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Liver Disease: Introduction and Commonly Used Liver Test

by Carlo Raj, MD
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    00:01 Hello. Welcome to hepatobiliary diseases.

    00:05 Here, our topic at first will be viral hepatitis.

    00:09 Remember that when you discuss hepatitis, there could many, many causes as we go through our topic of hepatites.

    00:17 At first, it will be viral, but it could be auto-immune, it could be alcohol, it could be many causes.

    00:22 Do not always assume that it’s viral.

    00:25 Let’s begin.

    00:28 The liver tests that you should be familiar with, known as a liver function test, include the following.

    00:35 In hematology, we talked about bilirubin quite a bit.

    00:39 And here, we talk about bilirubin as being part of pre-jaundice or pre-hepatic jaundice, hepatic jaundice and post-hepatic jaundice.

    00:48 Here, with bilirubin accumulating, not exactly sure as to what part of bilirubin metabolism could be affected.

    00:55 What do you mean, Dr. Raj? Watch.

    00:58 Say that you brought bilirubin, unconjugated type, indirect is what – is what we use clinically.

    01:06 And you bring this lipid-soluble substance to the liver, but the chaperone, the albumin then drops it off.

    01:13 Obviously, the first step here by the liver is to make sure that it conjugates it, correct? What does conjugate mean to you? It means turning something that’s lipid-soluble into water-soluble.

    01:25 And why is our objective – why is this objective so important? Because we’re trying to, at some point, get this bilirubin out into excretion.

    01:34 And in order for you to get bilirubin to the urine, you must conjugate it at some point in time.

    01:39 My point is this.

    01:41 When you have liver disease, maybe perhaps the enzymes have been affected.

    01:46 What enzyme is responsible for conjugation? The operative word always is going to be called glycosylation.

    01:53 And let that be UDPGT or UGT (uridine glucuronosyltransferase).

    02:00 Without going into that type of detail, if the liver is damaged sufficiently and the enzymes are not working properly, then what component or what faction of your bilirubin are you then noticing? Good. The unconjugated bilirubin.

    02:16 Or let's say that there is enough damage to the liver that now, at this point, the entry point into bile has been blocked.

    02:27 But, remember, bilirubin is part of your bile as well.

    02:30 So, therefore, now, you could get conjugated.

    02:33 However, the type of bilirubin that you are looking for laboratory-wise could be conjugated.

    02:39 So, what's the point? And what are you paying attention to on your boards and on your wards? You can have a mixed picture of bilirubin, or call mixed jaundice, when you have a liver disease.

    02:53 Keep that in mind.

    02:54 If that is not clear, make sure that you go back and take a look at proper and full bilirubin metabolism.

    03:00 So, what I have just discussed with you medically, clinically makes a lot more sense.

    03:06 Next. My topic is liver function tests.

    03:10 What if the liver is damaged sufficiently enough where the liver inadequately doesn't put out albumin? Welcome to something like cirrhosis.

    03:24 Anything that causes end-stage liver disease or if there's sufficient liver damage, there is every possibility that albumin could be diminished.

    03:33 What does albumin contribute physiologically in your circulation? What part of your Starling’s forces? Good. Oncotic pressure.

    03:43 Thus, if albumin is not present, oncotic pressure drops.

    03:47 Where is now – fluid now escaping into? Into tissue.

    03:53 There are two coag tests or coagulation tests.

    03:57 You notice I didn’t say platelet test, right? What's the platelet test that you're extremely familiar with or should be? That’s bleeding time.

    04:06 In hemodynamics, we talked about platelets.

    04:09 I’m not going to bring that up here, but either platelet dysfunction or quantitatively you have thrombocytopenia, then the bleeding time will be affected.

    04:16 Here, however, the coagulation factors that you should be familiar with include – well, from the liver, what are you synthesizing? II, VII, IX and X, the vitamin K dependent factors, on one end, pro-coagulation.

    04:34 And what are the two anti-coagulation factors that the liver produces? Protein C and protein S.

    04:42 From henceforth, whenever you think about the liver, remember there are pro and anticoagulant factors that are, in fact, being secreted from it.

    04:51 Correct? Next, clinically speaking, which are the two tests are you going to measure of your coagulation to tell you that the liver may or may not be functioning properly? It's PT, prothrombin time; INR, international normalizing ratio.

    05:11 What is the PT that you want to know in terms of the actual time? 11 to 15 seconds.

    05:18 You know that for your boards, you'll be in good shape.

    05:21 Thus, if the liver is not functioning properly, the synthesis of your coagulation factor drops, what then happens to your PT? Increases.

    05:33 You have ALT.

    05:35 This is your alanine or alkaline alanine type of aminotransferase, so you have the two transaminases, ALT and AST.

    05:43 And the ratio here do become very important.

    05:46 Since our topic in this section is going to move into viral hepatitis, would you please be able to tell me which one of these transaminases would be elevated more so? Would it be ALT or AST in viral hepatitis? Good. ALT.

    06:02 Just to make sure that we’re clear and to have a little bit of fun with this, I want you to toast to AST.

    06:10 Toasting what? Alcohol.

    06:13 So, whenever you have alcohol-induced hepatitis, there the AST will be increased versus ALT, a 2 to 1 ratio.

    06:23 Continue.

    06:26 When does alkaline phosphatase come into play? And do not confuse ALP with ALT.

    06:33 ALP, alkaline phosphatase, would come into consideration if the biliary tree has been affected.

    06:41 Obviously, the liver and the biliary tree are one unit.

    06:47 You cannot separate one from the other.

    06:49 If there is enough damage that’s taken place to the liver, understand that you are then going to affect your bile or biliary canaliculi, and so therefore may cause damage or injury to the biliary system, therefore, increasing ALP.

    07:05 Just to make sure we’re clear, would you tell me as to what other set of diseases and they’re different type, but still ALP, would be used for? Obviously, bone disease.

    07:17 Now, the true tests of liver function are PT and albumin.

    07:20 So, those are the two that you definitely want to focus upon, but absolutely understand that each one of the components that we're dealing with here will play an important role, so that you can diagnose your patient properly.

    07:32 The others only signify altered function and do not correlate with overall synthetic activity of the liver.

    07:39 So, of all of these, the two that actually give you proper functioning of liver include PT and albumin.


    About the Lecture

    The lecture Liver Disease: Introduction and Commonly Used Liver Test by Carlo Raj, MD is from the course Cirrhosis – Liver Diseases.


    Included Quiz Questions

    1. Increase in the unconjugated bilirubin
    2. Increase in the conjugated bilirubin
    3. Increase in PT
    4. Increase in APTT
    5. Increase in gamma glutamyl transferase
    1. Bound T3
    2. Free T3
    3. AST
    4. ALT
    5. Conjugated Bilirubin
    1. Albumin and PT
    2. AST and ALT
    3. Conjugated bilirubin and unconjugated bilirubin
    4. Gamma Glutamyl transferase and ALT
    5. Alpha feto protein and AST
    1. ALT
    2. AST
    3. Gamma Glytamyl transferase
    4. Alpha feto protein
    5. 5 Deoxy nucleotidase
    1. 2:1
    2. 1:2
    3. 3:1
    4. 3:2
    5. 4:1
    1. Alkaline phosphatase
    2. AST
    3. ALT
    4. Alpha feto protein
    5. Prothrombin time

    Author of lecture Liver Disease: Introduction and Commonly Used Liver Test

     Carlo Raj, MD

    Carlo Raj, MD


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