Liver Function Tests - an overview

Summary

This educational video by Dr. Matt delves into liver function tests, explaining what they are and their purpose. It covers key enzymes like AST, ALT, ALP, and GGT, and liver-produced substances like albumin, prothrombin time, and bilirubin. The video discusses why these tests might be ordered, such as for patients with liver disease, medication-induced liver injury, or high-risk groups. It also provides a schematic approach to interpreting test results, distinguishing between jaundice causes, cholestasis, and hepatocellular injury, offering valuable insights for medical professionals.

Takeaways

• 🧬 Liver function tests (LFTs) are blood biomarkers that indicate liver health, including enzymes and liver-produced products like albumin and bilirubin.
• 🔬 Enzymes such as AST (Aspartate Transaminase), ALT (Alanine Transaminase), ALP (Alkaline Phosphatase), and GGT (Gamma Glutamyl Transferase) are released by the liver and can signal liver injury if elevated.
• 📈 Albumin, prothrombin time, and bilirubin levels are liver-produced substances that, when abnormal, suggest liver dysfunction in protein synthesis, clotting factor production, and bilirubin processing, respectively.
• 🏥 LFTs may be ordered to investigate liver disease, medication or poison-induced liver injury, alcohol use, family history of liver issues, or high-risk groups such as those exposed to viral hepatitis or illicit drugs.
• 🔎 Jaundice, a yellow discoloration of skin and eyes due to bilirubin buildup, can be assessed through LFTs to determine its cause, such as pre-hepatic, intra-hepatic, or post-hepatic conditions.
• 📊 Bilirubin levels above 1.2 mg/dL may indicate jaundice and require further investigation into the cause, which could be related to red blood cell breakdown or liver processing issues.
• 🚫 High levels of ALP and GGT in conjunction suggest cholestasis, a blockage in bile flow, but must be differentiated from non-liver sources like bone tissue.
• ⚕️ AST and ALT are key indicators of hepatocellular injury; their levels and ratio can help differentiate between acute and chronic liver conditions, with AST being more sensitive to alcohol.
• 📉 Decreased albumin and clotting factors, along with increased clotting time, indicate liver's compromised ability to produce necessary proteins and regulate blood clotting.
• 🛑 Hepatocellular injury affects bilirubin processing, leading to issues in secretion and excretion, and can result in both pre-hepatic and post-hepatic jaundice.
• 🧐 Understanding the nuances of LFTs, such as the role of individual enzymes and liver-produced substances, is crucial for diagnosing and managing liver conditions.

Q & A

What are liver function tests, and what do they measure?

Liver function tests, also known as liver chemistries, are blood biomarkers that indicate how well the liver is functioning. They measure the levels of certain enzymes and proteins that are either produced by the liver or are indicative of liver function, such as AST, ALT, ALP, GGT, albumin, prothrombin time, and bilirubin.

What is the significance of enzymes like AST and ALT in liver function tests?

AST (Aspartate Transaminase) and ALT (Alanine Transaminase) are enzymes that are released from the liver. Elevated levels of these enzymes can indicate liver injury or disease, as they are markers of hepatocellular damage.

What are the liver-produced products that liver function tests measure?

The liver-produced products measured by liver function tests include albumin, a protein that helps maintain blood volume and pressure; prothrombin time, which reflects the liver's ability to produce clotting factors; and bilirubin, which is processed and conjugated by the liver for excretion.

Why might a healthcare provider order liver function tests?

Liver function tests may be ordered to investigate potential liver issues, such as a history of liver disease, exposure to hepatotoxic medications, alcohol use, or a family history of liver disorders. They can also be used as a screening tool for high-risk patients or to monitor liver function in patients with conditions that may affect the liver.

What is jaundice, and how can liver function tests help diagnose its cause?

Jaundice is a yellow discoloration of the skin and eyes due to a buildup of bilirubin. Liver function tests can help determine the cause of jaundice by measuring the levels of bilirubin and other liver enzymes, which can indicate whether the issue is pre-hepatic, hepatic, or post-hepatic.

How does the liver process bilirubin, and why is it important?

The liver processes bilirubin by conjugating it, making it water-soluble and allowing it to be excreted via bile. This process is crucial for the elimination of bilirubin from the body and helps maintain normal bilirubin levels, which is important for overall health.

What is the difference between pre-hepatic, intra-hepatic, and post-hepatic causes of jaundice?

Pre-hepatic causes of jaundice are related to increased red blood cell destruction or issues with the enzyme that conjugates bilirubin. Intra-hepatic causes involve problems within the liver cells, such as diseases affecting liver function. Post-hepatic causes are related to obstructions in bile flow, such as blockages in the bile ducts.

How can the ratio of direct to total bilirubin help determine the cause of jaundice?

A higher proportion of direct bilirubin compared to total bilirubin can suggest a post-hepatic cause of jaundice, such as cholestasis, where there is a problem with bile excretion. Conversely, a higher total bilirubin compared to direct bilirubin may indicate a pre-hepatic cause, such as increased red blood cell destruction or issues with bilirubin conjugation.

What role do bile acids play in the diagnosis of cholestasis through liver function tests?

In cholestasis, bile acids can accumulate and cause an increase in the activity of enzymes such as alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT), which are found on the bile canalicular membrane of hepatocytes. Elevated levels of these enzymes can indicate a problem with bile excretion.

How can the levels of AST and ALT help differentiate between acute and chronic liver injury?

Significantly elevated levels of AST and ALT, such as 10 times the normal value, can indicate acute liver injury, which could be due to factors like viral hepatitis, drug toxicity, or hypoxic injury. Moderate increases in these enzymes, around five times the normal value, may suggest chronic liver injury, possibly due to conditions like fatty liver disease or chronic viral hepatitis.

Why might the ratio of AST to ALT be higher in cases of alcohol-induced liver injury?

The higher ratio of AST to ALT in cases of alcohol-induced liver injury is due to the fact that AST is more sensitive to alcohol's effects on the mitochondria, which can cause it to leak into the bloodstream at a higher rate than ALT. Additionally, chronic liver conditions like cirrhosis can also lead to a higher AST to ALT ratio.

Outlines

00:00

🧪 Introduction to Liver Function Tests

Dr. Matt introduces the video on liver function tests, explaining that these blood biomarkers indicate liver health. He outlines the video's agenda: defining liver function tests, discussing reasons for their use, and analyzing a schematic to understand abnormalities. Key liver enzymes like AST, ALT, ALP, and GGT are mentioned, as well as liver-produced substances such as albumin, prothrombin time, and bilirubin. The importance of these indicators in assessing liver function and disease is emphasized.

05:01

🌡 Causes and Diagnosis of Jaundice

This paragraph delves into jaundice, a condition characterized by yellowing of the skin due to bilirubin buildup. It explains the origin of bilirubin from red blood cell breakdown and its journey through the liver for processing. The liver's histological unit, the lobule, its blood supply, and bile excretion process are described. The role of hepatocytes in bilirubin conjugation and the significance of direct bilirubin (DB) in diagnosing jaundice are highlighted, along with the distinction between pre-hepatic and post-hepatic causes.

10:02

📈 Understanding Jaundice Causes Through LFTs

The paragraph discusses using liver function tests (LFTs) to determine the cause of jaundice. It differentiates between pre-hepatic causes, such as increased red blood cell destruction or enzyme sluggishness, and post-hepatic causes, like blockages leading to cholestasis. The importance of bilirubin ratios in diagnosis is stressed, with high total to direct bilirubin ratios suggesting pre-hepatic issues and vice versa for post-hepatic causes.

15:05

🔍 Investigating Cholestasis and Hepatocellular Injury

This section examines cholestasis, a post-hepatic condition where bile excretion is obstructed, leading to bile acid accumulation and increased ALP and GGT levels. The non-specific nature of ALP is noted, requiring GGT confirmation for liver origin. The paragraph also explores hepatocellular injury, focusing on AST and ALT enzymes, their release from liver cells, and the implications of their levels and ratios in diagnosing acute and chronic liver conditions.

20:05

🛠 Conclusion on Liver Function Test Analysis

The final paragraph wraps up the discussion on liver function tests, summarizing the implications of abnormal levels of liver enzymes and substances. It touches on the effects of hepatocellular injury on albumin production, clotting factors, and bilirubin processing, leading to clinical manifestations like increased clotting time and jaundice. The video aims to provide a clear understanding of why LFTs are ordered and how to interpret their results to assess liver health.

Keywords

💡Liver Function Tests (LFTs)

Liver Function Tests, also known as LFTs, are blood biomarkers that indicate how well the liver is functioning. They are crucial in diagnosing liver diseases or damage. In the video, Dr. Matt explains that these tests can reveal if the liver is releasing certain enzymes due to injury, or if there are issues with the liver's production of proteins like albumin or its processing of bilirubin.

💡Aspartate Transaminase (AST)

AST, or Aspartate Transaminase, is an enzyme found primarily in the liver and heart. Elevated levels in blood can indicate liver damage. The video script mentions AST as one of the enzymes that, when markedly increased, could suggest liver injury, highlighting its importance in LFTs.

💡Alkaline Phosphatase (ALP)

Alkaline Phosphatase, or ALP, is an enzyme that can indicate liver health, particularly in relation to bile flow. The video discusses how an increase in ALP levels could suggest cholestasis, a condition where bile flow is obstructed, which is a key concept in understanding liver function and disease.

💡Gamma Glutamyl Transferase (GGT)

Gamma Glutamyl Transferase, or GGT, is another enzyme that, when elevated, can signal liver disease or biliary obstruction. In the video, GGT is mentioned alongside ALP as an indicator of cholestasis, emphasizing its role in diagnosing liver issues related to bile excretion.

💡Albumin

Albumin is a protein produced by the liver and is one of the liver function tests. Low levels can indicate liver disease or malnutrition. The video script discusses albumin as a product of liver function, and its levels are checked to assess the liver's synthetic ability.

💡Prothrombin Time

Prothrombin Time is a measure of the liver's ability to produce clotting factors, which is essential for blood coagulation. The video explains that the liver's production of these factors is checked through LFTs to evaluate liver health.

💡Bilirubin

Bilirubin is a waste product processed by the liver and its levels in the blood are monitored through LFTs. The video script delves into bilirubin's role in jaundice, explaining how its buildup can lead to the yellowing of skin and eyes, and how LFTs can help diagnose the cause.

💡Jaundice

Jaundice refers to the yellowing of the skin and eyes due to high bilirubin levels. The video script uses jaundice as a clinical sign that prompts LFTs to be ordered, helping to diagnose the underlying cause, such as liver disease or hemolytic anemia.

💡Cholestasis

Cholestasis is a condition where bile flow from the liver is impaired, leading to a backup of bile components in the blood. The video explains cholestasis as a potential cause for abnormal LFTs, particularly affecting ALP and GGT levels.

💡Hepatocellular Injury

Hepatocellular Injury refers to damage to the liver cells themselves, which can be acute or chronic. The video script discusses how LFTs, especially AST and ALT levels, can indicate such injury, with different patterns of elevation suggesting different causes and severities.

💡Hemochromatosis

Hemochromatosis is a genetic disorder causing excessive iron storage in the body, particularly the liver, leading to organ damage. The video mentions it as a potential cause for liver disease that can be identified through LFTs, highlighting the importance of family history in liver health assessment.

Highlights

Definition of liver function tests as blood biomarkers indicating liver function issues.

Introduction of enzymes AST, ALT, ALP, and GGT as indicators of liver injury.

Explanation of liver-produced products like albumin, prothrombin time, and bilirubin.

Reasons for ordering liver function tests, including liver disease history or concerns.

The role of liver function tests in investigating jaundice and its causes.

Importance of bilirubin levels in diagnosing jaundice and its potential causes.

Description of the liver lobules and their function in blood filtration and bile secretion.

Process of bilirubin metabolism and its conversion to direct bilirubin by the liver.

Differentiation between pre-hepatic, intra-hepatic, and post-hepatic causes of jaundice.

Use of bilirubin ratio to identify pre-hepatic causes of jaundice.

Identification of cholestasis through increased ALP and GGT levels.

Differentiation of hepatocellular injury using AST and ALT levels.

Impact of alcohol on AST levels and its distinction from ALT in cases of liver injury.

Explanation of how chronic liver conditions affect albumin, clotting factors, and bilirubin processing.

Distinguishing between acute and chronic liver injury based on AST and ALT levels.

Clinical significance of liver function tests in diagnosing and monitoring liver health.

Practical application of liver function tests in identifying liver disorders and guiding treatment.

Transcripts

hi i'm dr matt and welcome to this video

on liver function tests also known as

your liver chemistries in this video

we'll firstly define what these tests

are

secondly we'll look at some examples of

why they may be ordered and then thirdly

we'll go through a schematic drawing to

try to categorize and make sense why

these may be deranged

so starting with the definition so the

liver function tests are basically blood

parameters blood biomarkers that give an

indication that liver may not be

functioning as well as it should be so

some examples that we'll go through

firstly these are enzymes that are

released from the liver

number one in no order we have one

that's called ast

so that's aspartate transaminase

alanine transaminase

a lp

alkaline phosphatase

ggt

gamma gluta transferase now these are

all enzymes so that will give an

indication if these are markedly

increased there could be a possibility

that liver is injured and releasing

these as a result the next three are

actually products that are produced by

the liver so we have albumin

which is a protein

we have prothrombin thyme which is an

indication of the clotting factors that

are released from the liver

and then lastly we have bilirubin

which is

something that's made outside the liver

but the liver conjugates it to allow it

to be excreted so these four first four

are enzymes these are more to do with

how the liver is functioning or working

because albumin is made there the

clotting proteins are made in the liver

and the bilirubin is processed and

conjugated in the liver so if these are

outside their range it indicates that

the liver isn't functioning whereas

these enzymes indicate it might be

diseased or injured

so moving on to why

may they be ordered firstly

to look at maybe the patient has a

history of liver disease or you are

concerned that there might be a problem

so for instance if the patient comes

with jaundice this is a yellow

discoloration you may want to have an

exploration to figure out why it's

caused so you might have a look at this

panel

you may be concerned that they've taken

a medication so they've taken a poison

or something that could cause liver

injury hepatotoxic medications such as

paracetamol

in america this is acetaminophen or

tylenol but in australia we call it

paracetamol

the patient may have a history of

alcohol use

or they may have a positive family

history of so a known family history of

something that may cause damage to the

liver an example is

hematochromatosis which is basically the

way that iron is stored in the liver or

elsewhere in the body and that can cause

damage and disease to the liver

next we might look at groups that are

high risk so it's a screening tool for

patients that may be in a high risk

category this could be if they've had a

transfusion

a blood transfusion

they've been exposed to

viral hepatitis let's say

or maybe they

have used illicit drugs

now moving to another cause this could

be extra hepatic so this big certain

things that are outside the liver that

could impact the liver so examples here

would be malignancy

so this is cancer so cancer a common a

place where the cancer can spread as

secondary so this is metastasizing it

can go to the liver which then would

suggest that the liver will start to

become dysfunctional and these may start

to increase another example if the liver

has been

hypoxic so a low level of oxygen low

level of blood flow so

let's say shock a patient has a history

of shock

and therefore you're concerned that

liver might be damaged through ischemia

or hypoxic

finally medication there might be

certain medications that might cause

injury so you want to get a baseline

before you prescribe this medication

examples could be methotrexate as i said

paracetamol or vaporate so these are

some examples so there you have it there

are there are some reasons why a

clinician might order lft is to get an

idea of what is happening at the liver

now we're going to have a look at that

schematic

diagram to again to break this down and

make sense of them

now we move to the third part of this

video which is trying to make sense of

why these numbers why the liver function

tests may be out of range what i want to

look at is if your patient has jaundice

how can we figure out what is the cause

of the jaundice by looking at the lfts

and then finally the two biggest causes

of the derangement of lfts cholestasis

which means a problem with the way the

bile is leaving the liver and being

excreted or hepatic cellular injury

which means there's a problem intrinsic

to the liver itself

so let's start with jaundice jaundice is

a yellow discoloration of the skin the

sclera the mucous membranes which is due

to a buildup of bilirubin so the lft

we're going to look for here is

bilirubin

okay and basically anything above 1.2

milligrams per deciliter or per 100 ml

now before we go on we just got to

quickly make sense of where does

bilirubin come from

so bilirubin is the breakdown product of

red blood cells red blood cells will

last approximately 120 days once they

get to that age they get destructed and

killed within certain organs like the

spleen the bone marrow or the liver

themselves now when the red blood cell

is broken down

a lot of the parts will be recycled the

iron gets taken back to the liver to be

reformed into other constituents

the protein the globulins will get made

into amino acid pools but the heme

component will get broken down

phagocytosed by macrophages and

essentially be made into bilirubin

now i'm not going to go through all the

steps

mike has done a video on this so i

encourage you to have a quick look at

that if you haven't covered this before

but the bilirubin in this case will what

we call b

unconjugated bilirubin which means it

has to be carried

with a protein called albumin so that's

a complex that will get transported in

the blood and taken to the liver

before i get to the more detail what i

want to draw your attention to is this

histological unit of the liver there's

about a million of these and these are

called the liver lobules the liver

lobules are these kind of hexagonal

shaped

sections of the liver that has in the

center what we call a central vein which

is the accumulation of blood that has

diffused or percolated through all the

hepatocytes and then all of this central

vein blood will eventually accumulate

and then leave the liver via the

inferior vena cava

but what blood does it receive well it

gets arterial blood so about 20 percent

of arterial blood

is what goes through this lobule and the

70 to 80 of blood is through the portal

vein so those two bloods merge together

as the sinusoid kind of go through these

plates of cells called the parasite and

what goes the opposite direction is the

bile cannuculi which is like a river of

bile that goes out towards the outer

part of the lobule and all of these bile

ducts will start to come together

form the hepatic ducts which then become

the common hepatic duct meets the cystic

duct of the gallbladder and then we have

the common bile duct that goes down to

the duodenum

so it's this unit that i want to refer

you to specifically just one hepatocyte

so just one of those black dots will

focus in here now so this is one

hepatocyte

on the outside so this is the sinusoid

so this is the combination of portal

blood and

arterial blood fuse in through

the hepatocyte will grab things

and metabolize and filter and

do all the different functions that the

liver cells does and everything it

doesn't want it gets put into the bile

conuculide to be excreted out of the

liver but we're focusing on bilirubin

here so bilirubin will be coming along

in the systemic blood remember it's

unconjugated so it's got albumin

attached to it it gets transported

across into the hepatocyte where the

abdomen detaches and then this

unconjugated bilirubin gets taken to an

enzyme called uridine diphosphate

glucosyl transferase or ugt what this

enzyme essentially does it will add a

group to it to make it lipid sorry to

make it water-soluble this now makes it

a conjugated bilirubin

also known as

direct bilirubin so we'll focus on db

direct bilirubin from here this

conjugated bilirubin can get

excreted via a protein called mrp2 and

be put into the bile where it gets

excreted

eventually leaving the liver

as the bile duct goes down into the

intestines where a lot of it will be

metabolized by bacteria

some of it metabolized in a way that it

can be reabsorbed in the bowel with some

of it coming back

absorbed it back across and it does this

big long loop

the rest of it will get taken and put

out into the faeces that's what gives

the brown coloring some of it will

continue on as conjugated bilirubin

which can then get

urinated out and then that can be

cleared as well and the rest will just

go in this cycle

so now with that basis we need to figure

out well what could cause the bilirubin

to be increased

so this first part if your patient comes

to you with that yellowness you don't

really know what the cause and if you

were to do

some of the lfts and just find that

their bilirubin is high you still don't

know what's causing it so let's try to

figure some of this out

the first category of causes is

something that's causing an increasing

amount of red blood cell destruction and

this is what we call pre-hepatic

so if you were to have a patient that

has high amounts of red blood cell

destruction so they've got some kind of

anemia hemolytic anemia or some kind of

problem with their um hemoglobin that

could cause an increase in destruction

that would increase the amount of

hemoglobin coming for bilirubin coming

to the liver or they may have a lot of

hemorrhage hematoma that would also

increase it but another thing that could

increase it is this enzyme could be

slightly

sluggish it's not working as quickly as

it could

the common condition that that could

lead to or could lead to that decrease

in activity is gilbert syndrome so if

you have that syndrome the patient has

that syndrome this is not working so

well so therefore the conjugation speed

is going to be decreased and then you'll

have a up in the uncon unconjugated so

if you want to figure out whether

they've got a pre-hepatic cause

of their jaundice what you will do is

you do a blood test and if you see that

their total bilirubin is proportionally

higher

than their direct

so these two should be in a ratio but if

this one goes much higher to this one it

would suggest that

there's a problem pre-hepatically so it

could be increased destruction or a

problem with this enzyme

now

the other option

now there is intra-hepatic causes but

i'm going to leave it to kind of this

part so

if there's a problem with his excretion

okay that would mean that

the same the right amount of bilirubins

come to the liver the liver is doing

everything it's supposed to do it

conjugates it spits it out into the into

the bio caniculide but there's a problem

downstream there's a blockage for some

reason which means we go backwards so

the bile builds back up that means the

conjugated bilirubin comes back across

and spills across into the blood and

then we see it in the blood okay but

with this post-hepatic cause

in comparison to the pre-hepatic cause

what we actually see is an increase in

the direct

proportionally to the total

so it switches

with the pre so the post hepatic so if

it's a post hepatic cause

you'll actually see a much higher amount

or percentage of the direct

in the total because you've conjugated

it you've gotten rid of it but it's come

back and then it's gone across into the

blood okay so this is one way you can

figure out

what is leading to the jaundice

and so as we said this is a post-hepatic

cause which is essentially going to be

the collostasis which we're going to go

through now so the the remaining part of

your lfts

is to try to figure out is the cause due

to a cholestasis so a problem with the

excretion or a problem with the cell

itself

so let's have a look at this one to

start with

so let's assume that there is a blockage

so there could be a stone

in the bar duct or there could be a

structure so it's narrowed or there

could be a tumor down in the head of the

pancreas

causing the flow to be disrupted in any

case the bi will come backwards so it

will come back up and what you'll see is

the bile acid will come across

back into the hepatocyte

now

on the membrane the bile the biconicular

side of the hepatocyte so this side of

the membrane there is an enzyme here

that can produce

a number of other

and

what this is going to be

is

alp so that's the alkaline phosphatase

and this is generated by that enzyme on

that membrane so when it's exposed to

increased amount of bile acid this

enzyme will become more active which

increases the alp which then is pushed

across into the sinusoid which then goes

into the central vein and the ivc and

then in your blood so if you start to

see an increase in alp

so let's say you do your alp levels and

you've got a big increase or two two

arrows up of alp

you have a suspicion that it's due to a

cholestasis cause

but an important point here is alp

is not specific to the liver it's also

found in the placenta it's also found in

bone tissue so you need to be sure that

it is actually from the liver so there's

another enzyme that kind of works on

that membrane as well and that's the g

g t that's the gamma gluta transferase

so you want to also look for that one

and if that is also up which is kind of

the same mechanism you'll see that one

up as well and if you see ggt up with

alp you are confident that it's

a cholestasis cause particularly if your

direct bilirubin is up as well okay now

for whatever reason let's just say your

alp was up but this was normal and there

was nothing here

you need to suspect that it's coming

from somewhere else outside the liver

for instance

bone is a big one so osteoblasts when

they're highly active they're releasing

this enzyme so this could be recent

fractures or certain conditions where

there's maybe tumors in the bone or

pages disease causing an increase in ap

levels

finally we're going to have a look at

hepatocellular injury so i'll just clear

this off quickly

and the two big enzymes that you need to

be aware of with a paracellular injury

is ast

and a l t

an important thing just to remember

the s here

even though these are found in the liver

the s

the way i remember is also striated

muscle so this can be found in cardiac

muscle and skeletal muscles so it's not

specific to the liver so sometimes

problems with heart or or spleeder

muscles could also increase ast so just

be aware of that but the alt-l is

specific l to liver so this is much more

specific to liver

in terms of asp

asd the majority that 80 is found in the

mitochondria

whereas the majority of alt is found out

in the cytoplasm just to reiterate that

ast 80 is found in the mitochondria 20

in the cytoplasm whereas the majority of

the alts in the actual hepatocyte

cytoplasm itself in terms of the ratio

there's more ast in the cell than alt

but this is

diffused out quicker which means in the

blood these two are about a one to one

ratio so if you would a

normal person and normal

levels of these two they're about a one

to one ratio

okay so we've understood that ast and

alt is more specific to the hepatocyte

injury okay but how do we distinguish

with what kind of injury well if the

numbers are kind of above

10 times what they normally are that's

an indication that there is an acute

injury

and it's

severe

so this is inflammatory based so

anything that's kind of causing

hepatocell inflammation acutely and

quite severely is going to raise the

amount of these two

significantly this could be due to

paracetamol so the toxic effects a viral

acute viral infection like hepatitis or

hypoxic injury like there's not enough

blood coming to the liver which is going

to cause extreme inflammation causing

these levels to go up a significant

amount so this is more acute

causes of liver injury if the number is

only let's say five

times increased it's more suggestive

that it's a chronic effect

okay so chronic effects this could be

things like

fatty liver which could be

alcohol-based or non-alcohol based fatty

liver a chronic viral hepatitis

or certain medications over time

it's important to distinguish though

that ast

seems to be more sensitive to alcohol

the reason well the theory for why that

could be

is a combination of ethanol

causes irritation to the mitochondria

which causes it to spill out and go into

the blood at a higher amount so the

ast like we said it should be one to one

it's a higher ratio with alcohol-induced

injury so the ast could be higher or the

other cause of ast being increased

relative to alt is through more chronic

fibrosis or cirrhosis that causes the

flow the blood flow through the liver to

be sluggish which then reduces the

amount of ast that normally leaves which

then increases its buildup so

ast

increased relative to alt in ratio is

usually due to cirrhosis

and alcohol

finally

because the hepatocyte in the

hepatocellular injury they're not it's

not functioning as well you're going to

see those certain parameters like

albumin album has been isn't being

produced to its normal level same with

the clotting proteins and also the way

that the

bi the way that the bilirubin is

processed through the hepatocyte it's

going to be diminished and they're going

to see the changes a reduction in

abdomen problems with clotting time so

the clotting time increases and we see

problems with the bilirubin processing

that's outside pre-hepatic and

post-hepatic if there's a problem

intrinsic to the cell with the enzymes

and the transport proteins that's going

to play around with bilirubin secretion

excretion as well

so hopefully today you've seen

what liver enzymes are what are the

indications of why they will be ordered

and then we've schematically moved

through to try to make sense why each

one of them may be increased or deranged

outside their normal values