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Urinalysis: Introduction

by Carlo Raj, MD
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    00:01 Today our topic brings us into the analysis of urine How important is this? Quite With urine analysis, we'll take a look at general examination we'll take a look at the various types of dipsticks Yes , I said various types of dipsticks that are important for us to then measure whatever metabolite that we're looking for in the urine Is that clear? Now I understand that sometimes when you do a general dipstick, that you may or may not find the chemical that you're looking for based on the suspicion of the diagnosis that you're making for your patient So how do you know which dipstick to use? The history.

    00:42 So all that you're doing in this section as we go through urinalysis and the different types of dipsticks It is important that you understand, well the history comes first then use this information that you're given from urinalysis as either confirmation or to complement and support the diagnosis that you've come up with we'll take a look at the sediments and their various morphology of that that you find within the urine when we analyze Now each one of these terms that we then find in the urine well, you've heard of cast before you've heard of different types of cells such as WBCs and RBCs all these becomes really important for us But as I said, at first it's about the pathophysiology Making sure that you have your foundations strong before we even take a look at urine Let's begin Now, this table.

    01:34 There are a few tables that we'll be looking at in this lecture series And there will be overview to spend a little bit of time to make sure that you understand each one of the statements that I'll be making So let me walk you through this First component of urine on general examination that you will be conducting or you will be given in terms of information either from notes from SOAP notes, or perhaps from your question Well then, have you determined or well, how do this occur in terms of color? If it's a dark yellow, maybe concentrated urine So therefore, tell me about your patient.

    02:12 Maybe perhaps, dehydrated? Maybe there is excess sweating? And remember as to what happens in excess sweating There is hypotonic loss of sodium and so therefore what's your plasma osmolarity? It's increased.

    02:29 If your plasma osmolarity is increased, then now you tell me, Based on lecture series at this point, these should be reflex answers, aren't they? If they're not, then maybe perhaps go back and lay down the foundation When your plasma osmolarity is increased, then you'll have your osmoreceptors up in the hypothalamus releasing ADH, down they come to the collecting duct Now what do they do? They then remove that fluid and water from your collecting duct resulting in what kind of urine? A concentrated urine. What color is this? Dark yellow.

    03:02 Let's move on. What if you found bilirubin? Completely different story, isn't it? completely different story.

    03:09 In hepatobiliary pathology, we will have done well, issues with jaundice So therefore, we'll take a look at prehepatic, hepatic, posthepatic jaundice and what it means for you to actually find bilirubin in your urine Now there are different types in biochemistry you have already discussed What bilirubin metabolism means and what type of bilirubin you should be finding in urine versus that type of bilirubin which then indicates a pathology so for example, when you get the bilirubin down in the intestine at some point, you go through various mechanisms in which you finally form some of that urobilinogen The urobilinogen will then contribute to the pigmentation of our stool Did you see your stool this morning? What color was it? That was brown - that's stercobilin or when you took urination or you went pee, then what color was your urine? Oh it was yellow, or golden. And that's a type of urobilin, isn't it? But ultimately, there are other components of bilirubin such as conjugated bilirubin and if that ends up in your urine, that is a pathology.

    04:15 and that is something that we have discussed in hepatobiliary and so therefore the color of that urine here in fact would be dark yellow Increased UBG would mean urobilinogen and what that basically means is that say for example, you're not able to properly, let me..

    04:29 Let me ask you something, are you ready? Now if you get something into the intestine, is that then going to end up in your urine? Once again, if you get a substance in your intestine, this is just simple physiology but this is where students go wrong.

    04:43 If you get something in your intestine, how in the world is that gonna end up in your urine? if it ends up in your intestine, ends up in your stool, I'll give you that But in order for you to get something in your kidney, and this is important Then you have to reabsorb that substance from the intestine into the plasma and then the plasma goes to the kidney and then it gets filtered only then will it end up in the urine, right? So whenever you find increased urobilinogen, It only means that there's excess amounts of this in your blood or in your plasma It is only then that it gets filtered, so maybe perhaps there is blockage of what? Maybe there's some kind of hepatic obstruction And if there's some type of biliary obstruction then the only method out from your liver would be into the plasma.

    05:28 Keep that in mind.

    05:28 Now, so this is just one statement in which there's all this understanding that took place prior to you actually examining and analyzing urine for urobilinogen.

    05:40 What about vitamins? Well as far as vitamins are concerned, what kind of substance or or what kind of characteristic does a vitamin have to have for it to be in your urine? It has to be conjugated, it has to be water soluble, doesn't it? And so that then becomes important in terms of let's say that you take Vitamin C, or vitamin B vitamins Some of those are water soluble but could they then end up in your urine? Quite a bit actually.

    06:04 So all those vitamins that you end up taking, remember a lot of those if you don't require it, they end up in your urine gets reabsorbed into your plasma and then it gets filtered dark dark yellow color, number one.

    06:16 A second type of color - red or pink what does this mean? The urine actually looks red.

    06:21 For example, you wake up in the morning and that first micturition that first micturition, passing of urine Oh my God, it's red! How did that happen? It's gonna scare you for the patient isn't it? How in the world did you end up getting blood in your urine? well that one that I just gave you where you wake up in the morning Well what happened that night perhaps? Your respiratory rate, increased or decreased? Let me walk you through this Decreased respiratory rate. huh? You're holding on to carbon dioxide.

    06:54 So for that moment at night then, what is your pH? A little bit decreased, It's called a respiratory acidosis.

    07:01 So at night, you go through respiratory acidosis and then all of a sudden, the RBCs are undergoing severe intravascular hemolysis so all of these, comes into simple pathophysiology well not so much simple but you're strong the time that you spent understanding a condition called paroxysmal nocturnal hemoglobinuria.

    07:24 In paroxysmal nocturnal hemoglobinuria, the problem is genetically in which the complement system ends up destroying your RBCs intravascularly in conditions that are acidotic. welcome to "nocturnal" - at night you wake up in the morning, we find your urine to be, well that's the patient himself or herself that ends up seeing the red urine Hematuria, that's what this is.

    07:49 then we have hemoglobinuria. what does that mean to you? well this is something like intravascular hemolysis in which you are literally losing hemoglobin through your glomerulus and this is an example that I gave you such as PNH-Paroxysmal Nocturnal Hemoglobinuria All I'm doing at this point is giving you a little bit of history based on some of the findings that you might have based on the color of urine What if it's myoglobinuria? How'd you think about this, or how should you be thinking about this? myoglobin is the hemoglobin for the muscle hence, myo- right? and so therefore say that you get into a crush injury and if there's a crush injury literally, there's a damage through the skeletal muscle in which you are then releasing myoglobin into the plasma.

    08:33 and that then ends up in the urine, what do we call this? Myoglobinuria what color might these then give your urine? red or pink Drugs such as phenazopyridine or urinary anesthetics possibly and then porphyrias the big one here, you might have heard of acute intermittent porphyria.

    08:53 acute intermittent porphyria, a porphyria in which many of the symptoms and signs that you find with AIP would begin with the letter "P" meaning to say that you will end up having pink urine there'll be "abdominal Pain", there is (P) "psychosis".

    09:11 Let's take at least 3 Ps right now, for acute intermittent porphyria, one of them being "pink urine", Do you see the significance of urine analysis thus far? You thought that you could just go through this and memorize that? you know me well enough, well that's not what we're gonna do It's about you looking at this, seeing this, hearing this and truly coming up with a few differentials in your head as to what's going on with your patient.

    09:35 To continue.

    09:36 what if it's smoky colored urine? acid pH urine converts the hemoglobin into what's called "hematin" and a common finding in "nephritic", and if you're dealing with nephritic you should be thinking something along the lines of perhaps IgA nephropathy why did I say IgA nephropathy? Because that would be the most common type of glomerulonephritis.

    09:59 So nephritic, what does that mean to you? You pay attention to letter H and a lecture series that we have together in which we talk about glomerulonephritides and we talked about nephritic syndrome, I will have you highlight in your head the leter "H" for nephritic why? that "H" means, hypertension, hematuria.

    10:18 It could mean that you have smoky colored urine Hematin is what you're paying attention to What if it was black urine? That's crazy, isn't it? could you imagine urinating and then upon exposure to oxygen and the environment, it turns black? What's your diagnosis? Well this could be something like alkaptonuria, autosomal recessive disorder with a deficiency, and you must memorize, and you have memorized in biochemistry, the enzyme called homogentisate oxidase. Homogentisate oxidase is the enzyme that's deficient in a condition called alkaptonuria now that you find as being black, what happens? take a look it's a homogentisic acid in the urine, and therefore upon exposure to light as soon as it comes out into the world as urine does, it then turns black and some of those black substance may also accumulate with the new cartilage and such called ochronosis Continue.. We talk about clarity.

    11:19 so one major component that we just completed our discussion, is color.

    11:23 what about clarity? What if it's cloudy urine? this is alkaline pH, so what does this mean to you? normal finding, most often due to - phosphates.

    11:33 Cloudy. What if it's cloudy urine with acid pH? normal finding most often due to - uric acid so you wanna be familiar as to what the pH of the urine is in great detail In general, it tends to be on the acidic side, but if it's a little bit more acidic say that it's below 4.0, then you start thinking about uric acid if it's on the higher side, maybe 5.5 and maybe 6.0 then you're thinking along the lines of phosphates depending as to what the physiologic needs of the patient is then you have others, others in terms of clarity, bacteria, WBCs we will be focusing upon these as we progress further through urinalysis do you see now it's to how we create a picture of a table and the more number of times that you're able to give clinical tags and let me give you a tidbit of advise here it is not imperative at this point for you to go through every single detail and don't get frustrated if you're not able to come up with a differential immediately at least pick one or two components of each one of these characteristics if it's dark yellow, at this point if all that you can remember is bilirubin Okay it's fantastic, it's okay at least give yourself one tag of a differential, right? if the only thing that you can, at this point, remember what pink as being a symptom like myoglobinuria, that's okay, you keep coming back, you keep coming back everytime you come back, you give a clinical tag, you give a clinical correlation with each one of these findings and before you know it, you have a whole host of differentials You do that throughout medicine with me, and you will be in fantastic shape when it comes to pathology Another component would be specific gravity What's this mean? literally, the gravity that the urine is exhibiting, evaluates urine concentration and dilution now before we move on, if your urine's concentrated, what color is it? dark yellow.

    13:27 Next, if your urine is concentrated, what do you expect the gravity to be? use common sense here, Obviously, it will be increased Let's take a look.

    13:36 If your specific gravity is above, now this you'd want to memorize, 1.023, the usual limit of specific gravity is usually by 1.010 What I mean by that is 1.010 Use 1.010, How would you say that in layman's terms? say "10.10" make your life easier now here we have something that's graded 1.023 that's high specific gravity.

    14:01 next, well okay that sounds good but what does that actually mean? because you're responsible to do what? you're responsible to actually interpret labs in your hands maybe on a computer screen, what have you? and you should be able to take a look at urine osmolarity, take a look at what's in the parenthesis here urine osmolarity at 900 milliosmoles may I ask you something? what's normal plasma osmolarity? normal, approximately 300 mOsm when you get this plasma into the Bowman's space and the proximal portion of the PCT which of the urine osmolarity approximate? 300 Ah, what's my point? If you start moving down to descending limb, you start raising urine osmolarity doesn't 900 seem a lot more dramatically increased than 300? it is.

    14:54 is 900 concentrated or diluted urine, please? It's concentrated urine.

    15:00 which is specific gravity? higher understand the concept first then you put in the values indicates urine concentration and excludes the intrinsic renal disease excludes it. why? that means that ADH had an opportunity to remove the water and thus increase concentration Let's continue.

    15:22 so we have hypotonic urine - has a specific gravity of 1.015, what does this mean? Don't memorize this either, understand the concept first hypotonic urine, what kind of urine is this? it's diluted urine did ADH work yet? Probably not. Because you created diluted urine the urine osmolarity, take a look at this, what's normal plasma osmolarity? approximately 300 mOsm, and then you get them to the Bowman's space, what is the urine osmolarity there? Approximately 300 mOsm take a look at urine osmolarity in the parenthesis, what does that say? 320 mOsm in the urine What does that mean to you? hypotonic urine.

    16:01 what do you call that in layman's terms? diluting urine what is the specific gravity? decreased.

    16:07 understand the concept, then you memorize less than 1.015 Let's move on..

    16:14 Urine osmolarity is the best indicator of urine concentration or dilution We just went through examples here of showcasing that Next, what if it was a fixed specific gravity, okay so then we have here let's say that it's fixed at approximately normal, and we'll use 1.010 correlation with urine osmolarity, lack of concentration and dilution This indicates chronic renal failure I want you to come back up and take a look at the second row here and while we're talking about specific gravity being greater than 1.023 that is concentrated urine. What does that do? that excludes intrinsic renal disease But if your urine osmolarity is fixed throughout the nephron, Do you understand the concept? Nothing is changing.

    17:03 Why? because the kidney is dying Do you understand how important this is? Example, chronic renal failure. How important is this? ridiculously important How often does this occur? Have you heard of diabetic nephropathy? it occurs more often than when we think, huh? specific gravity. We spent a little bit of time here Understand the concepts in putting the values


    About the Lecture

    The lecture Urinalysis: Introduction by Carlo Raj, MD is from the course Urinalysis.


    Author of lecture Urinalysis: Introduction

     Carlo Raj, MD

    Carlo Raj, MD


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