Functions of liver and different liver function tests

Major functions of Liver are the following

1. Blood glucose regulation
2. Synthesis of glycogen
3. Synthesis of triacyl glycerol
4. Synthesis of plasma proteins
5. Detoxification
6. Bile production, helps in digestion
7. Bilirubin metabolism

Biochemical test are done to assess the following
The hepatic function 

To detect hepatic injury

Patterns of abnormalities are more important than single test

May be normal in proven liver disease

Normal value never rules out liver Disease

Classification of liver function test based on laboratory findings

Hepatic excretory function is assessed with following tests

Serum Bilirubin

Urine: Bile Pigments, bile salt, urobilinogen

Liver enzymes

ALT,AST,ALP,GGT,5’ nucleotidase

Synthetic Function

Total Proteins

Serum albumin, globulins

Prothrombin time

Special Test

Ceruloplasmin

Ferritin

Alpha1 antitrypsin

Alpha fetoProteins

Classification of liver function  based on clinical aspects

Markers of liver dysfunction

Serum Bilirubin

Urine: Bile pigments, bile salt, urobilinogen

Total proteins, albumin

Prothrombin time

Blood ammonia

Markers of hepato cellular Injury

ALT,AST

Markers of cholestasis

ALP

GGT

5’ Nucleotidase 

What is nonalcoholic fatty liver disease and what are its risk factors?

Definition of NAFLD 

This is a condition where patients having hepatic steatosis with or without inflammation and fibrosis, without any secondary causes of hepatic steatosis.

Following are the criteria for diagnosing nonalcoholic fatty liver disease

Imaging or biopsy should demonstrate  hepatic steatosis. 

Significant alcohol consumption  should be excluded.

Other causes of hepatic steatosis  should be  excluded.

What are the stages of NAFLD?

It include progression from steatosis, steatohepatitis to cirrhosis of liver

Steatosis ( Fatty liver )– NAFLD

Steatohepatitis – NASH

Cirrhosis

What are the disorders associated  with  NAFLD

Obesity

Systemic Hypertension

Hyperlipidemia

Insulin resistance or overt diabetes

PCOD

OSAS

Hypothyroidism

Hypopituitarism and hypogonadism

A family history of steatohepatitis or cryptogenic cirrhosis is  also implicated as a risk factor

Prevalence  of NAFLD

It is seen in 10-24% of general population.

2.6% of pediatric population have NAFLD.

It is the most common cause of cryptogenic cirrhosis

2/3rd of the obese patients have NASH.

90% of  morbidly obese patients have NASH.

Pathophysiology of ascites in Cirrhosis

There are numerous causes of ascites, the most common causes are

1. Malignant disease.

2. Cirrhosis.

3. Heart failure. 

Primary disorders of the peritoneum and visceral organs can cause ascites, and they should be considered even in those patients with chronic liver disease (CLD).

The main cause of ascites in cirrhosis is Splanchnic vasodilatation.It is mediated by vasodilators especially nitric oxide.These vasodilators are released when there is shunting of blood into the systemic circulation due to portal hypertension.As cirrhosis advances systemic arterial pressure falls due to severe splanchnic vasodilatation. 

This in turn leads to 

1. Activation of the RAS (renin–angiotensin system) with secondary aldosteronism.
2. Increased sympathetic nervous system activity.
3. Increased atrial natriuretic hormone secretion.
4. Altered activity of the kallikrein–kinin system.

These systems will try to normalise the arterial pressure but they result in salt and water retention.Combination of splanchnic arterial vasodilatation and portal hypertension tend to alter the intestinal capillary permeability, resulting in accumulation of fluid within the peritoneal cavity.