Welcome to this episode of KD Go Conversations and Nephrology. This episode, titled CKD Evaluation and Measurement, is provided by KD Go and is supported by an independent educational grant from AstraZeneca. Here's your host, Doctor Peter Lynn. Hello and welcome to KD Go Conversations and Nephrology. I'm Doctor Peter Lynn, director of the K Heart Research Center.
And family physician in Toronto, Canada and joining me today to discuss the importance of CKD evaluation and measurement is Doctor Madelina Madeiro. Dr. Madeiro is the Head of Nephrology Division at the National Heart Institute in Mexico City and her clinical and research interests include CKD Progression, chronic chemodialysis and CKD of unknown origin. Welcome Doctor Madeiro to the program. Thank you, Doctor Lane, and thank you, Katie. Go.
It's an honor for me to be here today with you. It's really good to have you here and I think the CKD of unknown origin makes you sound like a UFO hunter. So it's kind of interesting to hear that term. But today I guess we're going to focus in on trying to detect kidney disease. I must admit our kidneys work very hard for us and they never complain and by the time they complain, they are quite damaged. So therefore we have to go looking for this damage.
So can you just go over what are the tools that we can use to look for chronic kidney disease? Thank you, Doctor Lynn, that's a great question and you are absolutely right. Kidneys do not hurt until very late stage. So we have some tools to assess kidney function in the earlier stages and these tools are EGFR. So this is estimated glomerular filtration rate and albuminuria and these both are critical to detect and to risk stratify chronic kidney disease.
We know that lower estimated GFR and higher albuminuria are both strongly associated with risk of cardiovascular events, kidney failure and mortality. So their measurement is crucial for effective risk stratification of persons with chronic kidney disease. The presence and severity of algumineuria also guides the use and dosage of treatments that we know delay chronic kidney cyst progression, so such as ACE inhibitors, ARB and SGLT 2 inhibitors.
So the ideal screening and diagnosis approach would consist of a triple marker panel with serum creatinine serum cystatin C. And urine albumin to creatinine ratio. We usually prefer albumin uria over proteinuria. However, we know that in resource limited settings we can also use proteinuria for detection of a protein or albumin in the urine.
There are now equations such as CKD EPI that are used to estimate GFR from markers such as creatinine and sistatin C and the combination of both creatinine and sistatin C. And the latest equation is without inclusion of a coefficient for black rays. So we have these very useful equations that can either use the statin C creating or both. And you know the fact that rays was removed. It's a very important. Event in the nephrology
practice. This was all done due to the concerns about continuing use of race in GFR and led to the removal of the race coefficient. So a big rationale for CKD screening is the availability of many effective interventions to delay CKD progression and that reduce cardiovascular risk. Yeah, that's actually very interesting, The fact that you're talking about renal risk as well as cardiovascular risks. Really having these measurements would be helpful for us to
manage our patients. And as you were saying, you know, serum creatinine, we can get and with the equations, then we can estimate the glomerical for attrition rate. And so that tells us about how to use other medications, how well the kidneys are functioning. And often times I, you know, for simplicity sake, I tell my patients that's the speed of your kidneys that it's working at. And I usually tell them we want at least 60 miles an hour or higher.
And you're only at 30 miles an hour and they seem to understand that concept of speed. And as you were putting it, the urine, albumin, creatinine ratio is very important as well because I tell patients it's a quality of your kidneys. In other words, we want to keep the good stuff in which in our case, we've had that as albumin as being good things to keep in your body. And creatinine, which is waste product as you were mentioning, we want to get rid of that.
And so therefore we want to make sure that the kidney is getting rid of garbage and keeping in the good stuff. So that measures the quality. Of the kidney. So I think that part maybe we haven't explained that so well to patients. Do you find that people may be doing serum creatinines and and maybe not the albumin creatinine ratio? Yeah, that's that's a very good analogy, Doctor Lynn. And you're right.
I mean, people do measure creatinine for the most part, and many labs have automated each GFRS, but I find that a lot of people and are not having their urine albumines checked. And you know this is very important because it is a big risk factor for outcomes such as kidney disease progression and cardiovascular events. And we know that our patients with kidney disease have an even higher risk of dying from cardiovascular causes and reaching to kidney failure.
So both markers are very important in the evaluation of chronic kidney disease. And that makes a lot of sense, so I must admit. In the beginning we only focused on creatinine and then we had the lesions, so we only focused on that. But the album and creatinine ratio together gives extra information, so we need both pieces. So let's say we now have an abnormal test. You've identified a patient. How do we go about finding out the cause of the CKD?
Cuz I think a lot of us just assume it's diabetes or hypertension, but how do you go about thinking about the different causes that would put a patient in a CKD position? Thank you, Doctor Lynn. That's a very important question. It's not everything diabetes or hypertension. So when we evaluate a patient with known or suspected chronic kidney disease, clinicians should inquire about additional symptoms that might suggest a
systemic cause. For instance, if a patient has hemoptysis or a rash or lymphadenopathy or hearing loss or neuropathy, this may Orient us towards something either genetic or towards Glumerlar disease. If a patient has for instance, urinary hesitancy, urgency or frequency or incomplete bladder emptying, then this may guide us
towards urinary obstruction. Moreover, patients should be assessed for risk factors of kidney disease and this include potential nephrotoxins such as non steroidal and inflammatory medications, phosphate based bowel preparations, herbal remedies such as those containing aristologic acid. Antibiotic therapies such as gentamizing and chemotherapies. Also a history of kidney stones or recurrent urinary tract infections may guide us towards the cause.
Of course, as we mentioned earlier, presence of comorbidities such as hypertension, diabetes or autoimmune diseases may lead us towards the cause of the kidney disease. And family history of kidney
disease is important. There are times where we need to do genetic testing, for instance in younger people with polycystic kidney disease where they still do not have cysts, or with inherited forms of focal segmental glomerular sclerosis as this may allow an earlier treatment or make us take decisions such as a big decision on a family member that may be a kidney donor, for instance. Finally, imaging.
Studies such as an ultrasound give us an idea of the chronicity of the disease and helps us to rule out obstruction. And then when we have done all these, a lot of the times we still do not know the cause and we need to perform a kidney biopsy, for instance, in a patient that has albuminuria or hematuria and we are not 100% sure of the cause, then it is important. To have a kidney biopsy as with the histologic diagnosis, we're going to have a more precise diagnosis and a better
management. A fundamental justification for the early detection of CKD is that we now have a lot of available evidence based interventions to slow chronic kidney disease progression as I mentioned earlier and this would help us reduce its complication accurate diagnosis and staging of CKD impact the choice of the treatments. And this is one of the most important causes to establish what's really generating or causing the kidney disease in
our patients. For those just tuning in, you're listening to KD Co Conversations in Nephrology. I'm Doctor Peter Lynn. And speaking with me today is Doctor Magdalena Madero. We're discussing the importance of CKD evaluation and measurement. Yeah, you make a very good point. So now that we've identified a patient with CKD, finding the cause will then direct our therapies and also risk stratify
the patient. So finding the cause is actually as important as detecting the disease in the 1st place of course. And and yet many of us may just say, oh, the EGFR is a little bit low and then we stop there. So all of these lists of diseases that you just mentioned reminds us that there are many causes that can bring a patient to that state of chronic kidney disease. So let's say we have these tests now. And let's say we've got a cause as well. So we know which cause is causing the CKD.
Then when do we consider it as CKD progression? Because a lot of times a nephrologist and the referral centers would say if the CKD progresses, then please refer to us. So what does that mean in terms of CKD progression? Yeah. So that's a very good question, Dr. Lean. And this is something we have debated as nephrologist over years. Progression can be defined in
many ways. It can be defined as a sustained drop in e.g. Fr for longer than three months and a 25% or greater decrease in e.g. Fr from baseline. Rapid progression, for instance, is usually defined as more than 5ML minute loss. In 12 months, there are also slopes of EGFR decline that have been accepted as a definition, such as 30 or 40% decline in
EGFR, let's say at two years. Because, you know, I have to admit that in the past we used to define progression as doubling of the creatinine or kidney failure, but these events are very. Drastic and you don't want to wait until this happens to define progression, and that's why we have been establishing other definitions of CKD
progression. There's also regression and regression can be defined as a sustained higher e.g. Fr category for longer than three months and a 25% or greater increase in the e.g. Fr from baseline. So this means that not everything is progression. Patients can actually get better from the disease. And this would be considered as a regression.
Progression is important because it can help us guide the frequency of monitoring or assess a treatment progress, and This is why we need to establish a progression. Yeah, that's actually a very good point. In other words, the direction, the speed at which it's dropping, those are all very useful information. And to your point is that it changes how quickly we refer, how often we assess them and review their testing. So these are all important things for us to do.
Now you had mentioned something about systatin C and that caught my attention because I'm not sure if everybody is aware of systatin C So when would systatin C be appropriate testing? So in other words, when would our traditional creatinine egfr estimates sort of not be as accurate and what kind of scenarios would we say that a systatin C would probably do better in assessing real function? Thank you. That's a great question. Ideally, cystatin C should be
used for the initial diagnosis. The use of cystatin C alone or in combination with creatinine strengthens the association between the EGFR and the risk of death and kidney failure across. Diverse population. So number one, it better categorizes risk #2. It should be used when the
diagnosis of CKD is uncertain. For instance, patient that has G3AA1, so patient with mild CKD and no albuminuria #3 when muscle mass is low, such as in the case of amputations, or the opposite when there's a large muscle mass, such as observing football players or bodybuilders. Where creatinine may be under or over express and this would over
or underestimate estimated GFR. And finally, a more accurate estimation of e.g. Fr is required a lot of the times for dosing on certain antibiotics such as chemotherapy assessment of kidney function in kidney donors for instance. So therefore there would be certain situations where systatin C is better and I guess as you were pointing out that creatinine is muscle breakdown. So therefore if there's changes in muscle mass, that might affect it as well.
And so there are situations where our creatinine friend may not be as accurate. And that's why systatin C which is sort of reduced at a regular rate in the cells and it's mainly filtered out and there's no secretion of it in the renal area that basically that might give a better measurement and you listed some very important times. Where we need a more accurate measurement and that's where the
systatin C would be useful. And I think that's very useful for us to know because many of us may not have heard of systatin C as the new way of staying for real function. So I think that brings us to a close for this particular session. I want to thank you very much, Dr. Maduro, for your insights into the importance of CKD evaluation and measurement. You nicely told us about the EGFR and how that sort of measures the speed of kidney function. That's one component of it.
Albumin creatinine ratio is another important component. Of assessing renal function. And so therefore both of them together would tell us about the speed of the kidney as well as the quality as I sort of Simply put it for my patients. And then you talked a little bit about cyst and C and it's important role in certain circumstances or maybe the creatinine may not be estimating the glomeris filtration rate as
well. And also to identify the causes of CKD because you listed all these causes that would have very different treatments and different trajectories. And they would need different strategies to make sure that we can prevent the kidney progression. And then you nicely told us about kidney progression and what we should be looking for deterioration, the e.g. Fr changing classes of CKD and also this rapid drop of five mils per minute over a 12 month period.
So we have things that we can look out for. So that way we can make sure that the patient gets the care in a timely fashion. And I think all of this, I'm hoping with your knowledge and insight will help us all make sure that we can detect CKD. And make sure that we manage these patients as well as we can so that we can avoid those complications that you were saying used to be the only thing we measure which was doubling of creatinine and end stage disease
dialysis. Hopefully we will avoid those horrible things for our patients by diagnosing them earlier and making sure that they do well. So thank you very much Doctor Madeira for your insights and all your hard work in terms of treating patients and sort of getting the benefits of all this knowledge make sure that the patients will benefit from this new. Treatment strategy and detection. Thank you, Dr. Lin, for all these very important and interesting questions.
You just gave a very nice summary of what we have discussed and it has been an honor to share this forum with you. Great pleasure with you. And it's so easy to summarize when you put things beautifully. So thanks very much again. Thank you. You've been listening to KD Co Conversations and Nephrology. You can find more@kdco.org/podcast. Thanks for listening.