Liver Explained! Function, Pathology, Diseases, & Cirrhosis
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Liver Explained! Function, Pathology, Diseases, & Cirrhosis

August 30, 2019


welcome to another MedCram lecture
we’re going to talk about the liver there’s been some requests to go over
the liver and we’re going to look over this and in terms of an overview and I
first like to start with the anatomy so if you can imagine the liver it’s a
pretty large organ sits in the abdomen and it has a number of functions which
we’re going to go over the first thing you’ve got to look at as with anything
is see what goes into it and sees what comes out of it the first thing that
you’ll notice what the liver is that there is two inputs to the liver there
is what’s called a portal vein and hepatic artery so this is the hepatic
artery and there’s two of them they split and this is not drawn to
anatomical scale it’s kind of schematic and this is coming from the heart so
this is oxygenated blood the other input is the portal vein and this is coming
from the intestines and this is important because a lot of medications
that you ingest and like pills the first place that they go is to the liver and
so the metabolism of these medications first occur in the liver this is called
first pass metabolism and then they go on to the heart and that’s the next part
of the drawing here you get the hepatic vein and so you’ve got two inputs and
one output and so it’s got to go through the liver if it’s coming from the portal
vein from the intestines now in terms of output or exocrine we know where happens
to endocrine it goes into the blood but in terms of exocrine there’s two major
outputs you’ve got a hepatic duct a right hepatic duct and a left to paddock
duct and they combine into the common hepatic duct and then they meet up with
the cystic duct which is from the gallbladder which stores bile and that
forms the common bile duct which then dumps into the intestines and that’s how
the body gets rid of it so the liver really has two functions it has it
endocrine functions and it has exocrine functions the endocrine functions are
hormones that are produced in the cells they regulate glucose they produce
albumin there’s a whole bunch of things that
they do and their output gets dumped into thee to the hepatic vein and that
goes on to the heart or it gets pumped for the whole body the heart also pumps
oxygen blood to the liver because the liver just like any other organ needs
oxygenated blood to survive and that’s where it gets its supply but the major
source of blood supply to the liver is actually from the portal vein and this
includes the stomach the duodenum the jejunum the ileum the colon all the way
down to the rectum basically is blood all of the fatty acids all the nutrients
that you get absorbed to take a first pass and they go to the liver and that’s
kind of the circulatory and the the endocrine and the exocrine functions of
the liver of course the exocrine functions are it
produces bile bile Issa’s are these things that break down fats it what’s
makes your poo look brown and 50% of it approximately is stored in the
gallbladder at each meal so can be ejected into the cystic duct into the
common bile duct and then into the duodenum so it can help in aiding in
digestion the next I want to talk about are the blood tests that are associated
with the liver and and these are sometimes confusing let’s go over those
the first one or the first type of blood test that I want to go over or what I
call the cytotoxic blood tests so what are the cytotoxic blood tests well the
first one is the AST this is also known as the SG ot this enzyme is actually
made in the liver in fact it’s not specific to the liver it’s in a number
of cells but you can see it in a number of cells but also in the liver the other
one is the alt albumin and the PT by the way the alt is also known as the s GPT
okay so ast and alt are simply enzymes that are in the hepatocyte
and when the hepatocyte dies these enzymes get released
so in this essence these are like cardiac enzymes like when you have a
heart attack you release ck ck-mb and troponin when you have an injury of
liver cells that’s when the ast and the alt go up now just like you can have
congestive heart failure and a low ejection fraction and your heart is not
contracting very well and you have heart failure you might not have elevated CK
CK and B intra ponens the same way that if you can be in liver failure in other
words your hepatocytes are not producing the things that the liver should do you
could also have low ast and alt so what do we use ast and alt for these are
basically markers for hepatic inflammation so hepatic inflammation is
tracked by and seen as elevations in the alt and the ast and we’ll get into a
little bit about that in just a second so the ast specifically has low
specificity for the liver okay it’s seen in the peri portal key pata sites okay
whereas the alt has a high specificity for the liver okay so think of the L
here and the alt as being standing for liver where as s is more for muscle but
they’re both seen in the liver now in terms of both of these the ast and the
alt they both go up in all forms of liver injury it’s only good for recent
injury so if there’s old injury you won’t see these elevated okay these tell
you nothing about residual function okay so if these are low it doesn’t mean that
your liver function is low it just means there’s no current inflammation going on
in the liver it doesn’t tell me if my liver is good and they’re productive or
if my liver is damaged and not functioning well and the damage is not
dose-dependent so if the ast and the alt are coming
down this doesn’t necessarily mean as a good
thing or it’s a bad thing in other words a decrease could mean better or worse so
in other words if the ast and alt are coming down it could be that the liver
is so damaged that there’s no more cells to damage or it could be that the ast
and alt are coming down therefore the damaged has ceased okay it’s kind of
like fire and smoke this is kind of like your smoke now you could see smoke go
away for two reasons either because there’s no more stuff to be burned or
because the fire has been put out okay I hope that makes sense okay so I cleared
the page so we can talk about albumen and Pt let’s talk about albumin we’ve
talked about album before specifically when we’re talking about anion gap
albumin is a very complicated protein it’s made in the liver and it’s pretty
reliable for looking at chronic hepatocellular injury so if the albumin
is low that usually equals chronic liver injury so someone has an acute problem
with the liver there albumins usually stay up and the reason why that is the
case is because it’s got about a 20-day half-lives which means it takes a long
time for the albumin levels to start to go so I would say this is a good marker
for chronic liver disease finally in the cytotoxic category let’s talk about the
PT so what is the PT PT is the prothrombin time and it’s pretty
reliable for both acute and chronic about a cellular disease so it’s acute
and chronic the other way of looking at the PT is also the eye and R so for
instance the PT might be 10 the INR is 1.0 usually the PT is about 10 times
that of the INR but not always and this is pretty important and I’ll tell you
why because the PT or the INR simply measures the time of prothrombin to do
its work in other words to have clotting it’s a clotting time and clotting times
require many different enzymes that are made in the liver this is important so
that because any enzyme that is not successfully made in the liver is going
to interfere with the pt/inr so it’s very sensitive in fact the
pt/inr is the most sensitive liver function tests that can be done in other
words this is the first thing that starts to get bad as the liver starts to
fail because it requires so many proteins that are synthesized in the
liver and so what are the things that are associated with the PT well its
factors you may remember this from the clotting cascade but factors related to
vitamin K which are 2 7 9 10 also 1 and 5 are related to the PT so what are some
causes that could do this well if the liver is not synthesizing these factors
it’s going to take longer for coagulation to occur and therefore your
PT and your INR will go up so in liver disease instead of it being a nice 1.0
you start to see it to go to 1.5 2.0 etc this is usually a good sign of chronic
liver disease or acute liver disease and it tells you just how bad their livers
are now what are some other things other than liver disease that could cause it
obviously if the patient has low vitamin K that’s going to be confounder if the
patient obviously is on coumadin which is a blood thinner that’s gonna confound
it or if the patient has hemophilia that’s obviously gonna confound it so if
they have low vitamin K just give them vitamin K if they have cumin and
obviously you’re not going to use this test to see if they have liver disease
because you’re trying to get their INR up anyway because that’s why they’re on
a blood thinner in the first place okay so let’s review the ast is a blood test
that will tell you if there’s a cute damage it has a lower specificity for
the liver than does alt it’s increased in all types of liver injury it’s only
good for recent injury there’s no indication of residual liver functional
capacity the damage is not dose dependent all of those go for the alt
except the alt is a little bit more specific so I would expect the alt to be
higher if it’s specific to liver disease the one exception to this is if you have
alcoholic liver disease in which case the ast and the alt may be very similar
sometimes that you even hear two to one or three to one ratio of ast
to alt in alcoholic liver disease okay the albumin is reliable for chronic
hepatocellular injury it’s synthesized in the liver it’s a marker for chronic
liver disease and it’s half-life remember is about 20 days the PT is
probably the most sensitive blood tests for liver disease and as a result you’ll
see these elevations and chronic liver disease remember it’s obviously going to
be elevated if you’re given the patient warfarin or coumadin or things of that
nature great so that concludes this join us for our next lecture which is going
to talk about cholestatic liver function tests thanks very much

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  1. Thank you for watching our video. We'd really appreciate if you checked out the rest of our videos on the liver (LFTs, hepatitis, cholestatic diseases) on our website for free: https://www.medcram.com/courses/the-liver-explained-clearly

  2. I'm a med student and I'm rotating in internal medicine so this really helpful for those test we do on our patients and simplifying it for me to understand.

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