Liver Function Testing

Question 1

Liver anatomy

Answer 1

The liver is located on the right side of the abdomen

It is connected to the biliary system which drains into the duodenum

The liver is made up of hexagonal units called lobules

Question 2

Lobule structure

Answer 2

• Bile canulliculi = drain bile into the common hepatic duct
• Sinusoids = extremely permeable capillaries
• Hepatocytes = carry out a range of metabolic processes

Question 3

Functions of the liver

Answer 3

• Excretion of bilirubin, bile acids and urea
• Synthesis of proteins, lipids and glucose
• Detoxification of ammonia and toxins
• Storage of energy

Question 4

Acute liver disease

Answer 4

Occurs in response to an acute injury (physical or chemical)
Develops into fulminant hepatitis
Can be resolved if the offensive stimulus is removed

Question 5

Chronic liver disease

Answer 5

Occurs in responses to a sustained negative stimulus (viral, metabolic, autoimmune)
Inflammation is promoted, leading to fibrosis of the liver and culminating in cirrhosis

Question 6

Jaundice

Answer 6

The most obvious feature of liver disease and is seen as a yellowing of the skin and eyes

Question 7

Pre-hepatic jaundice

Answer 7

Occurs before the liver

Due to an overload of unconjugated bilirubin

Can be due to excessive erythocyte breakdown

Question 8

Hepatic jaundice

Answer 8

Occurs due to a disease affecting the liver itself

May be due to viral infections or drug overdoses

Question 9

Post-hepatic jaundice

Answer 9

Occurs after the liver

Due to a blockage in the biliary system

May also lead to fat malabsorption and vitamin deficiencies

Question 10

Portal hypertension

Answer 10

Seen in advanced liver disease

Occurs due to a build-up of pressure in the portal vein (over 12mmHg) which is occurs because blood has difficulty flowing through a cirrhosed liver

Question 11

Ascites

Answer 11

Ascites is an accumulation of fluid in the abdomen

A consequence of portal hypertension, because fluid is pushed into the peritoneal space

Question 12

Encephalopathy

Answer 12

A feature of very advanced liver disease

Biochemical disturbance of brain function due to toxic chemicals being unable to be metabolised by the liver

Symptoms = confusion, flapping tremor

Question 13

Albumin

Answer 13

Albumin levels are measured in LFTs as they reflect hepatic protein synthesis levels

Other diseases can also cause hypoalbuminaemia

Question 14

Alkaline phosphatase (ALP)

Answer 14

ALP levels are indicative of bile flow; ALP is released during cholestasis

Increases ALP levels can have causes other than liver disease

Question 15

Gamma glutamyltransferase (GGT)

Answer 15

GGT reflect bile flow and levels increase during cholestasis

Question 16

Transaminases

Answer 16

The transaminases ALT and AST reflect hepatocellular integrity

They are released in increased amounts if there is damage to hepatocytes

Question 17

Clinical uses of LFTs

Answer 17

• Detect the presence of liver disease
• Determine diagnostic category
• Establish disease severity
• Follow the progress of liver disease