Changes

'''Contrast CT''' is '''[[CT scan|Computed tomography]]''' using (CT) with intravenous (IV) [[radiocontrastcontrast medium]], and in Radlines it refers to a CT scan using IV contrast except otherwise noted. ''':

==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}}

===;When it matters===

[[File:Contrast CT in low GFR.png|thumb|250px260px|center|In case of low GFR, other risk factors need to be checked. Subsequently, the procedure depends on whether the dose that can be given is larger or less than the needed dose.]] ===Other risk factors===Look in the medical records (or ask the patient) for other risk factors of contrast-induced nephropathy. The Roxana Mehran score predictor applies the following ten variables:<ref name=Modi2017>{{cite web|url=https://www.ncbi.nlm.nih.gov/books/NBK448066/|title=Contrast-Induced Nephropathy|website=StatPearls Publishing|year=2017|author=Kalgi Modi, Scott C. Dulebohn}} [http://creativecommons.org/licenses/by/4.0/ CC-BY-4.0]</ref>*Age (4 points if older than 75 years old)*Anemia (3 points)*Use of an intra-aortic balloon pump (5 points)*Decreased real function. In terms of estimated glomerular filtration rate in ml/min::*eGFR 60 to 40 (2 points):*eGFR 40 to 20 (4 points):*eGFR less than 20 (6 points)*Hypotension (5 points, if systolic BP less than 80 mmHg for at least one hour requiring inotropic support)*Contrast media volume (1 point per 100 ml)*Congestive heart failure (5 points)*Diabetes (3 points).A risk score of less than 6 carries a risk of 7.5% to score more than 16 carries up to 57% risk.<ref name=Modi2017/> In addition to those in the Roxana Mehran score, the following are also risk factors of contrast-induced nephropathy:<ref name="NymanAhlkvist2018"/>*Hypoxia*Cirrhosis*NSAIDs or (other) nephrotoxic drugs*Persons in dialysis with residual renal function of at least 400 ml urine / 24h*Individuals who have undergone kidney transplantation ===Adjustment of dose===If and how to adjust the dose depends on supply and demand: ====How much contrast can be given?====In some emergent conditions such as [[CT of aortic aneurysm]] with suspected rupture, the need for contrast is greater than the risk of contrast-induced nephropathy. For the rest of the investigations, evidence suggests that contrast doses should be limited to a ratio of grams of iodine to glomerular filtration rate (I_gram / GFR_ml/min) of a maximum of 1 g/(ml/min).<ref name="KeaneyHannon2013">{{cite journal|last1=Keaney|first1=J. J.|last2=Hannon|first2=C. M.|last3=Murray|first3=P. T.|title=Contrast-induced acute kidney injury: how much contrast is safe?|journal=Nephrology Dialysis Transplantation|volume=28|issue=6|year=2013|pages=1376–1383|issn=0931-0509|doi=10.1093/ndt/gfs602}}</ref> According to European guidelines, the ratio should be less than 1.1 g/(ml/min) for intra-arterial contrast medium administration with first-pass renal exposure (not passing lungs or peripheral tissue before reaching the kidneys).<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> Swedish guidelines are more restrictive, recommending a ratio of less than 0.5 g/(ml/min) in patients with risk factors and irrespective of route of administration, and even more caution in first-pass renal exposure.<ref name="NymanAhlkvist2018"/> {|class="wikitable" align="center"|+ Volume for various Iodine concentrations! I_gram / GFR_ml/min <br>ratio !! 240 mg/ml !! 350 mg/ml !! 370 mg/ml|-| 0.5 || 2.1 ml *GFR_ml/min || 1.4 ml *GFR_ml/min || 1.4 ml *GFR_ml/min|-| 1 || 4.2 ml *GFR_ml/min || 2.9 ml *GFR_ml/min || 2.7 ml *GFR_ml/min|-| 1.1 || 4.6 ml *GFR_ml/min || 3.1 ml *GFR_ml/min || 3.0 ml *GFR_ml/min|} ====How much contrast is needed==== {|class="wikitable"|+ Sufficient volume for normal weight adults!colspan=2 rowspan=2| Exam !!colspan=3| Iodine concentration !!rowspan=2| Comments|-! 300 mg/ml !! 350 mg/ml !! 370 mg/ml|-|colspan=2| [[CT of the head|CT of brain]] || 95ml<ref name=NZ>{{cite web|url=http://www.medsafe.govt.nz/profs/Datasheet/o/Omnipaqueinj.pdf|title=New Zealand Datasheet|website=New Zealand Medicines and Medical Devices Safety Authority|accessdate=2018-10-16}}</ref> || 80 ml<ref name=NZ/> || 75 ml<ref name=NZ/> |||-|rowspan=2| [[CT of the thorax|CT of thorax]] || Overall || 70 - 95 ml<ref name="IezziLarici2017" group="notes">0.3–0.4 gI/kg in a 70kg individual, according to:*{{cite journal|last1=Iezzi|first1=Roberto|last2=Larici|first2=Anna Rita|last3=Franchi|first3=Paola|last4=Marano|first4=Riccardo|last5=Magarelli|first5=Nicola|last6=Posa|first6=Alessandro|last7=Merlino|first7=Biagio|last8=Manfredi|first8=Riccardo|last9=Colosimo|first9=Cesare|title=Tailoring protocols for chest CT applications: when and how?|journal=Diagnostic and Interventional Radiology|volume=23|issue=6|year=2017|pages=420–427|issn=13053825|doi=10.5152/dir.2017.16615}}</ref> || 60 - 80 ml<ref name="IezziLarici2017" group="notes"/> || 55 - 75 ml<ref name="IezziLarici2017" group="notes"/> || Parenchymal changes of the lung can often be evaluated adequately without the use of intravenous contrast.|-| [[CT pulmonary angiogram]] || 20 ml<ref name="LeroyerMeier2016" group="notes">Using dual energy CTA (such as 90/150SnkVp), according to:*{{cite journal|last1=Leroyer|first1=Christophe|last2=Meier|first2=Andreas|last3=Higashigaito|first3=Kai|last4=Martini|first4=Katharina|last5=Wurnig|first5=Moritz|last6=Seifert|first6=Burkhardt|last7=Keller|first7=Dagmar|last8=Frauenfelder|first8=Thomas|last9=Alkadhi|first9=Hatem|title=Dual Energy CT Pulmonary Angiography with 6g Iodine—A Propensity Score-Matched Study|journal=PLOS ONE|volume=11|issue=12|year=2016|pages=e0167214|issn=1932-6203|doi=10.1371/journal.pone.0167214}}</ref> || 17 ml<ref name="LeroyerMeier2016" group="notes"/> || 15 ml<ref name="LeroyerMeier2016" group="notes"/> || Minimal amount when using specific low-contrast protocol.<ref name="LeroyerMeier2016" group="notes"/>|-|rowspan=2| [[CT of the abdomen and pelvis|CT of abdomen]] || Overall || 70 ml<ref name=NZ/> || 60 ml<ref name=NZ/> || 55 ml<ref name=NZ/> || |-| Liver || 55 ml<ref name=Liver group="notes">The liver generally needs an enhancement of at least 30 HU for proper evaluation according to:*{{cite book|title=Multislice CT|edition=3|year=2010|publisher=Springer-Verlag Berlin and Heidelberg GmbH & Co. KG|isbn=9783642069680}}In males at 30 years of age, there is an estimated 0.027 HU of liver parenchymal enhancement per kilogram of body weight and per gram of iodine, when injected at 4 ml per second, according to:*{{cite journal|last1=Bae|first1=Kyongtae T.|title=Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches|journal=Radiology|volume=256|issue=1|year=2010|pages=32–61|issn=0033-8419|doi=10.1148/radiol.10090908}}This example takes the example of a man with a typical weight of 70 kg.</ref> || 45 ml<ref name=Liver group="notes"/> || 40-45 ml<ref name=Liver group="notes"/> || Minimal required amount.<ref name=Liver group="notes"/>|-|colspan=2| [[CT angiography]] || 25 ml<ref name=Angiography group="notes">CT-angiography in a 70kg person, with 100-150 mg I/kg by using 80 kVp, mAs-compensation for constant CNR, fixed injection duration adapted to scan time, automatic bolus tracking and a saline chaser, according to:*{{cite journal|last1=Nyman|first1=Ulf|title=Contrast Medium-Induced Nephropathy (CIN) Gram-Iodine/GFR Ratio to Predict CIN and Strategies to Reduce Contrast Medium Doses|year=2012|doi=10.5772/29992}}</ref> ||colspan=2| 20 ml<ref name=Angiography group="notes"/> || When using specific low-contrast protocol.<ref name=Angiography group="notes"/>|} Departments often have formulas that give the amount of contrast needed for various investigations, using patient sex and weight as main parameters. These may include creatitine levels as well, and in such cases it can help to get a value of of much contrast would hypothetically have been given if the creatinine level was normal, such as for example 80 μmol/L or 0.9 mg/dL. This value can be compared to how much can actually be given in order to determine if it is worth doing the exam with contrast. ===Treating risk factors===Risk factors can sometimes be treated or at least mitigated, especially if having suddenly appeared, such as a decreased renal function when it was previously normal. In such cases a common easily treated cause is dehydration.

'''Hydration'Further reading: [[CT with IV contrast in low renal function]]'' by drinking or intravenous volume expander, either before or after contract administration, decreases the risk of contrast-induced nephropathy.<ref name="YangHiremath2013">{{cite journal|last1=Yang|first1=Xiaoming|last2=Hiremath|first2=Swapnil|last3=Akbari|first3=Ayub|last4=Shabana|first4=Wael|last5=Fergusson|first5=Dean A.|last6=Knoll|first6=Greg A.|title=Prevention of Contrast-Induced Acute Kidney Injury: Is Simple Oral Hydration Similar To Intravenous? A Systematic Review of the Evidence|journal=PLoS ONE|volume=8|issue=3|year=2013|pages=e60009|issn=1932-6203|doi=10.1371/journal.pone.0060009}}</ref>

===Allergy=====Contrast medium reaction===[[File:Injection Sites Intramuscular Thigh Adultsite of adrenaline.pngjpg|300px150px|rightthumb]]

===Pre-medication===;Prevention{{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>

AsthmaIn 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, atopywhen 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 drug -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 food allergy mutagenic effects from its use. There have been regarded as generally not conferring enough risk 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 motivate glucocorticiod premedicationa pregnant mother has no effect on neonatal thyroid function.<ref>{{cite web|url=https://www.cdhaacr.org/~/media/37D84428BF1D4E1B9A3A2918DA9E27A3.pdf|title=ACR Manual on Contrast Media.nshealthVersion 10.ca/3|year=2017|website=Nova Scotia Department American College of Radiology|publisher=American College of Health Radiology Committee on Drugs and WellnessContrast Media|accessdate=20182017-0807-2530}}</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=Guidelines for contrast media preDiagnostic Radiology Procedures on Breastfeeding Patients|website=[[Yale School of Medicine]]|accessdate=2019-07-medication08}} October 2014</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/>

Depending on the purpose of the investigation, there are standardized protocols for time intervals between intravenous radiocontrast administration and image acquisition, in order to visualize the dynamics of contrast enhancements in different organs and tissues.<ref name="Bae2010">{{cite journal|last1=Bae|first1=Kyongtae T.|title=Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches|journal=Radiology|volume=256|issue=1|year=2010|pages=32–61|issn=0033-8419|doi=10.1148/radiol.10090908}}</ref> The main phases thereof are as follows:in table below.<ref name=radiologyassistant>{{cite web|url=http://www.radiologyassistant.nl/en/p52c04470dbd5c/ct-contrast-injection-and-protocols.html|title=CT contrast injection and protocols|author=Robin Smithuis|website=Radiology Assistant|accessdate=2017-12-13}}</ref> '''CT angiography''' is a CT scan corresponding with contrast filling one or more blood vessels of interest.

*[[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>

==Gastrointestinal contrastLocations==See '''Rectally administered contrast[[CT#By location]]''' (CT with IV contrast, including CT angiography, is indicated in cases where a suspicion remains of penetrating trauma to the colon where an initial organized as other CT shows no reason for immediate surgery.<ref>{{cite web|url=http://www.radiologyassistantexaminations).nl/en/p466181ff61073/acute-abdomen-role-of-ct-in-trauma.html#i466184acd2fdb|title=Acute Abdomen - Role of CT in Trauma|author=Stephen Ledbetter and Robin Smithuis|website=Radiopaedia|date=2007-08-02}}</ref>