a href="/facts/Barium_sulfate_suspension/CaqcKWp6">barium sulfate suspension</a> or administered as an enema. After the examination, it leaves the body with the <a href="/facts/Feces/r9HDKB8G">feces</a>.
</p>
<h3>Air</h3>
<p>As in the picture on the right where both air and barium are used together (hence the term "double-contrast" barium enema) air can be used as a contrast material because it is <i>less</i> radio-opaque than the tissues it is defining. In the picture it highlights the interior of the colon. An example of a technique using purely air for the contrast medium is an air arthrogram where the injection of air into a joint cavity allows the cartilage covering the ends of the bones to be visualized.
</p><p>Before the advent of modern <a href="/facts/Neuroimaging/dA5Cteaf">neuroimaging</a> techniques, air or other gases were used as contrast agents employed to displace the <a href="/facts/Cerebrospinal_fluid/tcWG7hhv">cerebrospinal fluid</a> in the brain while performing a <a href="/facts/Pneumoencephalography/847d6yhk">pneumoencephalography</a>. Sometimes called an "air study", this once common yet highly-unpleasant procedure was used to enhance the outline of structures in the brain, looking for shape distortions caused by the presence of lesions.
</p>
<h3>Carbon dioxide</h3>
<p class="note">Main article: <a href="/facts/Carbon-dioxide_angiography/FRayHJvA">Carbon-dioxide angiography</a></p>
<p>Carbon dioxide also has a role in angioplasty. It is low-risk as it is a natural product with no risk of allergic potential. However, it can be used only below the diaphragm as there is a risk of embolism in neurovascular procedures. It must be used carefully to avoid contamination with room air when injected. It is a negative contrast agent in that it displaces blood when injected intravascularly.
</p>
<h3>Discontinued agents</h3>
<h4>Thorotrast</h4>
<p><a href="/facts/Thorotrast/VFQ19JKa">Thorotrast</a> was a contrast agent based on <a href="/facts/Thorium_dioxide/wboPx2It">thorium dioxide</a>, which is <a href="/facts/Radioactive/Ya6FVjt4">radioactive</a>. It was first introduced in 1929. While it provided good image enhancement, its use was abandoned in the late 1950s since it turned out to be <a href="/facts/Carcinogenic/soH8Y9CE">carcinogenic</a>. Given that the substance remained in the bodies of those to whom it was administered, it gave a continuous radiation exposure and was associated with a risk of cancers of the liver, bile ducts and bones, as well as higher rates of <a href="/facts/Hematological_malignancy/tzyyShka">hematological malignancy</a> (leukemia and lymphoma).<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> Thorotrast may have been administered to millions of patients prior to being disused.
</p>
<h4>Nonsoluble substances</h4>
<p>In the past, some non water-soluble contrast agents were used. One such substance was <a href="/facts/Iofendylate/F38N0mIB">iofendylate</a> (trade names: Pantopaque, Myodil) which was an iodinated oil-based substance that was commonly used in <a href="/facts/Myelography/LISeaw1W">myelography</a>. Due to it being oil-based, it was recommended that the physician remove it from the patient at the end of the procedure. This was a painful and difficult step and because complete removal could not always be achieved, iofendylate's persistence in the body might sometimes lead to <a href="/facts/Arachnoiditis/8eIT0Qe9">arachnoiditis</a>, a potentially painful and debilitating lifelong disorder of the spine.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a><a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> Iofendylate's use ceased when water-soluble agents (such as <a href="/facts/Metrizamide/A5mAKPxC">metrizamide</a>) became available in the late 1970s. Also, with the advent of <a href="/facts/Magnetic_resonance_imaging/Vh9yG9qq">MRI</a>, myelography became much less-commonly performed.
</p>
<h2 id="adverse-effects">Adverse effects</h2>
<p class="note">Further information: <a href="/facts/Iodinated_contrast/WCkoRRyE">Iodinated contrast</a></p>
<p>Modern iodinated contrast agents – especially non-ionic compounds – are generally well tolerated.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> The adverse effects of radiocontrast can be subdivided into type A reactions (e.g. thyrotoxicosis), and type B reactions (hypersensitivity reactions: allergy and non-allergy reactions [formerly called anaphylactoid reactions]).<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a>
</p><p>Patients receiving contrast via IV typically experience a hot feeling around the throat, and this hot sensation gradually moves down to the pelvic area.
</p><p>The documentation of adverse drug reactions to contrast media should be documented precisely so that the patient receives adequate prophylaxis if contrast medium is administered again. <a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a>
</p>
<h3>Contrast induced nephropathy</h3>
<p class="note">Main article: <a href="/facts/Contrast-induced_nephropathy/08UrWtQD">Contrast-induced nephropathy</a></p>
<p>Iodinated contrast may be <a href="/facts/Nephrotoxicity/QaWn5pwB">toxic to the kidneys</a>, especially when given via the arteries prior to studies such as catheter coronary angiography. Non-ionic contrast agents, which are almost exclusively used in <a href="/facts/Computed_tomography/NusPJ2S8">computed tomography</a> studies, have not been shown to cause CIN when given intravenously at doses needed for CT studies.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a>
</p>
<h3>Thyroid dysfunction</h3>
<p>Iodinated radiocontrast can induce <a href="/facts/Hyperthyroidism/H9Eqmbgk">overactivity</a> (hyperthyroidism) and <a href="/facts/Hypothyroidism/oqtQDu2F">underactivity</a> (hypothyroidism) of the thyroid gland. The risk of either condition developing after a single examination is 2–3 times that of those who have not undergone a scan with iodinated contrast. Thyroid underactivity is mediated by two phenomena called the <a href="/facts/Plummer_effect/XDzGuJjn">Plummer</a> and <a href="/facts/Wolff%E2%80%93Chaikoff_effect/F540kunz">Wolff–Chaikoff effect</a>, 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 <a href="/facts/Jod-Basedow_phenomenon/9a3aVMnu">Jod-Basedow phenomenon</a>, where the iodine induces overproduction of thyroid hormone; this may be the result of underlying thyroid disease (such as nodules or <a href="/facts/Graves%27_disease/6CjnWNdE">Graves' disease</a>) or previous iodine deficiency. Children exposed to iodinated contrast during pregnancy may develop hypothyroidism after birth and monitoring of the thyroid function is recommended.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a>
</p>
<h2 id="see-also">See also</h2>
<ul>
<li>Medicine portal</li></ul>

<h2 id="external-links">External links</h2>
<ul><li> Media related to Radiocontrast agents at Wikimedia Commons</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Dong, Yuxy C; Cormode, David P. (2021). "Chapter 17. Heavy Elements for X-Ray Contrast". Metal Ions in Bio-Imaging Techniques. Springer. pp. 457–484. doi:10.1515/9783110685701-023. S2CID 233676619. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Grosche, B.; Birschwilks, M.; Wesch, H.; Kaul, A.; van Kaick, G. (6 May 2016). "The German Thorotrast Cohort Study: a review and how to get access to the data". Radiation and Environmental Biophysics. 55 (3): 281–289. doi:10.1007/s00411-016-0651-8. PMID 27154786. S2CID 45053720. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Dunlevy, Sue (10 December 2016). "Australians crippled and in chronic pain from dye used in toxic X-rays". The Daily Telegraph (Sydney). Retrieved 27 October 2017. <a href="http://www.dailytelegraph.com.au/lifestyle/health/australians-crippled-and-in-chronic-pain-from-dye-used-in-toxic-xrays/news-story/e35f258d50c2508c214809896673da88" target="_blank">http://www.dailytelegraph.com.au/lifestyle/health/australians-crippled-and-in-chronic-pain-from-dye-used-in-toxic-xrays/news-story/e35f258d50c2508c214809896673da88</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>William P. Dillon; Christopher F. Dowd (2014). "Chapter 53 – Neurologic Complications of Imaging Procedures". Aminoff's Neurology and General Medicine (5th ed.). pp. 1089–1105. <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>Haberfeld, H, ed. (2009). Austria-Codex (in German) (2009/2010 ed.). Vienna: Österreichischer Apothekerverlag. ISBN 978-3-85200-196-8. <a href="978-3-85200-196-8" target="_blank">978-3-85200-196-8</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>Boehm I, Morelli J, Nairz K, Silva Hasembank Keller P, Heverhagen JT (2017). "Myths and misconceptions concerning contrast media induced anaphylaxis: a narrative review". Postgrad Med. 129 (2): 259–266. doi:10.1080/00325481.2017.1282296. PMID 28085538. S2CID 205452727. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
<li id="fn:7"><p>Böhm IB, van der Molen AJ (2020). "Recommendations for Standardized Documentation of Contrast Medium-Induced Hypersensitivity". J Am Coll Radiol. 17 (8): 1027–1028. doi:10.1016/j.jacr.2020.02.007. hdl:1887/3184447. PMID 32142634. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li>
<li id="fn:8"><p>McDonald, Robert; McDonald, Jennifer S.; Carter, Rickey E.; Hartman, Robert P.; Katzberg, Richard W.; Kallmes, David F.; Williamson, Eric E. (December 2014). "Intravenous Contrast Material Exposure Is Not an Independent Risk Factor for Dialysis or Mortality". Radiology. 273 (3): 714–725. doi:10.1148/radiol.14132418. PMID 25203000. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li>
<li id="fn:9"><p>Lee SY, Rhee CM, Leung AM, Braverman LE, Brent GA, Pearce EN (6 November 2014). "A Review: Radiographic Iodinated Contrast Media-Induced Thyroid Dysfunction". J Clin Endocrinol Metab. 100 (2): 376–83. doi:10.1210/jc.2014-3292. PMC 4318903. PMID 25375985. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4318903" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4318903</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li>
</ol>

Radiocontrast agent open-in-new

Radiocontrast agent