Liver Function Tests (LFTs)

Liver Function Tests (LFTs)

• LFTs are lab tests used to analyze liver performance under normal and diseased conditions.

Aspartate Aminotransferase (AST)

• Elevated levels can indicate cirrhosis, hepatitis, hepatic necrosis, and obstructive disease.

Alanine Aminotransferase (ALT)

• More specific than AST for evaluating liver function.
• Remains elevated longer than AST.
• Elevated levels can indicate cirrhosis, hepatitis, pancreatitis, and biliary obstruction.

Alkaline Phosphatase (ALP)

• Marked elevation is associated with obstructive jaundice, hepatic carcinoma, abscess, or cirrhosis.

Alpha-Fetoprotein

• A protein normally synthesized by the liver, yolk sac, and GI tract of a fetus.
• Increased levels can indicate hepatocellular carcinoma, liver metastasis, and hepatoblastoma in childhood.

Lactic Acid Dehydrogenase (LDH)

• Mildly elevated in hepatitis, cirrhosis, and obstructive jaundice.

Gamma Glutamyl Transpeptidase (GGT)

• Increased in diseases that cause acute damage to the liver and bile ducts.

Prothrombin Time (PT)

• It measures the time in seconds for blood to coagulate, with a normal clotting time of 10 to 15 seconds.
• Prothrombin time is prolonged in the presence of liver disease with cellular damage.

Serum Albumin

• A decrease suggests a decrease in protein synthesis.

Bilirubin

• A product of hemoglobin breakdown in red blood cells.
• Excessive red blood cell destruction or liver cell malfunction causes a rise in serum bilirubin, leading to jaundice.

Indirect Bilirubin (Unconjugated Bilirubin)

• Elevated levels are seen with increased red blood cell destruction (anemias), associating with non-obstructive conditions.

Direct Bilirubin (Conjugated Bilirubin)

• Elevated levels are usually related to obstructive jaundice, such as from stones or neoplasms obstructing ducts.

Diffuse Liver Disease

• Affects the functional cells of the liver (hepatocytes) and decreases liver function.
• Treated medically rather than surgically and are measured through liver function tests.
• Diffuse parenchymal diseases include fatty infiltration, acute and chronic hepatitis, alcoholic liver disease, and cirrhosis.

Fatty Liver Disease (Hepatic Steatosis)

• An acquired reversible disease characterized by fat deposits within the liver cells.
• Common causes of fatty liver include obesity, alcohol abuse, and diabetes mellitus.
• Other causes include chemotherapy, pregnancy, and glycogen storage disease.
• Patients are typically asymptomatic, but some may present with jaundice, nausea, vomiting, and abdominal pain with elevated liver function tests.

Diffuse Fatty Infiltration

• Causes the liver to appear diffusely echogenic and becomes more difficult to penetrate during imaging.
• Comparison of liver parenchyma to the kidney is useful in determining if fatty infiltration is present.
• Walls of hepatic vasculature and diaphragm will not be easily imaged due to sound beam attenuation.

Focal Fatty Infiltration

• It causes the affected liver segment to appear as an area of increased echogenicity, resembling a solid, hyperechoic mass.
• More difficult to diagnose, as it may resemble mass lesions.

Focal Fatty Sparing

• Involves areas of the liver spared from fatty infiltration when the entire liver isn't affected.
• These spared areas show decreased echogenicity within the fatty echogenic liver.
• Typically seen in the gallbladder fossa, adjacent to the porta hepatis or right portal vein, and the left medial segment of the left lobe.

Hepatitis

• Defined as inflammation of the liver that can lead to cirrhosis, portal hypertension, and hepatocellular carcinoma
• It is a result from infections (i.e. viral, bacterial) or non-infectious conditions (medication, toxins, autoimmune disorders).
• Can be acute or chronic and comes in many forms (A, B, C, D, E, and G).
• Types A, B, and C are the most common.
• Healthcare workers need to be especially aware of their risk for contracting Hepatitis B and C.
• Symptoms include fever, chills, nausea, vomiting, fatigue, hepatosplenomegaly, dark urine, and jaundice.
• May result in elevation of ALT, AST, conjugated and unconjugated bilirubin.

Hepatitis A

• Is a contagious liver disease resulting from infection with the hepatitis A virus.
• Can range in severity from mild to severe.
• Usually spread when a person ingests fecal matter from contaminated food or drinks.

Hepatitis B

• Typically spread through blood, semen, or other body fluids via sexual contact or sharing needles/syringes.
• Can also be passed from an infected mother to her infant at birth.
• Chronic hepatitis B can increase the risk of developing cirrhosis or hepatoma.

Hepatitis C

• Usually spread by blood.
• Can be either acute or chronic.
• Chronic hepatitis C can lead to long-term health problems or death.

Acute Hepatitis (Sonographic Findings)

• The liver often appears normal in echo texture but may be enlarged and show decreased echogenicity.
• Over time, the liver and spleen can enlarge.
• Periportal cuffing (thickening of portal vein walls) may be noted, with walls appearing more hyperechoic, resulting in a "starry sky" appearance.
• Gallbladder wall may be thickened and prominent due to fluid accumulation within hepatocytes.

Chronic Hepatitis

• Exists when there is clinical or biochemical evidence of hepatic inflammation that extends beyond 6 months.
• The liver texture becomes coarse and hyperechoic with decreased brightness of portal triads, but attenuation is not as great as in fatty infiltration.
• The liver does not increase in size or may be small in size.
• Fibrosis may be evident, producing "soft shadowing" posteriorly.

Cirrhosis

• Defined as hepatocyte death, fibrosis, and necrosis of the liver, with the development of regenerating nodules.
• The process is chronic and progressive.
• Leads to liver cell failure and portal hypertension as the end stage.
• Micronodular, most commonly from chronic alcohol abuse.
• Macronodular caused by chronic viral hepatitis or other infections.
• Alcoholic liver disease is the predominant cause of cirrhosis in the United States.
• Clinical presentation includes hepatomegaly, jaundice, and ascites.
• Abnormal liver function tests include elevated AST, ALT, GGT, LDH, and conjugated bilirubin.

Cirrhosis (Sonographic Findings)

• In early stages, hepatomegaly is the first finding.
• In advanced stages, the liver's right lobe decreases in size (small liver in chronic stage).
• Increased echogenicity and coarsening of hepatic parenchyma secondary to fibrosis.
• The caudate lobe is often spared (hypertrophied) and may appear normal in echogenicity.
• Fatty infiltration causes increased attenuation with decreased vascular markings.
• Hepatosplenomegaly may occur with ascites surrounding the liver.
• Chronic cirrhosis shows surface nodularity, which is more evident with ascites.
• Nodules are typically hypoechoic compared to the surrounding liver, yet are not seen due to the small size.

Portal Hypertension

• It is the elevation of blood pressure within the portal venous system above 10 mmHg, with a normal pressure of 5 to 10 mmHg.
• The most common cause is cirrhosis.
• Can also result from portal vein thrombosis or compression by a tumor in an adjacent organ.
• With cirrhosis, the liver becomes fibrotic and difficult to perfuse, increasing pressure within the portal veins.
• Can be asymptomatic, patients may present with sudden, painless, upper GI hemorrhage due to rupture of esophageal varices, ascites, hepatomegaly, jaundice, and abnormal liver function tests
• Caput Medusa (tortuous collaterals around the umbilicus) may be present.
• Sonographic findings include secondary signs like splenomegaly, ascites, and portal systemic venous collaterals.
• Abnormal blood flow patterns can cause the development of collaterals and varicosities.
• One of the most identified collaterals is the recanalization of the paraumbilical vein.
• Abdominal varicosities may be noted near the splenic hilum, renal hilum, and the gastroesophageal junction.
• The hepatic artery increases its supply to the liver.
• The portal vein diameter will exceed 13 mm in the anteroposterior dimension.
• Irregular, stagnant flow can increase the likelihood of portal vein thrombosis.
• May eventually demonstrate reversed flow within the portal vein, termed hepatofugal(away from the liver).

Transjugular Intrahepatic Portal-Systemic Shunt (TIPS)

• Created to relieve portal hypertension, avoiding development or rupture of gastroesophageal varices.
• Placement involves a stent between right portal and hepatic veins to shunt blood (bypassing the liver and returning directly to the IVC), thereby reducing portal systemic pressure.
• Only a temporary treatment for portal hypertension.
• A TIPS has strong echogenic walls and an anechoic lumen.
• Pulsed Doppler examination of a normal functioning TIPS demonstrates flow toward the IVC with an average velocity of 100 to 190 cm/s.
• Flow with a velocity of less than 90 cm/s indicates decreased flow through the stent, potentially from thrombosis.
• Flow velocities of more than 190 cm/s indicate high-grade stenosis within the shunt.
• Color Doppler can confirm patency and direction of flow (hepatopetal in MPV, hepatofugal in RPV and LPV with patent TIPS).

Portal Vein Thrombosis

• It is the development of clot within the portal vein.
• Seen in conditions like hepatocellular carcinoma, pancreatic carcinoma, metastasis, portal hypertension, pancreatitis, cholecystitis, pregnancy, oral contraceptive use, inflammatory bowel disease, cirrhosis, hepatitis, and trauma.
• Thrombus can completely occlude the portal vein, leading to the development of collaterals within the portal vein region.
• This results in a mesh of tiny blood vessels (cavernous formation of the portal vein).
• Patients may present with abdominal pain, low-grade fever, leukocytosis, hypovolemia, elevated LFTs, nausea, and vomiting.
• Sonographic findings: Initially, a blood clot may be hard to visualize due to its isoechoic nature. With time, the thrombus becomes more echogenic.
• Increase portal vein caliber
• Cavernous transformation of Portal systemic collaterals

Budd-Chiari Syndrome

• A condition characterized by the occlusion of the hepatic veins, possibly coexisting with an occlusion of the inferior vena cava. It can be secondary to coagulation abnormalities, tumor invasion, thrombosis, oral contraceptive use, pregnancy, and trauma.
• Clinical symptoms include ascites, right upper quadrant pain, hepatomegaly, and possibly splenomegaly.
• Sonographic features include nonvisualization of hepatic veins, thrombus within hepatic veins, enlarged caudate lobe, no lack of flow within hepatic veins with color Doppler, and narrowing of the inferior vena cava.