Question

write a paragraph regarding these topics

5. appropriateness of contrast media to exam c. laboratory values (e.g. BUN, Creatinine, GFR)

Answer 1

Ans) Historically serum creatinine was the lab value used to assess kidney function. A better and more accurate measure is a lab result called estimated glomerular filtration rate (eGFR). eGFR takes into account the serum creatinine value and also patient age, race and gender which affect kidney function results. At UCSF we use this very accurate blood test to assess kidney function and it can be obtained quickly, right before a scan.

- For CT, eGFR > 45 indicates no increased risk of kidney damage from contrast material. eGFR > 30, but less than 45 indicates that while it is safe to get contrast material, there is a small risk of causing kidney damage. In that situation, we will inject additional fluid into the patient’s vein before and after the contrast material injection. This hydration is effective to prevent any renal damage. For MRI, it is safe to give a regular dose of contrast material as long as the patient’s eGFR is > 30.

- For both MRI and CT contrast agents, once injected they are cleared from your body by your kidneys. If your kidney function is below normal then two things happen. First, the contrast agents are cleared more slowly from your body. If kidney function is very poor (eGFR < 30) this prolonged exposure can lead to a change in the injected MRI agent’s chemical composition and create a small risk of developing NSF. For MRI contrast agents there is no risk of developing the skin disease of concern if the eGFR is >30. For CT contrast materials, where a larger volume of the contrast agent is used than for MRI, the functioning kidney is exposed to contrast material for a longer time than in people who have completely normal kidneys and can clear it more rapidly. This prolonged exposure is thought to increase the risk of developing kidney damage. The risk is very low, about 1% unless the patient’s eGFR is < 30, then the risk goes up slightly. Even when kidney damage occurs, it is almost always temporary and will resolve without treatment.