In this talk, we address a common misunderstanding: a “low kidney function” value on a lab report does not automatically mean kidney disease. Lab results are snapshots in time, and they reflect only one aspect of kidney function, while the kidneys themselves are far more complex organs. Focusing on numbers alone can easily lead to the wrong conclusions—and unnecessary worry.
The video explains how to interpret lab results in the context of real clinical status and the full medical picture: why the goal of nephrology is not simply to “improve lab values,” why a treatment that temporarily lowers filtration can sometimes be beneficial, and why drinking more water is not a solution by itself. If you would like a clearer understanding of what the numbers truly mean—and what they don’t—it’s worth watching the video or reading the transcript.
The content of the video in written form
Hello, this is Dr. Zsom.
Dear patients, when you are referred to the nephrology clinic, it’s often on the basis of some lab work. We need to understand what this lab work means, and we need to see first that any diagnosis made through lab work alone is always uncertain and needs confirmation. Low kidney function does not equal kidney disease, because low kidney function may not be permanent and may be a signal reflecting something else—something other than kidney disease. The kidney is not a filter; it’s very important to understand that, partly because kidney function measures only the filtering function of the kidney, yet the kidney is a human organ with very complex functions and a very complex cooperation with the heart and with other organs.
To understand the complexity of this, let’s review how we arrive at lab works reflecting supposedly kidney function. Well, the kidney function from the lab work that forms the basis of your referral to the nephrology clinic is a concept; it’s based on an estimation of an estimation of an estimation, so it’s a pretty shaky concept. It is a crude approximation of filtering capacity, one of the many functions of the human kidney—a function that is very variable in time and it is influenced by things other than kidney disease. So, increasing filtering capacity, that is improving your labs, does not equal treatment of kidney disease; sometimes it is the opposite. And it is very important to understand that, whatever they tell you and whoever says it, drinking fluids does not save you from dialysis. Drinking fluids might be a cosmetic approach to your lab problems, but it does not cure the real problem; it’s not a Holy Grail. And let’s understand this on multiple levels. First of all, multiple scientific studies showed that drinking fluids alone does not affect kidney function unless you are dehydrated. It is logically not the case, and I’m going to describe that in great detail.
So let’s be clear on this: nephrology is not aimed at making your labs look better. It’s not even aimed at improving filtering capacity of your kidney; rather, its objective is to treat the patient with kidney disease, sometimes even by lowering filtering capacity, making your labs temporarily look worse, but stabilizing your kidney and treating the underlying disease. So, wisdom says that a bad doctor is interested in your labs, while a good doctor is interested in you. —
So there is a kind of shyness about philosophy, yet philosophy is always behind medicine and science; it is just it is ignored or it is forgotten. So you do have a philosophy but you deny it; you say, “I don’t like philosophy,” yet you are practicing it. And to show you that this is the case, and this is very relevant to your lab work and how you approach kidney disease, we need to understand the following: how do we determine kidney disease, so do you have it or you don’t? How do we measure kidney function? Are we really good at it? Are we precise? Are we modeling the right thing? How do we identify risk factors for you to get on dialysis or avoid it? How do we integrate lab results? Is it the case that your lab work is universal and absolute and, no matter who you are under what circumstances, it always tells you the truth? How do we conduct research experiments that determine how we treat kidney disease, and how do we make sense of research findings?
So understand, when you believe in your lab results, you assume that you know the answers to all of these questions, or that your doctor knows, or the researcher knows the answers to these questions. Yes, philosophy is there whether we admit it or not; it’s there. We believe in numbers like this, you see, and we believe that we can measure the function of complex systems by simple quantitative measures. In a way, the numbers are holy and the numbers do not lie, and the numbers tell you what the situation is. Well, believing in objectivity, lab results will decide; they are the most important thing because they are black and white. We believe in generalizations: what is true here is also true there; what is true for one patient is also true for the other patient without any further questions asked. Now, is that really the case? You can guess it’s not.
So philosophy matters; uncovering hidden assumptions, we need to understand what we believe in so that we can go forward. We believe we can easily interpret results, yes, but this is a hidden assumption and it may not be true in a specific situation. Measurement is not absolute; snapshot results do depend on specific circumstances. Yes, we believe that, but it’s not true that statistics are infallible. Oh well, any researcher would know that that is not the case and that one individual is not necessarily the same as the ideal average, the imagined mean average of a sample population; in other words, the group of people that you are measuring something in to do research. Now, so are you the ideal average and imaginary average?
Labs are good because they are black and white, so there is no discussion. It’s either normal or it is unnormal. I mean, a three-year-old child can say, “This is normal, this is not normal; this is black, this is white.” This is very good, easy decision even for the most absent-minded doctor. I mean, you either fall into normal or you do not fall in the normal; so you are either positive or you are negative. Easy to control, easy to compare, easy to reproduce as it is based on standard measurements and standard methods. So, all labs do the same thing under the same circumstances, so it’s kind of a universal, absolute result. What is it? It is oversimplified because each individual is identified with an idealized mean. So here you see is a particular result—it’s five or six or seven—and here is how often you get that result, and this is your average; it’s called the mean. And this is a measure of how wide this distribution is; you know, it’s called a standard deviation. And so, two standard deviations from the mean to the right or to the left, that tells you that you fall into normal. So you imagine that this is the truth. What is the truth? The mean, the average? Even if not even one person actually has this result, you call that an idealized average, a simple mathematical average of the population. So you believe that you are here or you should be here, and that is your aim. Idealized sample means versus optimal: what is most common may not be the optimal. What if in the sample population everybody had high cholesterol? Well, do you want to be the average then?
Cross-sectional means that what was normal in the past would be the same because it’s cross-sectional; it ignores time passing. So, you simply do not take into consideration how things change in you; your function, how does it change from day to day? It is a snapshot; in fact, it gives you an instantaneous result. So first of all, what was normal cholesterol for a person in, say, 100 years ago who worked on the field? Just because you measured cholesterol then and you determined what should be normal then, you then think that it’s normal irrespective of the changing circumstances and changing times, right? And in addition to that, you do a snapshot: you draw your blood and then you believe that whatever results you get, you would get the same result the next day and the next day and the next day. And it is not the case in terms of kidney function.
So the ugly thing about this is that we are pretentious, you see. We believe that a complex system such as the kidney can be characterized by a single measure. What about specificity and the unique circumstances? So you may be dehydrated, you may have temporarily a situation where you have diarrhea or some kind of disease, and it’s all a temporary thing and by the next day it goes back to normal. So is an idealized mean some abstract normal in the context of a given individual? While it is not, the judgment of an experienced doctor aware of local conditions and aware of your situation is always the most important thing, and you cannot ignore that.
So the role of the patient in all of this would be to describe your symptoms, provide a brief history, and then let the doctor interpret the result on the basis of your specific situation; otherwise, things can turn pretty ugly. So let’s summarize this part: you are referred to the nephrology clinic because of, on the basis of, some lab work that shows some kind of a problem, but the disease process in an individual is always unique. There are common patterns that you share with other patients, sure, and that makes sample means useful—again, averages—but these must be placed in a context. Yet the patients and sometimes doctors believe that there is an abstract, ideal, normal value for objective measures that tell you something absolute irrespective of your local circumstances and unique conditions. So you ignore the context, and that is the ugly thing.
So to avoid that, let’s go back to everyday looking. In order to understand how to measure kidney function, one must know what the human kidney actually does. So what is kidney function? Well, it’s not just a filter. Can we judge how the kidney is doing simply by measuring its filtering capacity? Well, yes, so far as all kidney functions are affected by a given disease equally, but this is not the case and I’m going to show you examples. So perhaps temporary changes in filtering capacity can be influenced by factors other than kidney disease. Oh yes, so if you have several functions that are affected, then you most likely have a kidney disease; if you only have one function, it’s just a temporary problem and I’m going to show you examples.
So what about identifying risk factors? So what are your risk factors for kidney disease? What are your risk factors that you will end up on dialysis? We need to understand those. Or perhaps there are also risks for other things: what is a risk factor for kidney disease may be a risk factor for life quality, your nutritional status, frailty, muscle mass, cardiovascular disease, and death. So once you establish risk factors, you need risk factors for all these, and there are risk factors like that.
First of all, what does the kidney do? Well, it removes poisons, sure. These poisons, called toxins or uremic toxins, are produced during normal or abnormal metabolism. So they are often produced or converted by the liver or gut bacteria; gut bacteria is otherwise called the microbiome. And especially if these toxins are small, water-soluble, and not very much bound to proteins in the blood, they are then slowly and continuously filtered through the kidney. But this process depends on the blood supply; your kidney must have enough oxygen, a good blood supply. And of course, it also is dependent on the need of the human organism; maybe what is a toxin if there is a lot of it, maybe it’s necessary if there is only a small amount. So this process is closely regulated on multiple levels. Sounds complicated, but it is.
The kidney is very adaptable; the kidney can identify what your body needs and adapts. So the kidney is able to retain salt and fluid if it’s necessary or remove a large amount if that is necessary. So the kidney is a very adaptable organ; it has a very complex function, and it is able to adapt through multiple mechanisms. The kidney is a miracle. So if your kidney does not get enough fuel—and usually we are talking about oxygen here through blood supply, of course—then the kidney cannot filter and all the other functions will be also affected, but especially the filtering function.
So if you have dehydration, for example, because of diarrhea or you just don’t eat as much because maybe you have loss of appetite—remember, when we are talking about dehydration, it’s a misnomer, isn’t it? Then we think about not enough fluids, yet what the kidney needs is a ratio of salt and fluid, with both salt and fluid. So when you are dehydrated, you need both fluid and salt. If you have heart failure, you don’t get enough oxygen, or if you have blocked arteries (atherosclerosis), you have a low blood pressure. Very important: if you have low blood pressure, the kidney cannot filter. If you have a severe infection, you have advanced lung or liver disease, or you take some anti-inflammatory medications like ibuprofen or others because you have a sore knee or something like that, in all these situations the kidney cannot filter because it does not get enough oxygen. So in all these situations, you don’t need kidney disease for the filtering capacity to go down. Right? So if you do lab works in a situation like this and you don’t have kidney disease, yet your kidney function goes down.
But the kidney does other things that are not necessarily connected with the filter. It is able to regulate salt and fluid volume. So it actually is not true that the more urine you have, the more you remove the poisons. That is not true; the salt and fluid regulation is largely independent of toxin removal. Now it’s important to understand that the kidney is able to remove salt and fluid all the way while maintaining the appropriate ratio of salt and water in the blood. So the ratio is very important; it’s called sodium concentration in the blood. So the kidney is instrumental in maintaining the appropriate sodium concentration.
If you happen to live in the desert like this person here, you may lose as much as 11 liters of water, and the kidney is trying to adapt to this situation by reabsorbing water. So you are able to remove toxins to some extent at least, even in a very small amount of urine, because you need the water and the kidney reabsorbs it. So the family doctor may or may not know this; so the family doctor is going to tell you to drink a lot of fluids even if you are not in the desert.
Miraculous! So the most important thing is that there is salt and water regulation and there is filtering capacity, and the two things are not the same. So if you drink a lot of fluids, yes, that might improve your lab values because it dilutes not only sodium concentration but also toxin concentration, but that does not mean that your kidney is better.
So what happened in the past? Well, it happened in the past that sodium-to-water ratio has always been important, and historically, sodium and water ratio is very close to the sodium concentration found in seawater. If sodium concentration is low, it does not necessarily mean that you have a low amount of sodium in the body; it just means that you might have too much water instead. And then the treatment is going to be different. So the concentration of sodium is closely regulated; it is kept close to the sodium concentration in seawater. And so whenever you have excess water, the water is going to be removed by the kidneys without a change in your toxin removal. So the poisons are going to be removed from the body irrespective of how much volume your urine has, how much water your urine has. Potassium, phosphorus, calcium—these are minerals that are also regulated by the kidneys, and their concentration in the blood is largely determined by kidney function. And it’s not just the filtering capacity, because the kidney is able to remove these minerals due to other needs, for example, secretion or less reabsorption; so it’s more complicated than just filtering.
Organic and inorganic acids: now that’s going to be very important because depending on your diet, the acids that you have in your blood will change. If you have a high acid-producing diet, that may actually harm your kidneys, but to a large degree and for a while, your kidney is able to remove more acids. There is more acid to be removed, but this is not just filtering capacity; the kidney has a special mechanism through so-called buffers to remove these acids. And if the kidney doesn’t do that, then the kidney is going to get pretty sick, and that will also depend on your diet. And we will talk about diet in terms of acids and other things later on. So we see that the kidney is a miracle; the kidney is able to regulate acid, potassium, phosphorus, calcium by very complex mechanisms, not just a filter.
So, secretion and metabolism of hormones: erythropoietin is a hormone that participates in red blood cell production and it is produced by the kidney. And so, yes, when your kidney is very sick, then there is not enough of this hormone, so we need to give it to you—and we do. Conversion of vitamin D: vitamin D metabolism is very much affected by the kidney, so when your kidney is severely diseased, then your vitamin D metabolism needs to be helped out a little. But again, you may have a decrease in filtering capacity to a large extent before these functions are affected, and sometimes not even then.
So what I’m saying here is that the various functions of the kidneys need to be assessed individually in every single individual patient. And remember there is more, because a lot of kidney patients actually have diabetes, and insulin health is also affected by the kidneys. Antibiotic action is also affected by kidney function. So all of these things need to be looked at in an individual patient.
The kidney being a miracle may not be such a miracle for a long time if you have true kidney disease, because if your kidney has started to fail, depending on your original kidney disease, then you may have other problems arising from kidney disease. For example, your sympathetic nervous system is overactive, and so that may mean that you have heart disease and other blood vessel disease or vascular disease. You might retain salt, and these two things then can cause high blood pressure and high blood pressure disease—or it’s called that is really blood vessel disease, and it’s based on blood vessel inflammation. So kidney disease may contribute to blood vessel disease by promoting inflammation, for instance by increasing salt retention and other means.
So kidney disease may compromise nutritional status; so you don’t have a good appetite, and even if you have appetite, the nutrients are not built into your tissues because of toxins. So your muscle mass may go down, your immune response may be weaker. You might not be able to do enough exercise, and that means more infections, and then that means more inflammation—and inflammation and inflammation being the same, this might also further impact your blood vessels. So in kidney disease, the gut flora (the microbiome) is dysfunctional; it does not work properly. So what that means is that you have less absorption of nutrients but also more poison production. You have a compromised barrier; you may absorb from the gut all kinds of poisons that cause inflammation in blood vessels, and all of a sudden your blood pressure goes up because of this inflammation.
The summary of all this is that the kidney has a lot of functions, and all of these functions need to be assessed individually in an individual patient. If the filtering capacity decreases by some influence other than the kidney disease, most other functions are affected minimally or not at all, or if they are, they restart as soon as the influence stops. For instance, you have diarrhea, you filter less for a day or two, then you eat and drink, your diarrhea stops, and everything goes back to normal; in the meantime, your vitamin D metabolism remains largely the same.
But if you have true kidney disease, then all of these functions will try to decline, one a little bit more rapidly, the other one a little bit more slowly. So reduced filtering capacity estimated by lab work is something different than kidney disease diagnosed by physicians. Sometimes medications and treatments—certain blood pressure medications called ACE inhibitors, diuretics—and if you take too much blood pressure medicines, or even if you take just the right amount but your very high blood pressure goes back to normal, your filtering capacity goes down but then remains stable, protecting your kidney. So again, lab work may look worse early but then it remains stable for a long time, years, decades, or whatnot. —
So then, if it’s not just labs, then what is exactly kidney disease? Well, if you are unfortunate enough to need a kidney biopsy, then this is what the biopsy shows: this blue thing means that there is a lot of scarring in the kidney because you had, for instance, some kind of inflammation in the kidney for a long time, years or decades. And that means that you have a true kidney disease, and your kidney function sooner or later will go down. All of your kidney functions.
In the ultrasound, this is shown as white; you know, this white thing here are scars. So whether or not it’s a hereditary disease, an autoimmune disease, some kind of metabolic disease such as diabetes, or blood vessel inflammation, it usually causes more or less permanent damage affecting all of the functions of the kidneys, and depending, of course, on the underlying kidney disease, because there are a lot of different kinds. And then you end up with scarring and with failing functions. There are common features toward the end: scarring, shrinking, so the kidney is smaller. And no matter how many times you assess kidney function, all of the time you see that it’s less and less and less. So you have a time dynamic; things are getting worse all the time.
But not all kidney diseases are like this. Some kidney diseases, especially when they are caught early, can be watered or even cured so that you do not end up with scarring. And that is why it’s important: if you have labs that are abnormal, you have to repeat them from time to time, you have to do a full workup, and then treat the underlying disease. And treating the underlying disease means complete examination and specific treatments for that underlying disease, not just looking at your kidney function. Common patterns in kidney disease: any damage to the kidney that is longstanding or repetitive may cause permanent kidney damage leading to failure of function. Sometimes the nature of the damage is more apparent—for example, obesity, heart failure, diabetes, or cancer. Sometimes the cause remains unknown and may affect anyone at any time, even children. Children very often have hereditary diseases; they inherit some kind of trait, but they also have diseases that we do not know the cause of. So it’s important to see what kind of disease it is, and if it’s caught early, most of the time it can be treated.
Failure of other organs: if you have lung disease, you may develop kidney disease sooner or later; if you have liver disease, it’s the same thing. If you have prostate problems and the urine is not able to flow properly, it’s blocked or partially blocked, then that can cause kidney disease, and then the underlying process needs to be controlled. And remember: chemotherapy, painkillers for chronic joint pain; so a lot of medications can cause this repetitive damage, but very often even those can be treated if you stop these medications early or maybe use a different form of chemotherapy.
Yes, there are a lot of kidney diseases, a lot of causes for your kidneys to fail, but the most common problem is stress and metabolic disease. So now that we understood that whenever you have kidney disease your doctor needs to look at a lot of things and assess these things individually in every single patient according to the patient’s needs, in our next video we are going to see some common patterns: what causes kidney damage in a lot of people. So until next time, thank you for your attention and goodbye for now.
