Chemical Dipsticks: Blood & Nitrates

by Carlo Raj, MD

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    00:01 Continue our discussion of chemical dipsticks in urinalysis Let us now take a look at blood Now up into this point in part one of our lecture series we went ahead and talked about in great detail urobilinogen and bilirubin and the difference between those types biochemically it's important that you get those down now we'll go into blood as being part of our analysis in the urine detects RBCs, hemoglobin, myoglobin. What are the differences? Well say that you end up having RBC that has to squeeze through the glomerulus Yes, I'm being dramatic.

    00:41 As an RBC squeezes through the glomerulus, is it possible that it might then become disfigured? You know what kind of RBC that's called? I just kind of gave it away It's called dysmorphic.

    00:53 Amazing, huh? What's morphology mean? shape.

    00:55 What's dys mean? Messing it up.

    00:58 So a dysmorphic RBC would be an RBC that would be more of a glomerular origin.

    01:04 Are we clear? So type of RBC that you see becomes important and relevant for us.

    01:09 What if you find just RBCs in general in the urine? That could be anything.

    01:14 What does that mean? That means that RBC could be from damage of your tubule, not from the glomerulus.

    01:21 or it could be damage done in the urinary bladder maybe due to cystitis Do you see the difference now? So what you wanna do is anatomically separate your urinary bladder from your kidney, and even within the kidney separate your tubules from your glomerulus Hemoglobin and myoglobin; Remember myoglobin, if you find this in your urine will then give you your pinkish red myoglobinuria and the way that this occured was due to crush injury and then I gave you hemoglobinuria as well, and that would be red remember, thaat patient woke up in the morning and, "Aah, it's a red urine" panicked a little bit. What happened? Wake up in the morning, or maybe after exercise.

    02:04 those are acidotic environments that the patient was in prior either during sleep or during exercise Acidotic- respiratory or metabolic, respectively.

    02:15 And in doing this process, in a patient in paroxysmal nocturnal hemoglobinuria end up having red urine.

    02:24 hematuria; renal stones being an example.

    02:27 Hemoglobinuria; intravascular hemolytic anemia.

    02:30 So, Dr. Raj you just told me about PNH.

    02:34 Yeah, I did. What do you think PNH is? Paroxysmal Nocturnal Hemoglobinuria.

    02:40 Not that I'm asking what the abbreviation mean I'm asking you what category of hemolysis is it? Is it intra- or extravascular? If it's hemoglobinuria, it has to be intravascular, is that clear? Dr. Raj, what about extravascular? Remember that sickle cell patient? I met a sickle cell patient.

    02:59 Sickle cell disease, homozygous- acute chest pain There was issues with hands, dactylitis - that's extravascular hemolysis.

    03:09 What was significant in that patient? It was jaundice, it's significant.

    03:15 Hematology's interesting, isn't it? Myoglubinuria, crush injury.

    03:19 What else might you find with myoglubinuria? use common sense.

    03:23 If your muscle's actually being broken down.

    03:26 Skeletal muscle, shall we say got into an accident, a crush injury.

    03:31 What else would you expect to find apart from myoglobinuria? Isn't creatine kinase a component of your skeletal muscle? Of course. So you have increased serum creatine kinase.

    03:45 Hope that's clear, let's move on.

    03:48 Nitrites you'll find this to be interesting Many times in microbiology, they end up talking about this but to differentiate pathologically what kind of urinary tract infection your patient is suffering from, you'll find this to be neat.

    04:02 Nitrites is my topic.

    04:04 It detects nitrites produced by nitrate-reducing uropathogens This include your E.coli How important is that? Very.

    04:15 One of the most common causes of urinary tract infection Something like E. coli, gram negative organism And what might you be looking for here? It's nitrites.

    04:27 Okay, now the test is sensitive and specific respectively, 30 and 90 percent, specific at 90 percent and requires, this is where its gets really interesting, requires approximately 4 hours for nitrate-reducing your pathogens to convert the nitrate into nitrite.

    04:44 Now, the reason that I'm being so dramatic here about the names, is because, don't confuse this with "esterase", right? Even though E.coli has an "E", do not equate it to esterase.

    04:58 This is nitrite.

    04:59 In patients who had urinary tract infections frequently have what? increased frequency of urination, which explains the test has poor sensitivity.

    05:09 You see it has to how wonderful this is explained in terms of why sensiitivity is a measly 30 percent but specificity is a high 90 percent.

    05:19 Think about your patient, urinary tract infection, what are they doing? "Hey doc, I have a burning sensation" most likely a female And what is she doing? She's going to the bathroom so she can urinate Do you think that perhaps that she's actually evacuating the organism during this time and not allowing for sufficient amount of time for the conversion to take place? Of course.

    05:39 So sensitivity could be quite low But if your patient is presenting as such and you know this about the pathogenesis then you have properly managed your patient.

    05:54 Now this versus esterase.

    05:57 leukocyte, what's that mean to you? pyuria.

    06:01 What's leukocyte mean? WBCs.

    06:05 What type of WBC might you find most notably with bacteria? Neutrophils.

    06:11 If it's esterase, then it detects the esterase in your neutrophil Well, you kinda know about neutrophil in pulmonology, or respiratory pathology and the reason I say that is because neutrophil up in your lungs, when it comes to, let's say take care of antigens in great abundance, Something like maybe smoking, What's that enzyme that neutrophil releases there in the lung? Good, elastase.

    06:41 At some point, if you release too much elastase in the lung, What's your diagnosis? Very good. Emphysema.

    06:50 This is neutrophil dying where? In the urinary tract.

    06:54 What enzyme is it releasing? Esterase.

    06:59 80 percent sensitivity in infections.

    07:01 Examples, now be careful. Why? Listen Urethritis, I want you to go anatomically from distal to proximal, Urethra is infected. Urethritis, are you going to find neutrophils? Of course. Okay Cystitis, infection where? Urinary bladder.

    07:22 Are you gonna find neutrophils and esterase? Yes.

    07:27 Pyelonephritis, go more proximal. Kidney infection now abscess formation, flank pain, back here in the flank and with pyelonpehritis, neutrophils? Dr. Raj what the heck was your point? My point is this, WBC cast WBC cast are different from neutrophils, is that clear? What do you mean? Casts are only coming from the kidney, Cast will never be found in the urethritis.

    07:57 Cast will never be found with cystitis.

    08:01 Cast are almost always found with pyelonephritis.

    08:05 In all three, would you find cells? Yes.

    08:09 If with bacteria, what kind of cells? Obviously, neutrophils.

    08:13 What is this test? esterase.

    08:16 Move on.

    08:16 Sterile pyuria, neutrophils present but negative standard urine culture Now one big organism, such as Chlamydia trachomatis urethritis, TB and drug induced interstitial nephritis.

    08:30 Now all of these in which you would find neutrophil but you come back to be negative for culture.

    08:36 Two big ones here, chlamydia and the other one would be interstitial nephritis Further discussion we'll have with interstitial neohritis in other lectures.

    About the Lecture

    The lecture Chemical Dipsticks: Blood & Nitrates by Carlo Raj, MD is from the course Urinalysis.

    Included Quiz Questions

    1. Muscle breakdown
    2. Dehydration
    3. Nephritic syndrome
    4. Nephrotic syndrome
    5. Urinary tract infection
    1. Neutrophils are found in urethritis, cystitis, and pyelonephritis.
    2. Neutrophils are not found in urethritis, cystitis, and pyelonephritis.
    3. WBC casts are found in urethritis, cystitis, and pyelonephritis.
    4. Hyaline casts are found in urethritis and cystitis.
    5. WBC casts are not found in pyelonephritis.
    1. Escherichia coli
    2. Enterococcus bovis
    3. Mycoplasma pneumoniae
    4. Streptococcus pyogenes
    5. Staphylococcus aureus
    1. Chlamydia trachomatis
    2. Escherichia coli
    3. Staphylococcus aureus
    4. Streptococcus pyogenes
    5. Proteus mirabilis
    1. Presence of neutrophils
    2. Presence of monocytes
    3. Presence of macrophages
    4. Presence of lymphocytes
    5. Presence of platelets

    Author of lecture Chemical Dipsticks: Blood & Nitrates

     Carlo Raj, MD

    Carlo Raj, MD

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