SA CHAPTER 9

What causes biliary obstruction distal to the cystic duct?

A biliary obstruction distal to the cystic duct may be caused by stones in the common duct, an extrahepatic mass in the porta hepatis, or stricture of the common duct. Clinically, common duct stones cause RUQ pain, jaundice, pruritus, and an increase in direct bilirubin and alkaline phosphatase. On ultrasound examination, the dilated intrahepatic ducts are seen in the periphery of the liver. The size of the gallbladder is variable, but it is usually small. Gallstones often are present and appear as hyperechoic lesions along the posterior floor of the gallbladder, with a sharp posterior acoustic shadow. Careful evaluation of the common duct may show stones within the dilated duct.

What is the composition of bile?

Bile is composed of 97% water, bile salts and pigments, and inorganic salts (sodium chloride and sodium bicarbonate)

. What causes biliary obstruction proximal to the cystic duct?

Biliary obstruction proximal to the cystic duct can be caused by carcinoma of the common bile duct, or metastatic tumor invasion of the porta hepatis. Clinically the patient may be jaundiced and may experience pruritus (itching). The liver function tests show an elevation in the direct bilirubin and alkaline phosphatase levels. On ultrasound, carcinoma of the common bile duct appears as a tubular branching with dilated intrahepatic ducts that are best seen in the periphery of the liver. It may be difficult to image a discrete mass lesion. The gallbladder is of normal size, even after a fatty meal is administered.

Name the common causes of fatty liver.

Common causes of fatty liver include the following: alcoholic liver disease, diabetes mellitus, obesity, severe hepatitis, chronic illness, and steroids.

. How does diffuse hepatocellular disease affect the hepatocytes in the liver?

Diffuse hepatocellular disease affects the hepatocytes and interferes with liver function. The hepatocyte is a parenchymal liver cell that performs all the functions ascribed to the liver. A measurement of this abnormality is done through a series of liver function tests. The hepatic enzyme levels are elevated with cell necrosis. With cholestasis (interruption in the flow of bile through any part of the biliary system, from the liver to the duodenum), the alkaline phosphatase and direct bilirubin levels increase. Likewise, when there are defects in protein synthesis, there may be elevated serum bilirubin levels and decreased serum albumin and clotting factor levels.

What is the effect of fatty infiltration on the liver?

Fatty infiltration implies increased lipid accumulation in the hepatocytes and is the result of significant injury to the liver or a systemic disorder leading to impaired or excessive metabolism of fat. Fatty infiltration is a benign process and may be reversible.

Describe the difference between acute and chronic hepatitis.

In acute hepatitis, damage to the liver may range from a mild disease to massive necrosis and liver failure. Hepatosplenomegaly is present, and the gallbladder wall is thickened. Chronic hepatitis exists when there is clinical or biochemical evidence of hepatic inflammation for at least 3 to 6 months. Chronic persistent hepatitis is a benign, self-limiting process. Chronic active hepatitis usually progresses to cirrhosis and liver failure.

Describe the ultrasound appearance of fatty infiltration of the liver.

Moderate to severe fatty infiltration shows increased echogenicity on ultrasound examination. Enlargement of the lobe affected by the fatty infiltration is evident. Visualization of the portal vein structures may be difficult because of the increased attenuation of the ultrasound. Thus it becomes more difficult to see the outline of the portal vein and hepatic vein borders.

Describe the clinical findings in a patient with hepatitis

Patients with hepatitis may present initially with flu and gastrointestinal symptoms, including loss of appetite, nausea and vomiting, and fatigue. Jaundice may occur in severe cases. Laboratory values show abnormal liver function tests, with increases in the ALT, AST, and bilirubin.

What is the metabolic physiology of carbohydrates in the liver?

Simple sugars freely enter the liver cells, where they are converted to glucose. The glucose pool in the liver can be easily exchanged with that in the blood. (Only the liver can actually release glucose: when the blood glucose is low, the liver releases glucose into the blood; when the glucose level is high, the liver cells take up and store glucose.)

Discuss the sonographic findings of a cirrhotic liver.

Specific findings may show course texture of the liver parenchyma secondary to fibrosis and nodularity. Increased attenuation may be present, with decreased vascular markings. Hepatosplenomegaly may be present, with ascites surrounding the liver. Chronic cirrhosis may show nodularity of the liver surfaces, especially if ascites is present. The hepatic fissures may be accentuated. The isoechoic regenerating nodules may be seen throughout the liver parenchyma.

Describe the role of amino acids within the liver.

The amino acids within the liver cells form a pool that can be used to make the various proteins of the liver and blood as well as glucose, fats, and energy. The amino acids can be exchanged with a second similar pool in the blood, which in turn exchanges amino acids with a third pool within the tissue cells. The liver is a major center for the synthesis and degradation of amino acids and proteins. The liver forms and secretes most of the blood proteins. Ammonia is formed during the deamination of amino acids. Ammonia can be toxic to the liver or other tissues. The liver detoxifies ammonia by converting it into urea, which is a water-soluble substance.

How does the blood leave the liver?

The blood leaves the liver via the hepatic veins into the inferior vena cava.

Describe the complications of cirrhosis of the liver.

The essential features of cirrhosis are simultaneous parenchymal necrosis, regeneration, and diffuse fibrosis, resulting in disorganization of lobular architecture. The disease process is chronic and progressive, with liver cell failure and portal hypertension as the end stage. Cirrhosis is most commonly the result of chronic alcohol abuse but can be the result of nutritional deprivation, hepatitis, or other infection.

What does an ultrasound evaluation of the liver parenchyma include?

The evaluation of the liver parenchyma includes the assessment of its size, configuration, homogeneity, and contour examined in a supine, right anterior oblique position in a transverse, coronal, subcostal oblique, and sagittal view to completely survey the organ.

Trace the path of bile after the hepatocytes form bile in the liver.

The hepatocytes form bile and secrete it into small canaliculi, which coalesce to form the bile ducts. In these ducts, bile flows in the opposite direction of arterial blood to prevent mixing. The bile ducts coalesce to form the hepatic duct, which emerges from the liver. The hepatic duct bifurcates to form the cystic duct, which leads to the gallbladder and the common bile duct. Together with the pancreatic duct, they empty into the duodenum.

Describe the pathway of the blood as it flows into the liver

The incoming arterial blood and portal blood are mixed as they flow into the liver sinusoids. The hepatocytes take oxygen and nutrients from this blood, and then the blood flows into the hepatic veins

What is the name given to liver cells?

The liver cells are called hepatocytes and are packed in the walls of cells that are separated by blood sinusoids.

. Discuss the role of fat metabolism in the liver.

The liver is capable of forming, degrading, and storing fats. It has the ability to achieve metabolic interconversion among fats, carbohydrates, and proteins. The liver (through fat metabolism) can make cholesterol and form ketone bodies.

. What role does the liver play in the hormonal regulation of blood sugar?

The liver is the major organ regulating the balance of blood sugar and carbohydrate metabolism. The liver has enzymes that convert glycogen to glucose, glycerol to glucose, and vice versa, and amino acids to glucose and the reverse. The liver cannot synthesize glucose from fatty acids. Through the portal vein, the liver has direct access to the carbohydrates absorbed from the intestine, which makes it the center for the synthesis, delivery, storage, and production of glucose. The liver has a special enzyme to free glucose and is the only organ that can secrete glucose into the blood when the level of this substance exceeds the blood level. The liver helps to maintain a steady state of glucose in the bloodstream

Name the two sources that supply blood to the liver

The liver receives blood from two sources: the hepatic artery and the portal vein.

. What diseases cause an elevation of both direct and indirect bilirubin?

Total bilirubin is the elevation of both direct (conjugated) and indirect (unconjugated) bilirubin levels in hepatic metastasis, hepatitis, lymphoma, cholestasis secondary to drugs, and cirrhosis, but the increase in the direct level is more marked