ALCOHOL AND LIVER DISEASE

 

Figure 1.Notice the placement of the liver in the body, it fills the upper right abdominal cavity.

Liver:Function

The liver is a complex organ that is necessary for life.†† It is the largest gland in the body and the second largest organ.The liver is about 1/50 of a personís weight.It fills the upper right abdominal cavity and lies against the colon, right kidney and small intestines.It is divisible into four lobes containing liver cells and Kupfferís cells (specialized cells in the liver which filter bacteria and other small foreign proteins out of the liver).

The Liverís Functions:

The liver receives almost all the blood flow from the digestive tract; thus, when you drink alcohol which is absorbed directly into the bloodstream, the liver is going to receive most of it and is going to have to break it down and try to rid your body of this poison.The normal blood flow into the liveris approximately 1.5 liters per minute.

*Breaks down toxins absorbed from the intestine or manufactured in the body and modifies them so they are no longer harmful; then it excretes them into bile or blood.

*†† Stores vitamins, especially fat-soluble vitamins.

*†† Synthesizes cholesterol, metabolizes or stores sugars, and processes fats.

*†† Assembles amino acids into various proteins.

*†† Controls blood fluidity and regulates blood-clotting mechanisms.

*†† Converts the products of protein metabolism into urea for excretion by the kidneys, which will leave your body as urine.

*†† Stores minerals such as iron for red blood cell production.

 

Liver:Alcohol Induced Disease

*The connection between heavy alcohol consumption and liver disease has been recognized for more than 200 years.

*Because your liver is so large and has the capacity to regenerate, people can function with only 10-20% of their liver; the symptoms of liver disease will not be prevalent until you have progressed substantially into the disease (see figure 1).

Figure 1.Notice the difference between a healthy liver and a liver with cirrhosis.

*Symptoms may remain latent until damage is really detrimental!

*The minimum dose of alcohol that must be consumed for serious liver injury to become apparent in men is 5-6 standard drinks daily for 20 years.For women, the minimum dose is one-fourth to one-half that amount.

*No more than one-half of heavy drinkers develop alcoholic hepatitis and cirrhosis. Thus, other risk factors must play a role in the development of alcohol-related liver complications.

*Risk factors for alcoholic hepatitis and cirrhosis are:

        Gender

        Heredity

        Diet

        Co-occurring liver illness

 

 

 

Liver:Three Types of Alcohol Induced Damage

 

 

Three conditions of the liver are often associated with alcohol abuse.Liver disease in alcoholics usually progresses through the three conditions chronologically starting with fatty liver and proceeding to alcoholic hepatitis which can eventually lead to cirrhosis.

 

 

*†† Fatty Liver:Fat deposits in the liver.To some extent, fat deposits will happen in almost all heavy drinkers.It can also happen in non-alcoholics after just one incidence of drinking.

Symptoms:People with fatty liver may have no symptoms and have just an abnormal enlargement of the liver that is smooth and non-tender with minimal or no functional changes.However, alcoholics may have

        Abdominal pain

        Severe jaundice syndrome(a yellow discoloration of the skin, mucus membranes, and white part around the eyes caused by greater than normal amounts of bilirubin in the blood)

        Acute liver failure

        Ascites (abnormal accumulation of fluid containing proteins and electrolytes and causing an abnormal swelling in the abdomen)

        Coma

        Death.

Outcome:Chances of recovery are better at this stage than with cirrhosis.Damage is reversible and does not necessarily lead to more serious damage.

*†† Alcoholic Hepatitis:Widespread inflammation and destruction of liver tissue.Patients may develop fibrosis, where scar tissue begins to replace healthy liver tissue.

Symptoms:Fever, jaundice, and abdominal pain.

Outcome:May be fatal but also may be reversed by abstaining from alcohol.

Frequency:Occurs in 50% of heavy drinkers.

 

Figure 2.Alcoholic liver: Cut surface of gross autopsy specimen of liver showing unnatural paleness due to a dense network of scar tissue (fibrosis, cirrhosis). Scarring has occurred in response to chronic injury from alcohol abuse.

*†† Alcoholic cirrhosis:(see figure 2) Most advanced form of liver disease, 15-30 percent of heavy drinkers.

Early Symptoms: General weakness, weight loss.

Later Symptoms:Loss of appetite, indigestion, nausea, vomiting, abdominal swelling, and spider nevi (spidery red marks on upper body arms and face).Causes extensive fibrosis that stiffens blood vessels and distorts the internal structure of the liver.Functions of the liver may be impaired which may lead to malfunction of other organs such as the brain and kidneys.

Outcome:Usually fatal due to complications such as kidney failure, and hypertension (high blood pressure) in the vein carrying blood to the liver.This disease is usually fatal if chronic alcohol exposure continues; however, if the patient quits drinking, their condition may become stable.

Frequency:Statistics from different populations vary because of varying lifestyles; however, statistics show that between 40-90% of the 26,000 annual deaths from cirrhosis are alcohol-related.

 

*†† The alcoholic will progress from fatty liver to alcoholic hepatitis, to cirrhosis.Sometimes heavy drinkers may develop alcoholic cirrhosis without first developing alcoholic hepatitis, and it could also happen that an alcoholic may have a sudden onset and rapid course of alcoholic hepatitis; then die before cirrhosis develops.

Not all liver disease in alcoholics is caused by alcohol.Also, alcohol induced liver disease may be accompanied by other conditions not related to alcohol but which can cause liver failure, such as nonalcoholic hepatitis and exposure to drugs and occupational chemicals.Furthermore, it is important to remember that fatty liver and alcoholic hepatitis may be reversed if you stop drinking alcohol, and cirrhosis can be stabilized if you stop drinking alcohol.

Metabolism of Alcohol in the Liver:

*†† Most of alcohol that people drink is metabolized in the liver.

*†† Alcohol dehydrogenase (ADH):This is the enzyme that converts alcohol to acetaldehyde through a chemical process called oxidation.

*†† The chemical, acetaldehyde, which is generated, is more toxic than alcohol itself.

*†† Aldehyde dehydrogenase converts acetaldehyde to acetate, which can be used as fuel by the cell.

*†† Acetate travels through the bloodstream to other parts of the body where it can enter other metabolic cycles that produce energy or useful molecules. The usual biological role of both ADH and ALDH is to metabolize vitamin A.

*†† Studies have shown that women, Asians, Native Americans, and older people have less of the enzyme alcohol dehydrogenase; thus they are not able to metabolize alcohol as efficiently as those who have more of this enzyme possibly making them get drunk faster and experience liver complications sooner.

*†† In people who engage in heavier and more chronic alcohol consumption, a second pathway is utilized with the enzyme called microsomal ethanol-oxidizing system (MEOS).

*†† MEOS helps get rid of toxic compound in the body by using an enzyme called cytochrome P450 This enzyme converts alcohol to acetaldehyde.

*†† Cytochrome P450 is thought to help eliminate alcohol at high blood alcohol concentrations that prevail in heavy drinkers.

*†† Cytochrome P450 also generates reactive oxygen radicals that damage cellular components.

*Chronic alcohol consumption can substantially increase iron levels in the body.In fact almost one third of alcoholics have excessive iron levels in their livers much of which is free iron; thus these elevated levels may damage liver.††

*Some acetaldehyde may combine with liver proteins to form harmful compounds that can impair the function of various cellular components and enzymes.††

*†† Also alcohol can combine with other molecules in the cell to form potentially dangerous compounds such as fatty acid ethyl esters and phosphatidylethanol.††

 

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