Clinical Application of Creatinine: Overview

by Carlo Raj, MD

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    00:01 Now the clinical application of creatinine is pretty much what this entire lecture series is about. Do we use creatinine clearance? Yeah, but rarely. So what does that mean? You really are thinking about your patient suffering from renal disease. In the process of renal failure. What is the number one cause of renal failure? Diabetic nephropathy. So if your patient over a long period of time has diabetic nephropathy, then you can pretty much predict that your patient is going to go into renal failure and you want to truly assess as to what the functionality of the kidney is and that can be the threshold, the critical point at which the patient is then necessitated or is required to go on dialysis and vary from patient to patients so we are not going to get into actual kidney function or percentage that then takes you into dialysis, but it is important for you to understand how to correlate the creatinine that you will get in which say you go from one and will keep it simple. Remember from the blood, if you get 0.6 to 1.2 for learning purposes, we are going to say 1.0 we are going to repeat all this upcoming. All I am doing here is introduction and then when we actually see it, then it will be a positive reinforcement. So if we say that blood creatinine is 1.0 and we keep our GFR simple as well with the rate of 100, we are going to use those values so that we can use creatinine in a clinical application.

    01:43 So we are clear about what is happening. If your creatinine moves up from 1.0 to 2, is that good or bad, that is your first question? Keep it simple. Bad. How bad? If your creatinine that you are measuring in blood moved up from 1.0 to 2, guess what happened? You weren't filtering, why? It is kidney disease. That is no joke. What do you mean no joke? How dramatically would you lose kidney function when you move from 1.0 to 2.0? Fifty percent. That means 50 percent of the kidney function has been lost because the creatinine is stuck in the blood. Now we will reinforce that very fact as we move on, but I want to make sure that I make an impact now. So because it requires timed urine collection, generally considered a nuisance.

    02:41 What is the creatinine clearance? Instead, what we do. Understand this point versus the points that I just made, which is here you as a clinician are quickly going to assess the functionality of the kidney by checking the creatinine in the plasma. It is a surrogate marker. It is the perfect marker. Of course not, why? Because it is slightly secreting.

    03:05 Keep that in mind. So if there is a huge change taking place in the kidney that creatinine that you are going to measure in your plasma is not going to be the best indicator. I hope that is clear. So at what point would you perhaps recommend creatinine clearance. If you know for a fact that let us say that your patient came in and the creatinine levels in plasma were 2.0 and an approximate assessment of GFR sure, but then how do you get a better assessment? Why not recommend a creatinine clearance? That is all about next step of management. This whole thing that I have been talking to you about with creatinine and its assessment of your kidney. Let us go into little bit more detail.

    03:50 Lets say that this is plasma creatinine and it is inversely proportional to GFR. What does that even mean Dr. Raj? How do you use this with the patient? That's a lot of math granted. Let us do an example. Let us say we give creatinine. May I ask you one more time normal levels of creatinine approximately 0.6 to 1.2. If you use that you will be in good shape. Trust me. So now you got a creatinine level 1.0. What does that mean? That means you are within normal range of GFR and we will use GFR here for learning purposes as 100 and I want to harp on the units here. Milliliters per minutes,allow my voice and what I am telling you to haunt on you forever more. The units of GFR milliliters per minute.

    04:38 Are you hearing me in your dreams? Now, what if your creatinine moved up to 2? If it moved up to 2, what is this? what kind of creatinine is this? Plasma. So what happened? Oh no! GFR has dropped.

    04:52 How much? By fifty percent. So if normal GFR was 100, the GFR now dropped down to approximately 50 milliliters per minute. That is the biggest drop in percentage as you go from 1 to 2.

    05:06 Now let us say your creatinine moved up to 3, where is my creatinine? This means plasma.

    05:11 What is normal? 0.6 to 1.2. I'm going to keep repeating this. If you moved up to 3, then you lost, well, now you have moved down to 33. And as you go from 3 to 4, it is 25. Now you tell me where is the biggest drop? As you went from 3 to 4 or 1 to 2. What am I referring to? The creatinine.

    05:32 Where? In your plasma. If your creatinine goes from 1 to 2 in the plasma, you have dropped by 50 percent. As the creatinine goes from 3 to 4, you have dropped down by 8 percent.

    05:44 But the point is this. Once you get past 2 and it keeps rising just because the drop is not as dramatic as you go from 3 to 4, it doesn't mean that the kidney is not in bad shape. Thirty-three percent is horrible kidney function, approximately 25 percent is even worse now. As I said for learning purposes, this is not a nephrology course. This is an introduction nephrology in just enough detail so that when you walk on the ward and you take your boards, you will be successful as what objective is. So 25 percent is quite low. Now in terms of is that patient required to go on dialysis well that depends on the overall well-being of your patient and that can differ from patient to patient here.

    06:33 I hope that is clear and only if it is are you permitted to move on. Next.

    06:40 Clinical application further. That's everything we just talked about. So let us go and read here a little bit. We have a GFR and as we go from 1 to 2 that is much more of a significant drop as opposed to your creatinine go from 4 to 5. Is that clear? What does that mean to you again? Close your eyes. Where is this creatinine? In the plasma compared to creatinine clearance. This is plasma. What is normal? 0.6 to 1.2. We are going to use 1. As we go from 1 to 2, how much did your kidney function drop? By 50 percent, much more significant.

    07:11 Now, if it goes from 4 to 5, my goodness the drop is not going to be as dramatic, but both are really bad and how do you assess this further? Well. We will walk into that right now. I truly want to make sure that we lay down the foundation for creatinine. Now as we get older, understand that maybe perhaps our GFR drops naturally. But before move on also keep in mind with the creatinine, it is slightly secreted. What does that mean to you? One more time. Tell me the relationship between the clearance and GFR. GFR is filtration.

    07:49 Clearance is what is actually being evacuated and the creatinine it is slightly secreted thus your clearance is greater than GFR. Understood?

    About the Lecture

    The lecture Clinical Application of Creatinine: Overview by Carlo Raj, MD is from the course Renal Diagnostics.

    Included Quiz Questions

    1. Creatinine clearance is greater than GFR, because of the secretion of creatinine.
    2. Creatinine clearance is greater than GFR, because of the reabsorption of creatinine.
    3. Creatinine clearance is less than GFR, because of the secretion of creatinine.
    4. Creatinine clearance is greater than GFR, because of the filtration of creatinine.
    5. Creatinine secretion is greater than GFR, because of the reabsorption of creatinine.
    1. 25 ml/min
    2. 50 ml/min
    3. 125 ml/min
    4. 25 ml/hour
    5. 25 ml/sec
    1. Younger age
    2. Diabetic nephropathy
    3. Muscle breakdown
    4. Decrease in glomerular filtration.
    5. Decrease in creatinine secretion.
    1. Diabetic nephropathy
    2. Glomerulonephritis
    3. Polycystic kidney disease
    4. Renal artery stenosis

    Author of lecture Clinical Application of Creatinine: Overview

     Carlo Raj, MD

    Carlo Raj, MD

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