The American College of Radiology updated its Manual On Contrast Media in 2021. A few key statements are relevant to our practice in the emergency department. They are reproduced here in question and answer format for simplicity.
1) Is contrast induced acute kidney injury a real entity? Yes, but rare.
“At the current time, it is the position of ACR Committee on Drugs and Contrast Media that CI-AKI is a real, albeit rare, entity. Published studies on CI-AKI have been heavily contaminated by bias and conflation. Future investigations building on recent methodological advancements, are necessary to clarify the incidence and significance of this disease”
Ch 10, pg 33, Nov 9, 2021
2) Is creatinine elevation after contrast use sufficient to make a diagnosis of contrast induced acute kidney injury? No
“Elevations in serum creatinine are neither sensitive nor specific for individual types of AKI. Any serum creatinine-based criteria, used in isolation, will be unable to separate CI-AKI (contrast induced acute kidney injury) from generic CA-AKI (contrast associated acute kidney injury) . This applies to scientific studies lacking appropriate control groups and to clinical evaluations of individual patients”
Ch 10, pg 34, Nov 9, 2021
3) What is the difference between contrast associated and contrast induced acute kidney injury?
“Contrast-associated acute kidney injury (CA-AKI) (formerly known as post-contrast acute kidney injury (PCAKI)) is a general term used to describe a sudden deterioration in renal function that occurs within 48 hours following the intravascular administration of iodinated contrast medium. CA-AKI may occur regardless of whether the contrast medium was the cause of the deterioration. CA-AKI is a correlative diagnosis.
Contrast-induced acute kidney injury (CI-AKI) (formerly known as contrast-induced nephropathy (CIN) is a specific term used to describe a sudden deterioration in renal function that is caused by the intravascular administration of iodinated contrast medium; therefore, CI-AKI is a subgroup of CA-AKI. CI-AKI is a causative diagnosis.”
Ch 10, pg33, Nov 9, 2021
4) What criteria is recommended to define acute kidney injury?
“The diagnosis of AKI is made according to the KDIGO (2012 Kidney Disease: Improving Global Outcomes Clinical Practice Guidelines) criteria if one of the following occurs within 48 hours after a nephrotoxic event (e.g., intravascular iodinated contrast medium exposure):
- Absolute serum creatinine increase ≥0.3 mg/dL (>26.4 µmol/L).
- A percentage increase in serum creatinine ≥ 50% (≥1.5-fold above baseline).
- Urine output reduced to ≤ 0.5 mL/kg/hour for at least 6 hours.
This system has been advocated as a common definition of intrinsic acute kidney injury, regardless of etiology. Therefore, it can be used to define the parameters of CA-AKI as well as CI-AKI. The KDIGO criteria also outline a system for staging the degree of renal injury that is present following the diagnosis of AKI; the interested reader is referred to the original manuscript.”
Ch 10, pg 34, Nov 9, 2021
5) Is it necessary to screen all patients for creatinine level prior to use of intravenous contrast ? No
“The following is a suggested list of risk factors that may warrant renal function assessment (e.g., serum creatinine, eGFR) prior to the administration of intravascular iodinated contrast medium. This list should not be considered definitive and represents a blend of published data and expert opinion:
- Personal history of renal disease, including:
- Known chronic kidney disease (CKD)
- Remote history of AKI
- Kidney surgery
- Kidney ablation
- History of diabetes mellitus (optional)
- Metformin or metformin-containing drug combinations
Patients who are scheduled for a routine intravascular study but do not have one of the above risk factors do not require a baseline serum creatinine determination before iodinated contrast medium administration.”
Ch 10, pg 36-37, Nov 9, 2021
6) What is the typical clinical course of patients who experience acute kidney injury after contrast injection ?
“The clinical course of CA-AKI (and, presumably, CI-AKI) depends on baseline renal function, coexisting risk factors, degree of hydration, and other factors. However, the usual course consists of a transient asymptomatic elevation in serum creatinine. Serum creatinine usually begins to rise within 24 hours of intravascular iodinated contrast medium administration, peaks within 4 days, and often returns to baseline within 7 to 10 days. It is unusual for patients to develop permanent renal dysfunction”
Ch 10, pg 37, Nov 9, 2021
7) Can dialysis patients receive intravenous contrast ? Yes
“Patients with anuric end-stage chronic kidney disease who do not have a functioning transplant can receive intravascular iodinated contrast medium without risk of further renal damage because their kidneys are no longer functioning. However, there is a theoretical risk of converting an oliguric patient on dialysis to an anuric patient on dialysis by exposing him or her to intravascular iodinated contrast medium. This remains speculative, as there are no conclusive outcomes data in this setting. Therefore, patients undergoing dialysis who make more than 1-2 cups of urine/day (100 mL) should be considered nonanuric and treated as high-risk patients similar to patients with AKI or eGFR less than 30 mL/min/1.73m2 who are not undergoing hemodialysis.”
Ch 10, pg 39, Nov 9, 2021
8) Do end-stage renal patients need urgent dialysis after a CT scan with IV contrast? No
“Patients should not have acute dialysis nor continuous renal replacement therapy initiated or alter their schedule solely based on iodinated contrast media administration regardless of renal function due to the risks, costs and lack of benefit.”
Ch 10, pg 39, Nov 9, 2021
9) Is there a patient population in which intravenous contrast is absolutely contraindicated? No
“Concern for the development of CI-AKI is a relative but not absolute contraindication to the administration of intravascular iodinated contrast medium in at-risk patients that have AKI or an eGFR less than 30 mL/min/1.73 m2 and are not undergoing maintenance dialysis… In some clinical situations, the use of intravascular iodinated contrast medium may be necessary regardless of CI-AKI risk. Although there is data suggesting a directly proportional dose-toxicity relationship for intracardiac iodinated contrast medium, there is no analogous robust data for intravenous iodinated contrast media within the range of clinically administered doses. Therefore, it is not recommended to reduce doses to attempt to mitigate the risk of CI-AKI as this may result in suboptimal or nondiagnostic images. Instead, standard contrast dosing is recommended if the benefits have been deemed to outweigh the risks for intravenous iodinated contrast media administration in high-risk patients for CI-AKI”
Ch 10, pg 37-38, Nov 9, 2021
10) Is it necessary to avoid repeat doses of intravenous contrast within 24 hours? No
“One purported risk factor for the development of CI-AKI is the administration of multiple doses of intravascular iodinated contrast medium within a short period of time. Most low-osmolality iodinated contrast media have a half-life of approximately two hours. Therefore, it takes approximately 20 hours for one administered dose of contrast medium to be eliminated in a patient with normal renal function. Therefore, it has long been suggested that dosing intervals shorter than 24 hours be avoided except in urgent situations. We do not believe that there is sufficient evidence to specifically endorse the decision to withhold a repeat contrast medium injection until more than 24 hours have passed since the prior injection, nor to recommend a specific threshold of contrast medium volume beyond which additional contrast media should not be given within a 24-hour period. Further, obtaining a serum creatinine measurement between two closely spaced iodinated contrast medium enhanced studies are unlikely to be of any benefit given the slow nature of change of serum creatinine in patients with AKI. Therefore, the decision to administer closely spaced contrast-enhanced studies is clinical and subjective, with high risk patients (e.g., Stage IV and Stage V chronic kidney disease, AKI) treated with greater caution than the general population.”
Ch 10, pg 38, Nov 9, 2021
For further reading, here are more resources from the EB Medicine library: