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Melanie Cole, MS (Host): Welcome to Expert Insights with the Carle Foundation Hospital. I'm Melanie Cole. And today, we're discussing iodinated contrast use and renal disease, an update and new recommendations. Joining me is Dr. Jay Jimenez. He's the Associate Medical Director of Radiology at the Carle Foundation Hospital.

Dr. Jimenez, always a pleasure. Thank you for joining us again. Tell us the current evidence regarding risk of contrast agents in imaging in general, but also in patients with renal disease. What are those risks? How are they assessed? Give us a little update on this.

Dr. Juan Jimenez: Sure. Thank you for having me. The general risks for iodinated contrast really fall into two categories. One of them is related to the potential for an allergic reaction, which we're not really going to talk about here, but that is one of the big risks that we like to screen for and potentially pre-treat for, because it can be life-threatening. The other risk is that of potential renal disease. And, you know, this has been a somewhat controversial topic over the years in terms of the relative risk of contrast-induced nephropathy or acute kidney injury following contrast media administration for CT or other imaging procedures.

To kind of turn back the clock a little bit for 10, 15 years ago, when this really started to come on to everybody's attention, there were a lot of recommendations that came out talking about the risks of a contrast-induced nephropathy. And when we talk about that, when we say that, what this means is it's a degradation of renal function that occurs following the administration of an iodinated contrast material. And so there was a perceived risk associated with this, and there was a lot of emphasis being put on screening patients who were at risk, pre-treating them with various medications and other pretreatment regimens and also maybe withholding the contrast altogether.

So back 10, 15 years ago, we were very conservative in terms of our dealing with contrast-induced nephropathy. We would screen patients very readily who have the risk factors. We had very robust pre treatment regiments, which included hydration, the administration of various medications, such as Mucomyst and that kind of thing.

What we found over the years, there's been an emerging body of evidence that has really called into question whether contrast-induced nephropathy is big of an issue as people once thought it was. And a lot of the original research that was done that led people to think that iodinated contrast was harmful to the kidneys was done on patients who were undergoing cardiac catheterization and the big difference between that procedure and what we do in radiology for most CT examinations is that for cardiac catheterization, the dye load goes into the artery, and so it's immediately being shot into the kidneys. Whereas in CT, when we give IV contrast for a typical CT examination, that's given intravenously. The contrast essentially have to travel a longer way through the body, gets diluted, and the potential damage to the kidneys is actually quite a bit less than what we would have seen in some of those original studies. One of the other factors is that these were patients who were undergoing cardiac catheterization, they had cardiovascular disease, they had risk factors, they were diabetic, they had peripheral vascular disease, they may have had underlying renal insufficiency. So that subset of patients was already preselected to be at very high risk for contrast-induced nephropathy.

As we've progressed, as people have looked more critically at this problem, there's an emerging body of evidence that shows that maybe it's not such a big risk as we once thought it was. There have been studies that have shown that have compared cohorts of patients who were administered IV contrast to those who didn't and they demonstrated the same degradation or rates of degradation of renal function following their CT examinations, whether or not they were given the contrast. So these are the kinds of evidence that we're dealing with now. And as an institution that performs over 300,000 imaging exams a year, you know, we want to be following the best practices and make sure that we're not subjecting our patients to unnecessary testing or unnecessary pre-medication or other mitigation procedures if the risk really isn't there. So that's kind of why we're talking today.

Melanie Cole, MS (Host): Interesting. It really is an interesting topic. And I was reading about contrast-induced nephropathy in my research for this. So, was there evidence? I know you touched on this a little bit, but I'd like you to expand a little bit that pre-treatment in patients reduced any of that risk? What are we doing now? Give us an update on how the risk-benefit discussion takes place, any pre-treatment that's needed or even consents.

Dr. Juan Jimenez: So I think it's really important to talk about what are those risk factors. You know, who are the patients who are at highest risk of developing contrast-induced nephropathy, and what is this group of patients that we need to have these discussions with and potentially pre-treat or hydrate? So if we talk about contrast-induced nephropathy risk factors, this, you know, might include diabetes, advanced age over 60, people with pre-existing renal insufficiency, cardiovascular disease; anybody who's in a dehydrated state, whether it's chronic or acute; short interval between contrast doses, so hospitalized patients who are getting repeat CT scans and repeated contrast dosage, and then also the high contrast volume, so some of our examinations like vascular examinations that we do with CT require slightly higher dose of contrast. So we need to be keeping these things in mind when we're counseling patients and identifying those high-risk patients.

You know, one thing that is worth mentioning is that the safety of the IV contrast agents has changed over the years. So once again, going back many, many years when some of the first studies were done that demonstrated the risk to renal function with IV contrast administration, the chemical nature, the osmolarity of the contrast agent was much higher. And now, with the newer contrast agents, the osmolarity is much more closer to what we see in normal plasma. And that helps mitigate the risk of renal disease when we administer contrast material to these patients.

But, you know, once we've identified the high-risk patients, the next step is these are the people that we need to actually get laboratory data on in a short interval before imaging to truly assess their renal function. Traditionally, this has been done with the serum creatinine level. More recently, we have abandoned that and transitioned to using the estimated GFR, which is typically regarded as a more accurate measure of renal function, particularly for these high-risk patients. Once we do that and we've established a threshold, which we currently use 30 for an eGFR, so anybody with an eEGFR over 30, they can proceed with imaging and contrast administration with no pre-medication, with no other, you know, discussion or mitigation techniques. People who are below 30, that's when we have to kind of take a step back, start having discussions with the ordering clinician in terms of are there alternatives to this examination that don't require the use of iodinated contrast. Maybe we can do this with MRI, which is a different class of contrast agent altogether. Maybe we can forego the imaging or do it without contrast. Or maybe the ordering clinician needs to have a discussion with the patient, with other specialists, such as nephrologists to discuss the risk to the kidneys and determine whether this is a study that we really need to proceed with.

Once we do that, once we've decided that we've got to proceed with the imaging study, there are some measures that we can take. Now, years ago, we used to pre-medicate with an acetylcysteine or Mucomyst. That has largely been abandoned. The American College of Radiology does not find value in that. At this point, we pre-hydrate with intravenous fluids. Here at Carle, we use a lactated Ringer's crystalloid solution. However, normal saline hydration has been found to be every bit as effective. And so the pre-hydration which occurs before the procedure and then for a few hours afterwards is considered sort of the best practice, if you will, in terms of helping to prevent contrast-induced nephropathy in those patients who are considered to be at higher risk of developing it.

Melanie Cole, MS (Host): You didn't mention dialysis patients. Where do they fit into this picture?

Dr. Juan Jimenez: Well, so people who already have end-stage renal disease who are on dialysis, they don't really fall into this, you know, because, you know, their kidneys are already damaged. They're already on dialysis. So with a dialysis patient, for instance, we try to time their dialysis treatment shortly after the contrast administration, so that it's not sitting in there for too long.

Melanie Cole, MS (Host): I'm glad you mentioned that. I was going to ask you if it's supposed to be immediately following the administration. So thank you for clarifying that. And now, who is qualified in this case? Sometimes there's not always a radiologist in the room or in this case, and those risk factors is there. Who is then qualified and are there guidelines?

Dr. Juan Jimenez: The actual contrast is administered by our imaging technologist under the guidance of our radiologist. So, we have to have a radiologist more or less available, you know, in the hospital, but then our imaging technologist actually administer the contrast to the patient as part of the examination.

Melanie Cole, MS (Host): What are your final thoughts and any updates or new recommendations that you'd like to offer for other providers on iodinated contrast use and renal disease?

Dr. Juan Jimenez: Well, I think, you know, in closing, given the controversies that have emerged recently over, you know, the true risk of contrast-induced nephropathy, you know, I think more research needs to be done. There is an emerging body of evidence that shows that we can probably relax some of the restrictions that we previously had in place which is a good thing, because there were people who were being withheld contrast and unnecessary testing being done, which we, as an organization at Carle have taken steps to reduce that. So we have lowered our threshold to eGFR of 30, which is considered in line with what the evidence is showing as those are the patients that are at the highest risk of developing contrast-induced nephropathy. You know, even though it is controversial, we still need to proceed as if contrast-induced nephropathy is a real entity and that these patients who are at high-risk we do need to treat them differently and we do need to make sure that they are protected.

But as in everything in medicine, the decision to test or have a procedure, it really always should boil down to a risk-benefit discussion. And I try to avoid, you know, developing procedures and protocols that paint a line in the sand and say, "These people can never have this," because, you know, CT has become such a ubiquitous part of working up patients, particularly in the acute care setting. And when you think about the people who come to our emergency department with potentially life-threatening issues like pulmonary emboli, or have had trauma and need to have their vascular systems imaged, you know, that becomes a risk-benefit analysis. And with the risk of contrast-induced nephropathy being relatively small, you know, my feeling would be that the information that we can gather by doing the contrast-enhanced study far outweighs any risk that we might have. So again, it's the radiologist, it's the ordering clinician, it's the other specialists that really need to collaborate, have these risk-benefit discussions and come to an informed decision, hopefully with the patient's input on whether to proceed or not.

Melanie Cole, MS (Host): Thank you so much, Dr. Jimenez. You are such a great guest as always, and really a great educator. Thank you so much for joining us. For more information and to get connected with one of our providers, you can always visit carle.org or for a listing of Carle. And to view Carle-sponsored educational activities, please visit our website at carleconnect.com.

That concludes this episode of Expert Insights with the Carle Foundation Hospital. I'm Melanie Cole.