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Transplant Surgery Liver Transplant Focus Note Hepatic (Liver) Basics Liver The liver is a soft, reddish-brown, “wedge-shaped” organ, weighing between 1.0 and 2.5 kg, located immediately under the diaphragm on the right side of the upper abdomen in front of the gallbladder and above the right kidney. It is the largest organ in the human abdomen and plays a major role in detoxification, glycogen storage and plasma protein synthesis. It also produces bile which is stored in the gall bladder. Fig. 1: Hilum through which the hepatic artery, portal vein and common bile duct pass. The liver is unique in that it is supplied by two major blood vessels: • Hepatic artery (20%); oxygenated blood from the celiac trunk • Portal vein (80%): delivers venous blood from the digestive tract so that nutrients can be processed in the liver and toxins extracted. The portal vein drains into the hepatic venous system which, in turn, drains into the inferior vena cava. The liver is the only internal human organ capable of natural regeneration of lost tissue. As little of 25% of remaining liver tissue can regenerate into a whole liver. Fig. 2: Hepatic vasculature divided into right and left sides. Gross Anatomy The liver is divided into four lobes based on surface features. On the front side a falciform ligament divides the liver into a left anatomical lobe, and a right anatomical lobe (Fig. 3). On the backside, there are two additional lobes between the right and left, the caudate and quadrate lobe. Functional Anatomy The central area of the liver where the common bile duct, portal vein and hepatic artery enter the liver is the hilum (porta hepatic) (Fig. 1). The common bile duct, portal vein and hepatic artery then divide into the left and right branches to supply the left and right lobes (Fig. 2). In a widely used Couinaud or French system, the functional lobes are further divided into a total of eight segments based on secondary and tertiary blood vessels. They are Caudate Lobe (1); Left Lobe (2) (3); Quadrate Lobe (4); Right Lobe (5)(6)(7) (8) (Fig. 4). Only 20% of an adult’s liver (Segments 2 & 3) is needed to serve as a liver allograft for an infant or small child. LiverTransplantBasics(Tx-2-fn)RevC2014USltr Fig. 3: Left and right anterior lobes of liver. Fig. 4: Functional segments of the liver. Hepatic (Liver) Basics cont. Why Is the Liver Important? Liver cells (hepatocytes) perform a variety of critical functions including: • producing and excreting bile used for food digestion. Some of the bile drains directly into the small intestine, and some is stored in the gallbladder. • metabolizes carbohydrates produces glucose from certain amino acids, lactate or glycerol. • breaks down insulin and other hormones • metabolizes lipids (fats): (synthesizes cholesterol, produces triglycerides) Fig. 5: Diseased cirrhotic (scarred) • produces coagulation essentials liver. Note the nodular • neutralizes toxins, medicinal products and hemoglobin transformation and • converts ammonia to urea irregular surface. • stores glucose, vitamin B12, iron, copper • breaks down hemoglobin of dead red blood cells and excretes it in bile Liver Diseases • Hepatitis: inflammation of the liver; Often characterized by jaundice (icterus) (yellowing of the skin & whites of the eyes, due to bilirubin buildup) • Cirrhosis: formation of fibrous tissue in the liver; caused by alcoholism or other toxins, or hepatitis (see Portal Hypertension below) • Hemochromatosis: hereditary disease resulting in the accumulation of iron • Wilson’s disease: hereditary disease in which the body retains copper • Cancer (hepatocellular carcinoma or cholangiocarcinoma) • Primary sclerosing cholangities, an inflammatory disease of the bile duct • Primary biliary cirrhosis, auto-immune disease of small bile ducts • Budd-Chiari syndrome, obstruction of the hepatic vein due to thrombosis (75%) or compression (25%). Portal Hypertension Less then 3% of the liver by weight is normally made up of collagenous (fibrous) material. However, as fibrosis increases in cirrhosis, a point is reached where portal pressure must increase in order to preserve flow. Hepatic portal hypertension contributes to fluid accumulation (ascites) in the peritoneal cavity by forcing more fluid across the liver capsule than the body is capable of draining. Sustained portal hypertension also causes enlargement of the spleen as well and the proliferation of collaterals which have the tendency to bleed and can divert blood away from the liver. REFERENCES ww.absoluteastromony.com/encyclopedia/l/li/kiver_transplantation.htm www.absoluteastromony.com/encyclopedia/a/al/allograft.htm www.transonic.com