Guidelines for Intravenous Iodinated Contrast Administration in Outpatients Computed Tomography Examinations

A.  Background: Reducing Risk of Contrast-induced Nephropathy (CIN)

The decision to administer contrast in patients undergoing CT should always be a matter of clinical judgment, based on the individual circumstances of the patient and following consultation between the radiologist and requesting provider. Patients with chronic kidney disease (CKD) are at risk of contrast-induced nephropathy (CIN), an uncommon but potentially serious form of acute kidney injury defined by an increase in serum creatinine by more than 25% within 3 days of intravascular administration of contrast in the absence of an alternative etiology. The most important risk factor for CIN is renal insufficiency.  The method of contrast delivery is also important; the incidence of CIN is higher after intra-arterial contrast administration than after intravenous contrast administration. Other medical risk factors for occult renal insufficiency have been established through published data and expert opinion as age > 60 years, diabetes mellitus, prior kidney surgery, other kidney disorders, and hypertension requiring medical therapy.

There are several options to reduce the incidence of CIN in patients with CKD who require contrast-enhanced CT, among them avoiding contrast entirely when it is not required to establish the diagnosis or when another imaging modality may be used to answer a clinical question, increasing the time between contrast-enhanced examinations, and decreasing the total volume of contrast administered. In patients with CKD, peri-procedural volume expansion therapy (oral or IV hydration) is also a well-established method to reduce the risk of CIN. The ideal infusion rate and volume is unknown, but isotonic fluids are preferred (Lactated Ringer’s or 0.9% normal saline). One possible protocol would be 0.9% saline at 100 mL/hr, beginning 6 to 12 hours before and continuing 4 to 12 hours after, but this is only practical in the inpatient setting. Oral hydration has also been utilized, but with less demonstrated effectiveness. For these reasons, the UCSF Department of Radiology employs a practical but conservative approach to screening and volume expansion based on published incidence rates for CIN, described in further detail below.

B.  Screening Patients for Chronic Kidney Disease

The UCSF Department of Radiology routinely screens outpatients undergoing CT examinations to identify those individuals with CKD and thus at potential risk of CIN and uses volume expansion therapy (oral or IV hydration) to mitigate the risk in this subgroup. Patients in whom IV contrast is indicated are screened for known or possible CKD by asking four questions:

  1. What is your current age?
  2. Do you have diabetes?
  3. Do you have hypertension requiring medication?
  4. Do you have ANY problems with your kidneys (such as transplant, single kidney, kidney cancer, kidney surgery, dialysis)?
  • If patient is less than 60 years of age and answers NO to questions 2-4, IV contrast will be administered.
  • If a patient is older than 60 years of age and/or answers YES to any of these questions, an assessment of renal function should be performed before administering IV contrast.

C.  Assessment of Renal Function in Patients with CKD and/or CIN Risk Factors

Estimated Glomerular Filtration Rate (eGFR) is calculated using the patient’s latest serum creatinine, documented within the past 6 weeks. In those patients who have known CKD or other risk factors for CIN as noted above, the referring provider should place a new order for serum creatinine at the time the examination is ordered if the most recent creatinine will be greater than 6 weeks old on the date of the examination. Other patients will have point-of-care creatinine values drawn at the time of the examination using the i-STAT® system.

For consistency, eGFR calculation should be based on the CKD-EPI referenced creatinine method, and requires the creatinine level (mg/dL), age, race (African American versus other) and gender of the patient. An online calculator for eGFR with this formula can be found on the Internet at the following link to the National Kidney Foundation:

https://www.kidney.org/professionals/KDOQI/gfr_calculator

D.  UCSF Guidelines for Contrast Administration and Volume Expansion Therapy

 ESTIMATED GFR (ml/min/1.73 m2)

Guidelines for Contrast Administration and Hydration

≥30

Low risk.  At the current time, there is very little evidence that IV iodinated contrast material is an independent risk factor for AKI in patients with eGFR >30 mL/min/1.73m2.

<30

Higher risk.  The incidence of AKI in patients with eGFR less than 30 has been shown to be as low as 0% up to 10% in large cohorts.  Contrast should be administered cautiously unless the patient is on dialysis and anuric.  If contrast is considered diagnostically imperative and the benefits of contrast outweigh the risk of AKI. The referring attending physician should document the need for contrast and that the benefit of contrast outweighs the risk of AKI in the patient’s medical record. Pre-procedural protection again AKI, if any, will be determined on a case-by-case basis after consultation with the attending radiologist.

References

  1. ACR Manual on Contrast Media, ACR Manual on Contrast Media – Version 10.1, 2015.
  2. Hiremath S, Akbari A, Shabana W, et al. Prevention of contrast-induced acute kidney injury: is simple oral hydration similar to intravenous? A systematic review of the evidence. PLoS ONE 2013; 8: e60009.
  3. Kim SM, Cha RH, Lee JP, et al. Incidence and outcomes of contrast-induced nephropathy after computed tomography in patients with CKD: a quality improvement report. Am J Kidney Dis 2010; 55:1018-25.
  4. Morcos SK, Thomsen HS, Webb JAW, et al. Contrast- media-induced nephrotoxicity: a consensus report. Eur Radiol 1999; 9: 1602–13.
  5. Solomon RJ, Natarajan MK, Doucet S, et al. Cardiac Angiography in Renally Impaired Patients (CARE) study: a randomized 
double-blind trial of contrast-induced nephropathy in patients with chronic kidney disease. Circulation 2007; 115:3189-96.
  6. Stacul F, van der Molen AJ, Reimer P, et al. Contrast-induced nephropathy: updated ESUR contrast media safety committee guidelines. Eur Radiol 2011; 21: 2527-41.
  7. Taylor AJ, Hotchkiss D, Morse RW, McCabe J. PREPARED: Preparation for Angiography in Renal Dysfunction: a randomized 
trial of inpatient vs outpatient hydration protocols for cardiac catheterization in mild-to-moderate renal dysfunction. Chest 
1998; 114:1570-74.
  8. Weisbord SD, Palevsky PM. Prevention of contrast-induced nephropathy with volume expansion. Clin J Am Soc Nephrol 
2008; 3:273-80.
  9. Weisbord SD, Mor MK, Resnick AL, et al. Incidence and outcomes of contrast-induced AKI following computed tomography. Clin J Am Soc Nephrol 2008; 3:1274-81.      

(last revised 3/14/16)