Liver (Anatomy and Function)

The liver's main job is to filter the blood coming from the digestive tract, before passing it to the rest of the body.

The liver has multiple functions. It makes many of the chemicals required by the body to function normally, breaks down and detoxifies substances in the body, and it also acts as a storage unit.

Hepatocytes (hepar=liver + cyte=cell) are responsible for making many of the proteins (protein synthesis) in the body that are required for many functions, including blood clotting factors, and albumin, required to maintain fluid within the circulation system. The liver is also responsible for manufacturing cholesterol and triglycerides. Carbohydrates are also produced in the liver and the organ is responsible for turning glucose into glycogen that can be stored both in the liver and in the muscle cells. The liver also makes bile which helps with food digestion.

The liver plays an important role in detoxifying the body by converting ammonia, a byproduct of metabolism in the body, into urea that is excreted in the urine by the kidneys. The liver also breaks down medications and drugs, including alcohol, and is responsible for breaking down insulin and other hormones in the body.

The liver also stores vitamins and chemicals that the body requires as building blocks. These include:

• Vitamin B12
• Folic acid
• Iron is required to make red blood cells
• Vitamin A for vision
• Vitamin D for calcium absorption
• Vitamin K helps the blood to clot properly

Is the liver a gland or an organ?

The liver is one of the vital organs of the body, responsible for hundreds of chemical actions that the body needs to survive. It is also a gland because it secretes chemicals that are used by other parts of the body. For these reasons the liver is both an organ and a gland; in fact, it is the largest internal organ in the body.

The liver is the largest internal organ of the body and is located in the right upper quadrant of the abdomen, beneath the diaphragm, and is protected by the lower right ribs.

The liver is divided into two lobes and has a rich blood supply obtained from two sources:

1. The portal vein delivers blood from the gastrointestinal tract (stomach, intestine, colon) and spleen
2. The hepatic artery supplies blood from the heart

The biliary tree describes a system of tubes that collect bile, help digest food, and drain it into the gallbladder or the intestine. Intrahepatic ducts are located inside the liver (intra=inside + hepar=liver) while extrahepatic ducts are located outside the liver.

Many diseases may affect the liver directly or as a consequence of an illness or disease that begins in another organ.

Fatty liver disease

• Fatty liver disease, caused by accumulation of cholesterol and triglycerides within the liver is not associated with alcohol abuse. Fatty liver disease is also referred to as nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH).
  • Nonalcoholic fatty liver disease (NAFLD). This condition affects your liver when there is excess fat but no damage. It is a silent disease that doesn't present any symptoms for years. Around 10%-20% of Americans will be diagnosed with this condition during their lifetime. Without making lifestyle changes to improve liver health, this disease may progress into NASH.
  • Nonalcoholic steatohepatitis (NASH). If your liver is inflamed and shows signs of cell damage, you may have NASH. Around 2%-5% of Americans will be diagnosed with this condition during their lifetime. Over time, damage results in permanent scars to your liver tissue, causing your liver to become hard and lose function. When your liver damage progresses to hardening, it is called cirrhosis.

Cirrhosis

• Cirrhosis of the liver describes a condition of scarring in the liver that is not reversible and may lead to liver failure.
• Alcohol abuse causes cirrhosis of the liver and is the most common cause of liver disease in North America.

Hepatitis

Hepatitis is an infection of the liver that causes liver inflammation.

• Hepatitis A is often spread by poor sanitary habits including poor handwashing and may be transmitted by food handlers. It tends to be self-limited.
• Hepatitis B and hepatitis C are spread by contact with infected body fluids.
• Hepatitis D is spread in conjunction with hepatitis B and needs the B virus for it to survive in the body and cause liver damage.
• Hepatitis E is a food or water-borne infection.

There are vaccinations available to prevent hepatitis A and hepatitis B.

Infections

Infections may affect the liver, including:

• Epstein Barr virus that causes infectious mononucleosis
• Adenovirus
• Cytomegalovirus
• Toxoplasmosis
• Rocky Mountain spotted fever

Medications or drug-induced liver inflammation

Liver inflammation is a relatively common side effect of medications. Some commonly prescribed medications include the following:

• acetaminophen over the counter (Tylenol, Panadol) but also in prescription pain medications (hydrocodone/acetaminophen (Lortab, Vicodin, Norco)
• Statins (medications used to control elevated blood cholesterol levels)
• Antibiotics (amoxicillin-clavulanic acid [Augmentin, Augmentin XR], nitrofurantoin [Macrodantin, Furadantin, Macrobid], tetracycline, isoniazid)
• methotrexate (Trexall, Rheumatrex)
• disulfiram (Antabuse)
• Herbal remedies, for example, kava kava, mahuang, comfrey

Toxins

• Poisonous mushrooms may damage the liver and cause liver failure.
• Alcohol in large doses can be toxic for the liver and damages the liver over time.
• Aflatoxins produced by certain fungi are toxic to the liver.
• Industrial chemicals may be toxins that affect the liver, such as arsenic and carbon tetrachloride.

Genetic disorders

Genetic disorders can affect the liver, examples include the following:

• Hemochromatosis with abnormal iron storage
• Wilson's Disease with abnormal copper storage
• Gilbert's Disease with abnormal bilirubin metabolism

Cancer

• Primary liver cancers arise directly from cells within the liver.
• Metastatic liver disease describes cancer that arises from another organ and invades the liver.

Abnormalities of bile flow from the liver

Abnormalities of bile flow from the liver may lead to liver inflammation, for example:

• Gallstones (the most common disease)
• Primary biliary cirrhosis
• Primary sclerosing cholangitis

Decrease in blood flow draining from the liver

A decrease in blood flow draining out of the liver may cause the liver to become congested and inflamed, two examples include:

• Congestive heart failure (CHF) is a condition in which the heart is not strong enough to pump all of the blood it receives, and that blood can back up into the liver.
• Budd Chiari syndrome is a disease in which blood clots form in the hepatic veins, preventing blood from leaving the liver.

Doctors aren't exactly sure what causes fatty liver disease, but there are some things these factors can put you at a higher risk:

• Obesity
• Excessive drinking
• High cholesterol levels
• Diabetes
• High blood pressure

Moderate drinking usually doesn't damage your liver. Men under the age of 65 can safely consume two to three servings of alcohol per day without liver damage. Men over the age of 65 should limit drinking to one beverage per day. Women can safely consume a single serving of alcohol per day without liver damage.

It is important to know the risk factors since fatty liver may not present symptoms in the early stages of the disease. Early identification is the key to reversing liver damage. Routine blood work is the most common way to diagnose a fatty liver.

Many different disease processes can occur in the liver.

The liver is a large organ and a significant amount of liver tissue needs to be damaged before a person experiences symptoms of disease. Symptoms also depend upon the type of liver disease.

• The inflammation of hepatitis may be associated with pain in the right upper quadrant of the abdomen, nausea, and vomiting. This may also be seen in people with gallstones.
• People may have jaundice (a yellow-orange hue to their skin) because the liver cannot metabolize bilirubin (the normal breakdown product of old red blood cells).
• There may be a tendency to bleed excessively or bruise easily because the liver is unable to manufacture blood clotting factors in adequate amounts.
• Fatigue, weakness, weight loss, and shortness of breath because of muscle wasting; due to the inability of the liver to manufacture proteins.
• Because the liver is involved in the metabolism of sex hormones, gynecomastia (enlarged breast tissue in men) and impotence may occur.
• In end-stage liver disease, ascites (fluid accumulation in the abdominal cavity), and leg swelling may occur because of inadequate production of albumin by the liver.
• There also may be difficulty in metabolizing ammonia causing its levels in the blood to rise, confusing due to encephalopathy (encephala=brain + pathy=dysfunction).

Healthcare professionals that diagnose and treat liver disease include:

• Diseases of the liver may be treated by primary care or internal medicine specialists.
• Gastroenterologists are specialists that focus on the digestive organs and liver.
• A hepatologist is a specialist focused exclusively on the liver.

Depending upon the exact type of liver disease, other specialists may be involved in the care of patients with liver disease, including infectious disease specialists, surgeons, oncologists, critical care specialists, hematologists, and emergency medicine specialists.

The liver is located in the abdomen but the health care professional will want to examine the whole body to look for the consequences of liver disease.

• The abdomen may be palpated to feel an enlarged liver. As it grows, the liver edge may be felt below the right rib margin. An inflamed liver in acute hepatitis may be tender but a liver that is cirrhotic, small, and shrunken, may not be able to be felt.
• If liver disease is a consideration, the health care professional also may feel for an enlarged spleen and assess whether excess fluid is present in the abdomen (ascites), perhaps indicating the presence of portal hypertension.
• The skin, including the sclera of the eyes, may be assessed for color looking for jaundice. Spider nevi, or angiomata, are a collection of blood vessels under the skin and may be normal, but in the proper setting may indicate liver disease.
• If the person is confused (hepatic encephalopathy), the doctor may attempt to elicit asterixis or flap on the physical examination. These people may not be able to keep their wrists cocked when their arms are held outstretched but instead see their wrists rhythmically flapping.
• Blood tests may be ordered to help make the diagnosis. Liver enzyme levels may reveal liver inflammation. However, in patients with end-stage liver disease, the liver can burn itself out and the enzymes may be normal even in the face of severe disease. Other blood tests that may be appropriate include a complete blood cell count (CBC), hepatitis virus screen, and blood clotting tests (a sensitive way to measure function since the liver is responsible for manufacturing the proteins involved in the blood clotting mechanism).
• On occasion, ultrasound may help assess the anatomy of the liver and this may lead to other tests including a CT scan to further assess the anatomy and structure of the liver and surrounding tissues.

Most often, diseases of the liver can be diagnosed by history, physical examination, and blood tests. On occasion, should the diagnosis be unclear or to assess the degree of damage to the liver, a liver biopsy may be necessary.

Using a very thin needle, a gastroenterologist or hepatologist (two types of liver specialists) or an interventional radiologist will insert a very fine needle through the skin and into the liver, to retrieve a small bit of tissue. This can then be examined under the microscope by a pathologist to help make the diagnosis. This procedure is done under sterile conditions to prevent infection, and a local anesthetic is injected into the skin to decrease the potential for pain.

If there is concern about only one area of the liver, instead of a disease that would affect the whole organ, an ultrasound may be used to help guide the needle into the proper position.

A liver transplant is a surgical procedure performed to remove a damaged or failed liver and replace it with a healthy liver. A liver transplant is usually only performed for severe, end-stage chronic liver disease, which can no longer be treated by other treatment options. The liver can be transplanted from a deceased donor with a healthy liver or a live donor, wherein a part of the liver is transplanted. The liver can regenerate fairly quickly in the live donor and the recipient. A single donated liver may even be used for two recipients.

Yes, you can donate a part of your liver without harming your health. The liver is the only organ in the body that can regenerate or grow back if a part of it is removed. When you donate a part of your liver, the part remaining in your body grows back in six to eight weeks. Also, the part transplanted will grow in the recipient. Within a week of the liver donation, the liver function returns to normal.

If you want to donate your liver, you will need to complete a qualifying phone interview. The interview is followed by a complete in-person evaluation that includes blood tests and medical imaging, such as ultrasound, computerized tomography scan, and magnetic resonance imaging.

To be eligible for the liver donation, you should:

• Be aged between 18 and 55 years of age. If the liver is to be donated to a child, the donor can be up to 60 years of age.
• Fit enough for surgery and recovery.
• Free from preexisting medical conditions, particularly the ones that affect bleeding or clotting.
• Do not use recreational drugs. Although smoking does not disqualify a donor, however, you must quit smoking as soon as possible before liver donation.
• Understand the psychological and physical risks involved.

The long-term success rates and survival rates following a liver transplant depend on the patient's condition. Usually, around 75% of people who undergo liver transplants live for at least 5 years.

What are the complications of liver transplant surgery?

Liver transplant surgery has a significant risk of complications, such as:

• Bleeding
• Blood clots
• Infection
• Rejection of the transplanted liver
• Failure of the transplanted liver
• Mental confusion
• Seizures
• Damage to the bile duct
• Bile duct leaks
• Recurrence of liver disease in the transplanted liver

It is not possible to live without a liver. Liver failure is a life-threatening condition that needs urgent medical intervention. If the liver function is compromised, such as liver failure, you can get serious complications, such as:

• Jaundice (yellowing of the eyes and skin)
• Tendency to bleed
• Infections
• Ascites (collection of fluid in the abdomen)
• Cerebral edema (excessive fluid in the brain)
• Kidney failure
• Altered consciousness (confusion, disorientation, sleepiness, and even coma)
• Fluid and electrolyte imbalance

It is possible to prevent liver disease through the following tips:

• Moderate alcohol consumption decreases the risk of the most common cause of liver disease in North America.
• The risk of contracting hepatitis B and hepatitis C can be decreased by minimizing exposure to body fluids.
• As mentioned previously, vaccinations are available for hepatitis A and B.
• Maintain a healthy weight and eat a balanced diet to decrease the risk of developing fatty liver disease.