The Liver (view image)
The liver represents the largest gland of the body, lying beneath the diaphragm in the right upper abdomen (view location); it is of irregular shape and weighs from 1-2 kg, or about 1/40 the weight of the body. It receives a dual blood supply; approximately 20% of the blood flow is oxygen-rich blood from the hepatic artery, and 80% is nutrient-rich blood from the portal vein arising from the stomach, intestines, and spleen (view portal circulation diagram). The liver remains the only organ in the body that can regenerate after a portion has been removed. This regenerative capacity allows major resections to be performed--up to 75% of the liver. These types of resections can be performed provided the future liver remnant is not functionally compromised from other complex diseases such as hepatitis, cirrhosis, non-alcoholic or alcoholic liver disease. The distribution of the liver mass is maintained by a complex control mechanism in which bile flow, portal vein, and hepatic vein flows are the main regulators.The Liver Function
The liver functions as an exocrine gland. It secretes bile, initially receives most absorbed nutrients via the portal vein (view portal circulation diagram), detoxifies, stores glycogen, and is also of great importance in fat, carbohydrate, and protein metabolism. The majority of cells in the liver are hepatocytes, which constitute two-thirds of the mass of the liver. The remaining cell types are Kupffer cells (members of Hepatocytes perform numerous and vital roles in maintaining homeostasis and health. These functions include the synthesis of most essential serum proteins (albumin, carrier proteins, coagulation factors, many hormonal and growth factors), the production of bile and its carriers (bile acids, cholesterol, lecithin, phospholipids), the regulation of nutrients (glucose, glycogen, lipids, cholesterol, amino acids), and metabolism and conjugation of lipophilic compounds (bilirubin, cations, drugs) for excretion in the bile or urine.Diseases of the Liver
Fatty liver: Yellow discoloration of the liver due to fatty degeneration of liver parenchymal cells.Hepatitis: Inflammation of the liver, due usually to viral infection but sometimes to toxic agents.
Cirrhosis: Endstage liver disease characterized by diffuse damage to hepatic parenchymal cells, with nodular regeneration, fibrosis, and disturbance of normal architecture; associated with failure in the function of hepatic cells and interference with blood flow in the liver, frequently resulting in jaundice, portal hypertension, ascites, and ultimately biochemical and functional signs of hepatic failure.
What is a Liver Tumor?
Tumors are abnormal masses of tissue that form when cells begin to reproduce at an increased rate. The liver can grow both noncancerous (benign) and cancerous (malignant) tumors. Malignant tumors of the liver fall into two broad categories, those that start in the liver (primary tumors) and those that spread to the liver from other sites (secondary or metastatic tumors). The most common primary tumor of the liver is hepatocellular carcinoma, also known as hepatoma. This tumor typically occurs in patients with cirrhosis from chronic hepatitis or long-term alcohol use. Metastatic tumors to the liver can originate from many different types of cancer. Many of these tumors are treated with systemic chemotherapy, although there are cases where resection of the tumor or other liver-directed therapy can be curative. Two of the most common metastatic liver tumors that can be treated with liver-directed therapy include colorectal and neuroendocrine neoplasms.What Causes Liver Cancer?
Cancer develops when healthy liver cells become abnormal and grow too quickly. The abnormal cells form a mass called a tumor. When a tumor has the ability to spread to other parts of the body, it is called malignant. Another word for a malignant tumor is cancer. The exact cause of liver cancer is not known. Risk factors for primary liver cancer (hepatocellular carcinoma) include:- Viral hepatitis B and C
- Alcohol
- Cirrhosis
- Exposure to toxins
- Intake of anabolic steroids
- Non-alcoholic cirrhosis (fatty liver)
What are the Symptoms of Liver Cancer?
Many patients do not experience symptoms; the cancer is discovered during routine follow-up tests for a previous cancer outside of the liver, or during diagnostic testing for the presence of cirrhosis or viral hepatitis B or C. Symptoms of liver cancer may include:Pain: Pain, although rarely associated with liver cancer, may be located on the right side of the upper abdomen, in the right shoulder, or in the back. The primary cause of this pain is the stretching of the liver capsule.
Fever: Fever is always a possible sign of infection. Fever, without infection, is occasionally associated with liver cancer.
Jaundice: Jaundice shows up as yellow skin and eyes, dark urine, and light colored stool. Jaundice occurs when a substance called bilirubin builds up in the blood. Bilirubin is made in the liver to help with fat metabolism and then travels down the bile duct just before emptying into the duodenum, a section of the small intestine. If a large amount of the liver is replaced by tumor, or if bile duct obstruction occurs, bilirubin builds up in the blood. This buildup causes a person to become noticeably yellow, or jaundiced. The other signs of jaundice are a change in stool color (stools become white) and a change in urine color. Itching can occur when bilirubin builds up in the blood. Obstructed (blocked) bile ducts can increase the risk of infection, including sepsis (infection in the blood).
Indigestion, lack of appetite, nausea, and weight loss: These symptoms can occur when a liver tumor presses against the stomach and small intestine. Problems with digestion may also occur for complex reasons not specifically related to the location of the tumor.
Abdominal or leg swelling: Abdominal fluid (ascites) can build up in the setting of chronic (long-standing) liver disease. It may be accompanied by swelling of the legs. Abdominal and leg swelling can also be caused by other illnesses such as heart or kidney disease. Liver cancers can be associated with ascites (abdominal fluid). This fluid can be removed temporarily with a needle (paracentesis) or sometimes can be controlled with diuretics (fluid pills).
Types of Non-cancerous Liver Tumors
Noncancerous (benign) tumors are quite common and are usually without symptoms. Often they are not diagnosed until an ultrasound, CT scan, or MRI is performed. There are several types of benign tumors, including:
Hemangioma (view image): This type of benign tumor is the most common tumor found in the liver. They are a mass of abnormal blood vessels. Up to five percent of adults have small liver hemangiomas that cause no symptoms. Treatment is usually not required. Sometimes infants with large liver hemangiomas require surgery to prevent clotting and heart failure.
Focal Nodular Hyperplasia (view image): Are benign tumors that occur primarily in women of age 20-30 years old. They are the second most common tumors of the liver after hemangiomas. They usually present as a single mass and have no malignant potential. Treatment is usually performed for patients because of symptoms or size.
Hepatocellular Adenoma: This benign tumor occurs most often in women of childbearing age. Most of these tumors remain undetected. Sometimes an adenoma will rupture and bleed into the abdominal cavity, requiring surgery. Rarely does an adenoma turn cancerous.
