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Uric Acid

by Carlo Raj, MD
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    00:01 Let’s go into other types of stones, shall we? This is a uric acid, so think about as to where you get uric acid.

    00:06 Be careful not to get this confused with urea, one has nothing to do with the other.

    00:11 Uric acid, a breakdown of your purines which only means it’s a breakdown of DNA, which only means it comes from cells.

    00:18 Are we okay or are you producing too much uric acid? And so you should know about the purine salvage pathway from bio chemistry and the fact that maybe, there’s a deficiency of enzyme.

    00:28 We all have heard of Lesch-Nyhan syndrome and that is a deficiency of HGPRTs, right? Hypoxanthine guanine phosphoribosyltransferase deficiency resulting in increased uric acid, that child, what does that child wanna do? Complete self-mutilation.

    00:44 Crazy, but literally, this child, you’ve seen a child like this, it’s sad, right? The biting on their gums, they’re trying to really hurt themselves, they can’t help it.

    00:53 Maybe if they’re playing on a bike, they literally put their hands in the spokes of the wheel to break their hands.

    01:01 I mean, it’s so crazy, self-mutilation, Lesch-Nyhan, that’s one cause.

    01:06 What else may cause this? Well, cancer, chemotherapy is a big deal and with chemotherapy, you’re breaking down lots and lots, and lots of cancer cells, cancer cells of course contain DNA, and so therefore, you’re releasing all this DNA into circulation, you may then be introducing what? Good, uric acid is of course referred to, take a look at the notes here.

    01:27 We have tumor lysis syndrome.

    01:29 Are we clear? So that’s important.

    01:32 Of course, your patient that may also have gout and that would be perhaps a patient, usually a male, maybe middle aged, and during the holidays, might be consuming quite a bit of meat, and also, consuming quite a bit of beer, and then all of a sudden, what happens? Oh, my goodness, my toe hurts, my big toe hurts, right, podagra.

    01:53 So that’s all part of uric acid issues.

    01:56 Alright, so here, as the name applies, uric acid, decreased pH, here, things get a little different.

    02:02 This crystal that you’re going to find is going to be rhomboid or rosette and the crystal that’s rather on x-ray will be radiolucent, on CT, minimally visible because it’s lucent.

    02:17 The first stone now that we’re seeing in which its characteristics are clear on ultrasound, U/S stands for ultrasound, may also be visible.

    02:26 In other words, factors include, we talked about this dehydration, I told you about during let’s say holidays, not consuming as much proper hydration, maybe drinking too much alcohol perhaps, and then may result in precipitation.

    02:41 What else? Climate, acidic pH, hyperuricemia we talked about tumor lysis syndrome.

    02:47 What do you wanna do here with the urine? You want to alkalinize it or maybe not even produce the uric acid to begin with.

    02:55 Welcome to our drug called allopurinol and of course, allopurinol inhibits that enzyme called xanthine oxidase but it takes a little bit longer, doesn’t it? You’re never gonna use allopurinol for acute gout, it would never work, it takes too long.

    03:09 So this will be more for your chronic gout, good, move on.

    03:14 Now, we come into cystine.

    03:16 With the cystine stone, it’s rather interesting.

    03:18 We talked about this back in nephrology a little bit where we referred to different reabsorption issues and I gave you the pneumonic COLA.

    03:28 If that worked for you, cystine, ornithine, lysine, arginine, and I want you to focus upon cystine.

    03:33 And during our conversation with cystine, we talked about how we have a clear - and there was a little cartoon there and it shows you six sides of a hexagonal crystal.

    03:42 A hexagonal crystal, clear.

    03:44 So with that said, we have now a cystine decreased pH in your urine.

    03:50 X-ray will be radiolucent and sometimes visible on CT.

    03:53 The big thing here is the fact that it’s clear and hexagonal.

    03:57 You’re not able to properly take in your cystine.

    03:59 It’s autosome recessive disease, genetic, in the PCT, you’re not able to properly take up there your amino acids, cystine, ornithine, lysine, arginine, and these may then form staghorn, so be careful with that term staghorn.

    04:14 All staghorn means is a huge stone actually but take a look at the picture here.

    04:18 That looks rather large.

    04:20 It could actually be confused by a layman or if you’re not paying attention on gross examination as being a staghorn, meaning, what? Oh, maybe magnesium ammonia phosphate, but it’s impossible if the urine was pH and it was decreased as for uric acid.

    04:37 And if you’re thinking about cystine, a decreased pH, here you go.

    04:43 And then if it’s staghorn in dealing with magnesium ammonia phosphate, its pH will be increased.

    04:48 Management, sodium, nitroprusside test is positive is what you’re looking for here.

    04:55 Alright, so we actually do a nitroprusside test and that’s positive up here.

    04:58 A couple of things that are quite important for cystine stones.


    About the Lecture

    The lecture Uric Acid by Carlo Raj, MD is from the course Nephrolithiasis.


    Included Quiz Questions

    1. Coffin lid
    2. Dumbbell
    3. Hexagonal
    4. Rosette
    5. Rhomboid
    1. Escherichia coli
    2. Proteus mirabilis
    3. All are likely organisms.
    4. Klebsiella.
    5. Staphylococcus saprophyticus
    1. Percutaneous nephrolithotomy
    2. Diuretic therapy
    3. Prophylactic antibiotic therapy
    4. Citrate therapy
    5. Low sodium diet
    1. Uric acid
    2. Calcium oxalate
    3. All are visible.
    4. Magnesium-ammonia-phosphate
    5. Calcium phosphate
    1. Rhomboid
    2. Hexagonal
    3. Envelope
    4. Dumbbell
    5. Coffin lid
    1. Alkaline urine
    2. Decreased urine volume
    3. Tumor lysis syndrome
    4. Hyperuricemia
    5. Arid climate

    Author of lecture Uric Acid

     Carlo Raj, MD

    Carlo Raj, MD


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