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===;When it matters===
===;Prevention===
==Hyperthyroidism==
Patients at risk for contrast-induced hyperthyroidism are mainly those with diagnosed yet untreated hyperthyroidism, which may motivate contrast-free alternatives such as using a different modality.<ref name=UpToDate-thyr>{{cite web|url=https://www.uptodate.com/contents/iodine-induced-thyroid-dysfunction|title=Iodine-induced thyroid dysfunction|author=Martin I Surks, MD|website=UpToDate}} This topic last updated: Apr 02, 2019.</ref>
In older patients with multinodular goiter and borderline low or subnormal TSH concentrations, a suggested measure is measurement of thyroid function tests three to four weeks after contrast administration.<ref name=UpToDate-thyr/> Limited evidence suggests that antithyroid agents before the investigation may blunt or prevent hyperthyroidism.<ref name=UpToDate-thyr/>
→Phases: Corrected
'''Washout''' is where tissue loads radiocontrast during arterial phase, but then returns to a rather hypodense state in venous or later phases. This is a property of for example [[hepatocellular carcinoma]] as compared to the rest of the liver parenchyma.<ref name="ChoiLee2014">{{cite journal|last1=Choi|first1=Jin-Young|last2=Lee|first2=Jeong-Min|last3=Sirlin|first3=Claude B.|title=CT and MR Imaging Diagnosis and Staging of Hepatocellular Carcinoma: Part II. Extracellular Agents, Hepatobiliary Agents, and Ancillary Imaging Features|journal=Radiology|volume=273|issue=1|year=2014|pages=30–50|issn=0033-8419|doi=10.1148/radiol.14132362|pmc=4263770|pmid=25247563}}</ref>
==Risk factors==In Swedish practice<ref>{{NU Hospital Group}}</ref> the standard risk factor questions include presence or absence of:*Renal or urinary disease*Thyroid disorders*Myasthenia gravis: Older forms of iodinated contrast have caused an increased risk of exacerbation of the disease, but modern forms have no immediate increased risk.<ref name="MehriziPascuzzi2014">{{cite journal|last1=Mehrizi|first1=Mehyar|last2=Pascuzzi|first2=Robert M.|title=Complications of radiologic contrast in patients with myasthenia gravis|journal=Muscle & Nerve|volume=50|issue=3|year=2014|pages=443–444|issn=0148639X|doi=10.1002/mus.24254|pmid=24677227}}</ref>*Diabetes and heart disease: These are aggravating factors in low renal function (see [[CT with IV contrast in low renal function]]) ===Low renal function===
{{Main|CT with IV contrast in low renal function}}
Decreased renal function and several other conditions increase the risk of '''contrast-induced nephropathy''', which is a potentially lethal renal injury to the kidney following intravenous radiocontrast.<ref name="RudnickFeldman2008">{{cite journal|last1=Rudnick|first1=M.|last2=Feldman|first2=H.|title=Contrast-Induced Nephropathy: What Are the True Clinical Consequences?|journal=Clinical Journal of the American Society of Nephrology|volume=3|issue=1|year=2008|pages=263–272|issn=1555-9041|doi=10.2215/CJN.03690907}}</ref>
According to European guidelines, the main risk factors of ''contrast-induced nephropathy'':<ref name="NymanAhlkvist2018">{{cite journal|last1=Nyman|first1=Ulf|last2=Ahlkvist|first2=Joanna|last3=Aspelin|first3=Peter|last4=Brismar|first4=Torkel|last5=Frid|first5=Anders|last6=Hellström|first6=Mikael|last7=Liss|first7=Per|last8=Sterner|first8=Gunnar|last9=Leander|first9=Peter|title=Preventing contrast medium-induced acute kidney injury|journal=European Radiology|year=2018|issn=0938-7994|doi=10.1007/s00330-018-5678-6}}</ref>
*Estimated glomerular filtration rate (eGFR) of less than '''30 ml/min'''/1.73 m2 before intra-venous or intra-arterial radiocontrast administration with second-pass renal exposure (passing lungs or other tissues before the kidneys).
''Further reading: [[CT with IV contrast in low renal function]]''
===Allergy===
[[File:Intramuscular site of adrenaline.jpg|150px|thumb]]
{{Main|Contrast medium reaction}}
*Summon an '''anesthesiologist'''
{{Main|Prevention of contrast medium reaction}}
Before a contrast CT of a patient with known allergic-like or unknown-type of contrast reaction to the same class of contrast medium (such as iodinated), the American College of of Radiology recommends premedication with a glucocorticoid, preferably starting 12 or 13 hours before contrast administration.<ref>{{cite web|url=https://www.acr.org/-/media/ACR/Files/Clinical-Resources/Contrast_Media.pdf#page=11|title=Page 9 in: ACR Manual on On Contrast Media|website=American College of Radiology, Committee on Drugs and Contrast Media|accessdate=2018-08-25}} Version 10.3. 2018. ACR </ref> ===Hyperthyroidism===Patients at risk for contrast-induced hyperthyroidism are mainly those with diagnosed yet untreated hyperthyroidism, which may motivate contrast-free alternatives such as using a different modality.<ref name=UpToDate-thyr>{{cite web|url=https://www.uptodate.com/contents/iodine-induced-thyroid-dysfunction|title=Iodine-induced thyroid dysfunction|author=Martin I Surks, MD|website=UpToDate}} This topic last updated: Apr 02, 2019.</ref> In older patients with multinodular goiter and borderline low or subnormal TSH concentrations, a suggested measure is measurement of thyroid function tests three to four weeks after contrast administration.<ref name=UpToDate-thyr/> Limited evidence suggests that antithyroid agents before the investigation may blunt or prevent hyperthyroidism.<ref name=UpToDate-thyr/> ===Pregnancy===Iodinated contrast in pregnancy, when orally administered, is harmless.<ref name=acog>{{cite web|url=https://www.acog.org/Resources-And-Publications/Committee-Opinions/Committee-on-Obstetric-Practice/Guidelines-for-Diagnostic-Imaging-During-Pregnancy-and-Lactation|title=Guidelines for Diagnostic Imaging During Pregnancy and Lactation|website=[[American Congress of Obstetricians and Gynecologists]]}} February 2016</ref> Intravenous administration of iodinated radiocontrast agents can cross the placenta and enter the fetal circulation, but animal studies have reported no teratogenic or mutagenic effects from its use. There have been theoretical concerns about potential harm of free iodide on the fetal thyroid gland,<ref name=acog/> but multiple studies have shown that a single dose of intravenously administered iodinated contrast medium to a pregnant mother has no effect on neonatal thyroid function.<ref>{{cite web|url=https://www.acr.org/~/media/37D84428BF1D4E1B9A3A2918DA9E27A3.pdf|title=ACR Manual on Contrast Media. Version 10.3|year=2017|website=American College of Radiology|publisher=American College of Radiology Committee on Drugs and Contrast Media|accessdate=2017-07-30}}</ref> Nevertheless, it generally is recommended that radiocontrast only be used if absolutely required to obtain additional diagnostic information that will improve the care of the fetus or mother.<ref name=acog/> ===Breastfeeding===American College of Radiology guidelines state that iodinated contrast administration to a breastfeeding mother is considered safe for both the mother and child.<ref name=yale>{{cite web|url=https://medicine.yale.edu/diagnosticradiology/patientcare/policies/breastfeeding.aspx|title=Diagnostic Radiology Procedures on Breastfeeding Patients|website=[[Yale School of Medicine]]|accessdate=2019-07-08}}</ref> Still, mothers who remain concerned about any potential adverse effects to the child are recommended to have the option of abstaining from breastfeeding for 24 hours, with continued milk extraction such as by a breast pump during that period.<ref name=yale/> Mothers that opt for this for non-emergent exams may also use a breast pump to obtain milk before the exam in order to feed the child during the 24-hour abstinence period.<ref name=yale/>
==Phases==
| 6-13 sec<ref name=IFMBE>[https://books.google.se/books?id=oVGjnOLXUgkC&pg=PA584 Page 584] in: {{cite book|title=5th European Conference of the International Federation for Medical and Biological Engineering 14 - 18 September 2011, Budapest, Hungary. Volume 37 of IFMBE Proceedings|author=Ákos Jobbágy|publisher=Springer Science & Business Media|year=2012|isbn=9783642235085}}</ref> || -
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*[[Pulmonary CT of pulmonary embolism]](can use [[bolus tracking]] in [[pulmonary trunk]] + 6 seconds)<ref>{{cite web|url=https://posterng.netkey.at/esr/viewing/index.php?module=viewing_poster&doi=10.1594/ecr2018/C-1831|title=Introducing the use of Flash CTPA; how does it compare to standard CTPA?|website=Postering|author=Pavan Nandra|year=2018}}</ref>
|-
! [[Pulmonary vein|Pulmonary venous]] phase
*Disappearance of contrast in all abdominal structures except for tissue with [[fibrosis]], which appears more radiodense.
|}
==Locations==
