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==Actions=====Underweight or overweight?===
→Other risk factors: Linked
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In [[CT with IV contrast]], 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>
*Multiple radiocontrast injections within 48-72 h
[[File:Contrast CT in low GFR.png|thumb|265px|center|Other In people at risk for contrast-induced nephropathy, other risk factors need to be checked. Subsequently, the procedure depends most relevant options depend on whether the dose that can be given is larger, about equal, or less than the needed dose.]]
==Other risk factors==
*Individuals who have undergone kidney transplantation
Metformin use potentially causes lactic acidosis if contrast-induced nephropathy occurs, and according to European guidelines it should be stopped (ESUR) recommends stopping metformin at least 48 hours before a CT with IV contrast if GFR is between 30 and 44 ml/min/1.73 m<sup>2</sup>, unless emergent, and resume metformin 48 hours after the CT if renal function has not deteriorated. If lower, no contrast should be given unless absolutely necessary.<ref>{{cite web|url=http://www.esur.org/guidelines/|website=ESUR|accessdate=2018-11-09|title=Iodine-based contrast media}}</ref> In such cases, Swedish guidelines only include withholding metformin ''after'' the CT, and not before.<ref>{{cite web|url=file:///C:/Users/mikha19/Downloads/Nationella_rek_metformin_kontrastmedel_v61_2018-05-07.pdf|title=Nationella rekommendationer: Svensk uroradiologisk förenings kontrastmedelsgrupp: METFORMIN. Version 6.1|date=2018-05-07}}</ref>
Other relative or absolute contraindications to IV contrast, regardless of GFR, are contrast allergy ''(see [[CT_with_IV_contrastCT with IV contrast#Allergy|contrast allergy]] )'' and untreated hyperthyroidism''(see [[Iodinated contrast and hyperthyroidism]])''.
==How much contrast can be given?==
*{{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.
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| [[CT of pulmonary angiogramembolism]] || 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"/>
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At moderate weight deviations, corrections can be made by adjusting contrast dose proportionally to patient weight. Still, the needed dose is actually proportional to the ''lean body weight'' of the patient. For both men and women weighing more than about 85 kg,<ref group="notes">At above this weight, calculated contrast amount with the Boer formula deviates more than 10% from both the weight-unadjusted amount, as well as the amount taken proportionally to the weight, for both men and women.</ref> contrast dose is optimally calculated by the Boer formula, using height and weight of the patient.<ref name="CarusoDe Santis2018">{{cite journal|last1=Caruso|first1=Damiano|last2=De Santis|first2=Domenico|last3=Rivosecchi|first3=Flaminia|last4=Zerunian|first4=Marta|last5=Panvini|first5=Nicola|last6=Montesano|first6=Marta|last7=Biondi|first7=Tommaso|last8=Bellini|first8=Davide|last9=Rengo|first9=Marco|last10=Laghi|first10=Andrea|title=Lean Body Weight-Tailored Iodinated Contrast Injection in Obese Patient: Boer versus James Formula|journal=BioMed Research International|volume=2018|year=2018|pages=1–6|issn=2314-6133|doi=10.1155/2018/8521893}}</ref> Taking this formula, the needed volume of IV contrast from the unadjusted volume given in the table above becomes:
[[File:Diagram - weight.png|thumb|Boer formula for volume of contrast in a normal height patient if having received 60 ml if weight was normal.<ref group="notes">176 cm male and 162 cm female</ref>]]
Still, it is generally enough to make a rough estimation of the needed contrast, since there are for example inherent standard deviations in the usage of creatinine or cystatin C in calculating GFR.
==Actions==
===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''' should be done in patients with suspected dehydration (such as recent vomiting, diarrhea and/or diuretic use), and is done by drinking or by intravenous volume expander, either before or after contract administration, decreases the risk of contrast-induced nephropathy. Hydration should be avoided otherwise.<ref namegroup="YangHiremath2013notes">Hydration of people with low renal function, without separating dehydrated from non-dehydrated individuals, seems to only increase complication rates, including electrolyte imbalances and cardiac arrhythmias:<br>{{cite journal|last1=YangNijssen|first1=XiaomingEstelle C|last2=HiremathRennenberg|first2=SwapnilRoger J|last3=AkbariNelemans|first3=AyubPatty J|last4=ShabanaEssers|first4=WaelBrigitte A|last5=FergussonJanssen|first5=Dean A.Marga M|last6=KnollVermeeren|first6=Greg Marja A.|last7=Ommen|first7=Vincent van|last8=Wildberger|first8=Joachim E|title=Prevention Prophylactic hydration to protect renal function from intravascular iodinated contrast material in patients at high risk of Contrastcontrast-Induced Acute Kidney Injuryinduced nephropathy (AMACING): Is Simple Oral Hydration Similar To Intravenous? A Systematic Review of the Evidencea prospective, randomised, phase 3, controlled, open-label, non-inferiority trial|journal=PLoS ONEThe Lancet|volume=8389|issue=310076|year=20132017|pages=e600091312–1322|issn=1932-620301406736|doi=10.13711016/journal.pone.0060009S0140-6736(17)30057-0}}</ref> ===Adjust radiation===Use low voltage protocols where appropriate. Also, in the elderly, consider increasing radiation dosage. For exams with split bolus protocol, consider converting to a single bolus and instead using repeated imaging of the target area to include the phases of interest.
==Example==
