AbScan Liver Review

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

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 the 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 diseases cause an elevation of both direct and indirect bilirubin?

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

Name the three basic types of abscess formation in the liver

intrahepatic, subhepatic, and subphrenic.

What is the definition of a neoplasm?

neoplasm is any new growth of new tissue, either benign or malignant. If the neoplasm is benign, growth occurs locally, but does not spread or invade surrounding structures. A malignant mass is uncontrolled and is prone to metastasize to nearby or distant structures via the bloodstream and lymph nodes.

What is the function of the sphincter of Oddi?

regulates bile flow from the common bile duct into the duodenum. When this sphincter is closed, the bile accumulates in the common bile duct, flowing back into the cystic duct and gallbladder, where it is stored temporarily. After meals, the gallbladder contracts, releasing bile into the duodenum

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 are the clinical symptoms and sonographic findings of a liver adenoma?

A liver adenoma is found more commonly in women Patients may have right upper quadrant pain secondary to rupture, with bleeding into the tumor. There is increased incidence in patients with Type I glycogen storage disease or von Gierke's disease. On ultrasound examination, the mass may look similar to focal nodular hyperplasia. It is hyperechoic with a central hypoechoic area caused by hemorrhage. The lesion may be solitary or multiple. If the lesion ruptures, fluid should be found in the peritoneal cavity

Describe the characteristic findings of an amebic abscess

An amebic abscess is a collection of pus formed by disintegrated tissue in a cavity, usually in the liver, caused by the protozoan parasite Entamoeba histolytica. Patients may be asymptomatic or have gastrointestinal symptoms such as abdominal pain, diarrhea, leukocytosis, and low fever. The ultrasound appearance of amebic abscess is variable and nonspecific. The abscess may be round or oval and may have a lack of significantly defined wall echoes. The lesion is hypoechoic compared with normal liver parenchyma and may show low-level echoes at higher sensitivity. There may be some internal echoes along the posterior margin secondary to debris. Distal enhancement may be seen beyond the lesion

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.

Describe the findings of a cavernous hemangioma

Cavernous hemangioma is the most common benign tumor of the liver. Hemangiomas enlarge slowly and undergo degeneration, fibrosis, and calcification. They are found in the subcapsular hepatic parenchyma or in the posterior right lobe more often than in the left lobe of the liver. The ultrasound appearance of hemangioma is typical in that most are hyperechoic with acoustic enhancement. They are either round, oval, or lobulated, with well-defined borders. The larger hemangiomas may have a mixed pattern as a result of necrosis. The hemangioma may become more heterogeneous as it undergoes degeneration and fibrous replacement. It also may project with calcifications, which appear as complex or anechoic echo patterns.

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 sonographic findings and incidence of focal nodular hyperplasia

Focal nodular hyperplasia lesions occur in the right lobe of the liver. There may be more than one mass; many are located along the subcapsular area of the liver; some are pedunculated; and many have a central scar. On ultrasound examination, the lesions appear well defined and show hyperechoic to isoechoic patterns as compared with the liver. The internal linear echoes may be seen within the lesions if multiple nodules are together.

What complications may arise after liver transplant?

Hepatic artery thrombosis is the most serious complication of liver transplantation. Postoperatively, evaluation of the hepatic artery is made with Doppler and color flow ultrasound in the area of the porta hepatis. The normal hepatic artery flow is a low-resistance arterial signal. Thrombosis may be detected when there is absence of this signal. In the adult patient, the development of collateral vessels in the region of the hepatic artery is absent. However, in children, collateral formation of hepatic artery circulation may be present. Thus the scans should be made within 24 and 48 hours postoperatively and weekly thereafter to assess for change in velocity flow pattern. The development of anastomotic stenoses is another problem that may occur in the transplant patient. The flow pattern of this complication shows a turbulent, high-velocity signal indicative of hepatic artery stenosis. Portal vein thrombosis also may occur in the postoperative period. Air in the portal vein may be seen as bright, echogenic moving targets within the portal venous system. Compromise of the IVC is another complication of transplantation. A fatal complication is hepatic necrosis associated with thrombosis of the hepatic artery or portal vein. Massive necrosis takes the forms of gangrene of the liver and air in the hepatic parenchyma.

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.

What are the clinical findings in a patient with portal hypertension?

In hypertension, clinically the patient presents with ascites, hepatosplenomegaly, gastrointestinal bleeding, elevated liver enzymes, jaundice, and hematemesis

What are the clinical and sonographic findings of metastatic liver disease?

In metastatic liver disease, clinically the patient has hepatomegaly, abnormal liver function tests, weight loss, and decreased appetite. It is typical for this disease to occur in multiple nodes throughout both lobes of the liver. The ultrasound patterns of metastatic tumor involvement in the liver vary. Three specific patterns have been described: 1. well-defined hypoechoic mass; 2. well-defined echogenic mass; and 3. diffuse distortion of normal homogeneous parenchymal pattern without focal mass. The hypovascular lesions produce hypoechoic patterns in the liver as a result of necrosis and ischemic areas from neoplastic thrombosis. Most cases of hypervascular lesions correspond to hyperechoic patterns.

Describe the ultrasound appearance of an echinococcal cyst of the liver

On ultrasound examination, several patterns may occur, from a simple cyst to a complex mass with acoustic enhancement. The shape of the cyst may be oval or spherical, and may have regularity of the walls. Calcifications may occur. Septations are very frequent (e.g., honeycomb appearance with fluid collections); water lily sign, which shows a detachment and collapse of the germinal layer; or cyst within a cyst. Sometimes the liver may contain multiple parent cysts in both lobes of the liver; the cyst with the thick walls occupies a different part of the liver. The tissue between the cysts indicates that each cyst is a separate parent cyst and not a daughter cyst. If a daughter cyst is found, it is specific for echinococcal disease.

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. Lab values show abnormal liver function tests, with increases in the ASP, AST, and bilirubin

Describe the appearance of lymphoma of the liver.

Patients with lymphoma of the liver have hepatomegaly, with a normal or diffuse alteration of parenchymal echoes. A focal hypoechoic mass may be seen sometimes. The presence of splenomegaly or retroperitoneal nodes may help confirm the diagnosis of lymphadenopathy. Hodgkin's lymphoma appears with hypoechoic and diffuse ultrasound patterns in the liver. Non-Hodgkin's lymphoma may appear with target and echogenic mass lesions.

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 coarsening 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 edge, especially if ascites is present. The hepatic fissures may be accentuated. The isoechoic regenerating nodules may be seen throughout the liver parenchyma. Portal hypertension may be present with or without abnormal Doppler flow patterns. Patients who have cirrhosis have an increased incidence of developing hepatoma tumors within the liver parenchyma

Discuss the three patterns of hepatocellular carcinoma

The carcinoma may appear in one of three patterns: as a solitary massive tumor, multiple nodules throughout the liver, or diffuse infiltrative masses in the liver. All of the patterns cause hepatomegaly. The carcinoma can be very invasive and is seen to invade the hepatic veins to produce Budd-Chiari syndrome. The portal venous system also may be invaded with tumor or thrombosis. The hepatocellular carcinoma has a tendency to destroy the portal venous radicle walls with invasion into the lumen of the vessel.

Discuss the development of collateral circulation.

The development of collateral circulation occurs when the normal venous channels become obstructed. This diverted blood flow causes embryologic channels to reopen; blood flows hepatofugally (away from the liver) and is diverted into collateral vessels. The collateral channels may be the gastric veins (coronary veins); esophageal veins; recanalized umbilical veins; and splenorenal, gastrorenal, retroperitoneal, hemorrhoidal, and intestinal veins. The most common collateral pathways are through the coronary and esophageal veins, which is the case in 80% to 90% of patients with portal hypertension. Varices, tortuous dilations of veins, may develop because of increased pressure in the portal vein, usually secondary to cirrhosis. Bleeding from the varices occurs with increased pressure.

Discuss the development of portal venous hypertension and its effects on the hepatic system

The development of increased pressure in the portal splenic venous system is the cause of portal hypertension. The hypertension develops when hepatopetal flow (toward the liver) is impeded by thrombus or tumor invasion. The blood becomes obstructed as it passes through the liver to the hepatic veins and is diverted to collateral pathways in the upper abdomen. There are two ways portal hypertension may develop. One is through increased resistance to flow, and the other is in increased portal blood flow. The most common mechanism for increased resistance to flow occurs in patients with cirrhosis. Patients who have increased portal blood flow may have an arteriovenous fistula or splenomegaly secondary to a hematologic disorder

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

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

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. This gives the liver the unique roles of glucose exchanger and Glucostat

Discuss the incidence and findings of liver trauma

The liver is the third most common organ injured in the abdomen after the spleen and kidney. Laceration of the liver occurs in 3% of trauma patients and is frequently associated with other injured organs. The need for surgery is determined by the size of the laceration, amount of hemoperitoneum, and patient's clinical status. The right lobe is affected more often than the left. The degree of trauma is variable and may include small lacerations, large lacerations with hematomas, subcapsular hematomas, or capsular disruptions. Intraperitoneal fluid should be assessed along the flanks and into the pelvis

Name the primary sites that cause metastatic disease to spread to the liver

The primary sites of metastatic disease are found in the colon, breast, and lung. The majority of metastases arise from a primary colon or from an HCC

What is a recanalized umbilical vein?

The umbilical vein may become recanalized secondary to portal hypertension. This vessel is best seen on the longitudinal plane near the midline, as a tubular structure coursing posterior to the medial surface of the left lobe of the liver. On transverse scans, a bulls-eye pattern is seen within the ligamentum teres as the enlarged umbilical vein.

Discuss the various portal caval shunts available and what considerations the sonographer should have before the examination.

There are basically three types of shunts: the portacaval, mesocaval, and splenorenal. The portacaval shunt attaches the main portal vein at the superior mesenteric vein-splenic vein confluence to the anterior aspect of the IVC. The mesocaval shunt attaches the middistal superior mesenteric vein to the IVC. This shunt may be difficult to image if overlying bowel gas is present. The splenorenal shunt attaches the splenic vein to the left renal vein. The shunt and connecting vessel should be documented with real-time, pulsed Doppler, and color Doppler to determine flow patterns and patency.

What is the role of ultrasound in liver transplantation?

Ultrasound examination can play a significant role in the preoperative and postoperative evaluation of hepatic transplantation. The primary function of the ultrasound examination is the evaluation of the portal venous system, the hepatic artery and veins, the IVC, and the liver parenchymal pattern. The vascular structures should be assessed for their size and patency in the preoperative evaluation. The examination of the liver parenchyma should be made to rule out the presence of hepatic architecture disruption. The sonographer should also evaluate the biliary system to look for dilation and evaluate the portosystemic collateral vessels.

Name the common causes of fatty liver

alcoholic liver disease, diabetes mellitus, obesity, severe hepatitis, chronic illness, and steroids

Describe the role of amino acids within the liver.

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

the 2 sources that supply blood to the liver

hepatic artery and the portal vein

How does the blood leave the liver?

hepatic vein.

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

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 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

What is the composition of bile?

water, bile salts and pigments, and inorganic salts (sodium chloride and sodium bicarbonate). All of these elements are produced by liver cells. Bile salts (or acids) are formed from cholesterol within the hepatocytes. To form bile pigments, bilirubin, which is the metabolite of heme formed during red blood cell destruction, is taken up from the blood and conjugated to glucuronic acids to form the yellow bilirubin glucuronide