Contrast Protocol

 

Contrast Protocol

How do you decide whether to draw labs for renal insufficiency? Who receives contrast, what kind, and in what dose? 
gadolinium protocol
 
All documented cases of nephrogenic systemic fibrosis or gadolinium-induced nephropathy have occurred in patients with severe renal impairment, defined as those with estimated glomerular filtration rates (eGFRs) less than 30 mL/min/1.73 m². Identifying these patients prior to administration of contrast is thus highly important.
For inpatients the process is relatively simple, as updated medical histories and laboratory values are usually immediately accessible through charts or the electronic medical record. The American College of Radiology (ACR) recommends that eGFR's be obtained in all inpatients within two days of gadolinium administration. I personally believe this arbitrary 2-day interval needs to be modified in light of the patient's clinical condition (either longer or shorter depending on risk).

For outpatients, direct patient questioning is required. Factors to be considered include known urinary tract disease, surgery, or history of dialysis; advanced patient age (> 60), coexistent systemic diseases associated with impaired renal function (diabetes, hypertension). Our general history screening form also includes questions about medications, cancer, and other systemic diseases. So, if a patient indicates a history of an underlying illness (e.g., multiple myeloma, liver disease) or nephrotoxic drug use (non-steroidal anti-inflammatories, aminoglycosides), our index of suspicion is heightened. The ACR has provided a table of recommended time intervals over which repeat eGFR should be performed in patients with known or suspected renal compromise. For at risk patients in a stable clinical state, an eGFR within 6 weeks is recommended. For patients with known renal insufficiency or potentially unstable state, an eGFR within 1-2 weeks (or even less, depending on clinical circumstance) should be obtained.
When in doubt, draw an eGFR!
The preferred screening test is an an eGFR using the 4-variable Modification of Diet in Renal Disease (MDRD) equation. This takes into account age, race, gender, and serum creatinine. For children, the updated Schwartz equation should be used. These calculated values are provided automatically by most modern laboratory systems.
The protocol we use at Wake Forest is given below. Because of stability and relaxivity considerations, we prefer to use half-dose (0.05 mmol/kg) MultiHance® for patients whose eGFRs are in the range of 30-60 mL/min/1.73 m².
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Even though an option exists on the flow chart for patients GFR<30, it is hard to imagine an extreme enough circumstance where this might apply. Perhaps a patient with life-threatening a spinal epidural abscess whose limits could not be established clearly by noncontrast MRI or myelography? At our large hospital we have not yet encountered such an extreme case over the last 8 years in 100,000+ MR studies we felt justified the risk.

The Modification of Diet in Renal Disease (MDRD) equation is given by the following equation, computed and reported automatically by most laboratory systems:

eGFR (mL/min/1.73 m²) = 175 x (serum creatinine in mg/dl)−1.154 x (age in yrs)−0.203
This value is multiplied by 0.742 if the patient is female and by 1.212 if African American.

The updated Schwartz equation is given by

eGFR (mL/min/1.73 m²) = 0.413 x (height in cm) ÷ (serum creatinine in mg/dl)

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