Creatinine testing prior to gadolinium MRI administration

Laboratory results should be checked for the most recent serum creatinine on ALL patients (by the technologist performing the study). For patients with the following risk factors, serum creatinine with calculation of eGFR should be performed within 6 weeks of the MRI study:

• Age over 60 years
• History of “kidney disease” as an adult, including tumor and transplant
• Family history of kidney failure or disease
• Diabetes treated with insulin or other prescribed medications
• Hypertension (high blood pressure) requiring medication
• Multiple myeloma
• Solid organ transplant
• History of severe hepatic disease/liver transplant/pending liver transplant. For patients in this category only, it is recommended that the patient's GFR assessment be nearly contemporaneous with the MR examination for which the gadolinium is to be administered.

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Routine creatinine testing prior to contrast administration is NOT necessary in all patients^1,2. With the exception of age and hypertension (see below), the indications for creatinine testing in the above guidelines are those suggested by the ACR¹. However, these recommendations should be considered in the light of several confounding factors:

1. In a study of 2034 outpatients who all had routine creatinine testing prior to outpatient CT, 66 patients had a creatinine of 2.0 or above². All but 2 of the 66 had one or more of 8 risk factors that were chosen based on published literature (history of renal insufficiency or renal disease, diabetes mellitus, advanced age, male gender, nephrotoxic-drug use, chemotherapy, HIV/AIDS, solitary kidney). The two cases that would have been “missed” by a policy of selective creatinine testing had a creatinine of 2.0 and 2.2. Two particularly notable findings in this study were that age alone was not an important risk factor, and that both insulin-dependent diabetes mellitus and non-insulin-dependent diabetes were important risk factors.
2. The use of age as a risk factor and the choice of threshold are both controversial, with conflicting data in the literature. Community based studies of serum creatinine suggest age, hypertension, and diabetes are important predictors of creatinine elevation^3-5. In addition, many centers use age (with variable thresholds) to determine the need for creatinine testing and this practice is also engrained in the department culture at UCSF.
3. Standard practice is variable and often based on little to no evidence¹⁵. For example, there is little data on whether in-patients are substantively different to outpatients.
4. Arguably, the list of medications should be expanded to include chemotherapy, since many of these drugs are nephrotoxic¹⁶.
5. In general, these guidelines are simply guidelines, and strict adherence in every case may not be in the patient's best interest. Physician discretion and judgment are paramount, and commonsense should be applied to individual patient's circumstances.  Conversely, it may be prudent to check creatinine in a sick debilitated patient even if they do not have any of the specific factors listed above.

Key point: Routine creatinine testing prior to contrast administration is NOT necessary in all patients; the major indications are age over 60, history of preexistent renal insufficiency, diabetes mellitus, or hypertension.