Chemical Dipsticks: Bilirubin & Urobilirubin

by Carlo Raj, MD

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    00:01 Bilirubin Okay, so bilirubin we've talked about earlier when we were looking at the color What color is that going to give you, your urine? Well that, for the most part will be your yellow Now, the discussion here for dipstick - bilirubin detects conjugated bilirubin So Dr. Raj, I thought you just told me that you'd find bilirubin in your urine and in your stool? You even told me to take a look at my stool from this morning which you said was brown.

    00:27 Yeah, that's exactly what I told you. But why did I tell you to do that? Because that type of bilirubin is your urobilin or your stercobilin.

    00:36 Is that the conjugated bilirubin? Now at this point if you feel completely lost about bilirubin metabolism Guess what, this would be a good time for you to review your bilirubin biochemistry We don't have time right now So, I'm telling you this If you find conjugated bilirubin in your urine, this is a problem This is a pathology, so now let me give you a differential.

    00:58 What if you had liver damage? What if you had some type of obstruction known as choledocholithias? Say that three times fast, it's actually kinda fun.

    01:10 Do it: choledocholithiasis.

    01:12 or you have liver damage.

    01:13 Isn't that fun? Come on now, let's have fun with that information.

    01:17 So now, you cannot, now listen, now we'll get serious That bilirubin now has been conjugated You know that conjugating enzymes are in the liver You know about UGT, or UDPGT, it's all the same thing But it undergone the process of glucoronosyltransferase Okay so if you're conjugating in the liver and you don't have an enzyme supply problem in the liver Then you are conjugating your bilirubin, are you not? Yes, you are.

    01:43 That conjugated bilirubin should end up in the bile and then eventually in the intestine and then through the process of bacteria and such will then form your different types of bilirubin: either urobilin or stercobilin And that should end up in your stool and your urine, respectively But what if you couldn't get that conjugated bilirubin out into the bile What are you forced to do? What did I tell you earlier How do you get something in your urine? It has to be filtered from the plasma, are you picturing that? It has to be filtered from the plasma If you just have something in the intestine, I'd give you the stool, but it won't be in the urine.

    02:20 Your kidney doesn't filter the intestine, it filters plasma.

    02:25 It's a conjugated bilirubin if it's forced to go onto the blood either due to through obstruction or maybe liver damage Then what are you gonna find in urine, pathologically? Are we clear now? It has to be conjugated bilirubin But Dr. Raj, why not unconjugated bilirubin or indirect bilirubin? Because that'll give you your discoloration, yellow skin- that's jaundice because that's lipid soluble So in order for you to understand the significance of conjugated bilirubin here, You must understand the biochemistry and physiology for all this to come together Let's continue.

    02:58 Bilirubinuria: viral hepatitis, obstructive jaundice.

    03:01 Voila! there's your differentials But guess what, you already predicted that because that's exactly what we discussed.

    03:08 You can't memorize this, how many times have I said this.

    03:12 But it takes time to understand, but don't get frustrated.

    03:16 Keep coming back, a tidbit, just a little bit every single day Consistency, digest it. Trust me, it will become a party.

    03:24 Urobilinogen. Normal to have trace amounts.

    03:27 Normal urine color is due to, there it is, urobilin.

    03:31 Are we seeing this? Now more importantly, urobilin is different from our previous discussion just now, of conjugated bilirubin They're different.

    03:41 Conjugated bilirubin to you, pathology, differentials, Oh, maybe there's liver damage. Oh, maybe there's obstruction.

    03:49 Urobilinogen, yeah the urobilin should be normally present in your urine.

    03:53 Stercobilin in your stool.

    03:54 Now, absent urine urobilinogen increases or if you have absent urine urobilinogen, you're thinking about obstructive jaundice and if you find increased urine bilirubin, Okay see how these terms sound very much alike? Urobilinogen, it's trace amount should be normal. Bilirubin should not.

    04:17 If you're obstructed, give yourself an example.

    04:20 such as a stone. If you have a stone in your biliary tree, can I get my bilirubin into my bile? No, you cannot.

    04:31 Where are you forced to go into? Tell me, I need this from you.

    04:36 You're forced to go into your blood, you're forced to go into your plasma.

    04:39 Who is? the bilirubins.

    04:41 See if you find increased urobilin or bilirubin, that is not good.

    04:45 obstructive jaundice Example? something like choledocholithiasis Next, increased urine urobilinogen, absent urine bilirubin. What's this mean? extravascular hemolytic anemia.

    04:57 Wow, what are we doing here? We're putting out this is an examples of complete integration of various systems as we're seeing Give an example of extravascular hemolysis.

    05:10 Who's this patient? Young guy, african american boy, running, likes to play, is on the track team while running, all of a sudden stops and feel pain in the chest and in the fingers You take a look at your patient.

    05:24 Well, the patient, kinda difficult to find the jaundice But right around the eyes, there's icterus in the mucosa, icterus.

    05:31 Who's your patient? sickle cell disease.

    05:34 I gave you an African boy who's running, feeling pain in the chest, pain in the fingers What is this called? It's called cclusive crisis.

    05:47 Microvascular occlusive crisis, acute chest syndrome.

    05:52 What's this called in the hand, the pain? Dactylitis.

    05:57 Is this intra or extravascular hemolysis? Take your time.

    06:02 The spleen is destroying the RBCs in great abundance This is extravascular hemolysis.

    06:08 Another one, they're also falling to the category of extravascular, Take a look at your example, Hereditary spherocytosis.

    06:15 Two differentials for extravascular.

    06:18 What's happening here? You are releasing your RBC and bilirubin at great abundance This bilirubin, unconjugated ends up in the skin, gives you jaundice no doubt This vast amounts of bilirubin also will arrive at the liver You are going to conjugate this Look at this, any problems with the liver and extravascular hemolysis? No, no, no. Maybe have issues in spleen later on That's a different discussion.

    06:48 But the liver is conjugating, conjugating, conjugating, conjugating, everything that it's getting, it's trying to conjugate.

    06:54 So therefore, how much urobilinogen do you have in your urine? increased.

    07:00 Do you have obstruction with extravascular hemolysis? Yes or no? No.

    07:06 So therefore, you have absent urine bilirubin.

    07:10 Your objective at this point? Stop here for a second.

    07:13 And I need you to take a look at this discussion, with the discussion right above where we talked about absent urine urobilinogen and increased urine bilirubin Do you see as to how after 6 hours, 7 hours, 8 hours of taking exam you're on your rotation, you are tired.

    07:32 You might be tired now and I only spent what, 15 minutes with you.

    07:36 and then on the 6th hour, you're supposed to think like this? where all your terms should be absolutely perfect? Yeah, that's how alert you need to be.

    07:45 Is it stressful? It is. But you need to spend time is what I'm saying.

    07:49 and understand this. let's continue..

    07:50 Increased urine urobilinogen, increased urine bilirubin.

    07:54 this should be a mixed picture and this would be something like hepatitis.

    07:58 so this would be another section of urobilinogen and walking through the different components that becomes really important discussion take a look at the second column, what's this category? Discussion.

    08:09 You notice it doesn't say "memorization". is that clear? That's what these are! These are discussions.

    08:15 And once you get this done, you can have a conversation with any doctor, at any point in time, and you will not feel foolish

    About the Lecture

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

    Included Quiz Questions

    1. Absent urine urobilinogen and increased urine bilirubin
    2. Increased urine urobilinogen and urine bilirubin
    3. Absent urine urobilinogen and decreased urine bilirubin
    4. Decreased urine urobilinogen and increased urine bilirubin
    5. Decreased urine urobilinogen and urine bilirubin
    1. Decreased urine urobilinogen
    2. Increased urine urobilinogen
    3. Absent urine bilirubin
    4. Extravascular hemolysis
    5. Vaso-occlusive crisis
    1. Conjugated bilirubin is not physiologically seen in the urine.
    2. Conjugated bilirubin is physiologically seen in the urine.
    3. Bilirubin dipstick detects unconjugated bilirubin.
    4. Bilirubin dipstick detects lipid soluble bilirubin.
    5. Bilirubin dipstick cannot detect conjugated bilirubin.
    1. Elevated urine urobilinogen and bilirubin
    2. Decreased urine urobilinogen and bilirubin
    3. Elevated urine urobilinogen and decreased bilirubin
    4. Bilirubin dipstick is a diagnostic tool.
    5. Urobilinogen dipstick is a diagnostic tool.

    Author of lecture Chemical Dipsticks: Bilirubin & Urobilirubin

     Carlo Raj, MD

    Carlo Raj, MD

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