Assessing Kidney Function: Proteinuria

00:01 Okay, so we talked about assessing GFR and measuring kidney function that way but there's another way that we can also measure kidney function or assess how kidney function is doing and that is really by looking at proteinuria that's protein in the urine.

00:15 So it's really defined by abnormal quantities of protein in the urine and we talked about remember before at the beginning of the lecture that this is really a clinical marker of kidney damage.

00:25 Just to remind ourselves, normal quantity of protein in the urine is typically less than than a 150 milligrams over a 24-hour period of time.

00:35 And we also talked about how albumin is the principal component of protein in the urine.

00:40 And typical amounts of albumin are about less than 30 milligrams over a 24-hour period of time.

00:49 So when people exceed that then they have an abnormal amount of protein in their urine.

00:54 So there are a couple of different methods that we can use in order to measure protein in the urine.

01:00 Number 1 and probably what's most simple for people is to just do a urine dipstick.

01:04 This is essentially in a colorimetric test that doesn't really quantify the exact amount of protein but it tell it, does tell you whether protein is present depending on how dark that urinary dipstick colors.

01:17 Now another more accurate way to look at things as actually getting a 24 hour urine measurement for protein collection.

01:23 So this is going to provide us a total protein the total amount of protein that's excreted in the urine over a 24-hour period of time.

01:30 If we do this we do need to measure urinary creatinine as well to ensure that that our patients have obtained inaccurate collection.

01:38 But we just talked about before we were at talking about creatinine clearance how difficult it really is to do a 24-hour urine collection and you really don't want to have your patients do that over time in order to follow their proteinuria.

01:52 Now we can use something else called the protein to creatinine ratio, or the albumin to creatinnine ratio.

01:58 This is actually a spot urinary measurement of protein or for albumin and we measure that to creatinine.

02:07 It's going to estimate a 24 hour urine protein or albumin values.

02:10 So what somebody excretes within a 24-hour period of time So most people will generate between about one to two grams of urinary creatinine.

02:20 And this is how we can use this.

02:22 So I'm going to illustrate a couple of points here.

02:24 In men, They usually generate somewhere between 20 to 25 milligrams per kilogram of urinary cretinine daily again, assuming that they have more muscle mass.

02:33 So if I have an 80 kilogram gentleman, then he's going to make about 1600 milligrams of urinary creatinine.

02:41 That's the amount of protein that he's going to excrete in his or that's the amount Of creatinine that's he's going to excrete in his urine.

02:48 If I have a woman again presuming that she has less muscle mass than a man.

02:53 Usually women will generate somewhere about 15 to 20 milligrams per kilogram of urinary creatinine daily.

02:58 So if I have a 60 kilogram woman, then she's going to generate somewhere around 900 milligrams of urinary creatinine.

03:05 So you can see that between 900 and 1600 most people again are close to that spectrum of one gram of creatinine daily.

03:14 So the way I can estimate how much protein somebody has in their urine As I basically take an aliquot of urine at a random time and that is going to give me that urinary protein or urinary albumin measurement.

03:26 I take an aliquot in that same aliquot of urine.

03:30 I'm going to get that spot assessment of urinary creatinine.

03:33 If I take that ratio, then that gives me the amount of protein estimated that they make within a 24-hour period of time.

03:41 Now you can see because men generate a little bit more creatinine than women, then it's probably going to underestimate with their true proteinuria is, and in women, it might slightly overestimate the amount of protein that they make in a 24-hour period of time, but what's really helpful about the using these spot ratios.

04:01 Is it something that we can follow over time? And it's something that we can use to assess therapeutic targets and make sure that the medications and other things that we're doing to treat our patients are actually working in decreasing proteinuria.