Sonography Degree: Diffuse Liver Disease
Published: January 13, 2011
Sonographs are often used to detect liver problems. Diffuse parenchymal liver disease has distinct features when observed with a sonograph however most features are nonspecific. The most typical causes of liver disease are fatty infiltration, early alcoholic liver disease, acute hepatitis, chronic hepatitis and cirrhosis. The appearance of fatty infiltration or early alcoholic liver disease can improve rapidly on a sonograph when the primary cause is treated or removed.
The liver can become enlarged with fatty infiltration. When this occurs, echogenicity increases and it becomes difficult to visualize the right hemidiaphragm and blood vessels within the liver. The best way to determine the extent of fatty infiltration is to compare the liver echogenicity to the right renal parenchyma. Liver parenchyma is usually, under normal circumstances, only slightly more echogenic then the kidneys. The spleen is also slightly more echogenic than the liver. If the echogenicity between the liver and right kidney is greater than between the spleen and right kidney then fatty infiltration may be the cause. Severe fatty infiltration can make it extremely difficult to penetrate more than a few centimeters of the liver and completely obstruct any posterior structures.
Early Alcoholic Liver Disease
Alocholic liver disease is often indicated by the subtle changes in the liver's shape. The edge of the right lobe of the liver usually becomes rounded and a large lobe or prominate caudate lobe may be seen. Echogenicity also increases and cirrhosis eventually occurs, causing the liver to shrink and become dense.
More common in men than in women, hepatitis is an inflammation of the liver that is often caused by viral infection. There are six forms of hepatitis. The nonviral causes of acute hepatitis include drug toxicity and wild mushroom poisoning.
When acute hepatitis is a problem, the portal triads become more prominent and diffuse swelling causes the liver to have a "stary sky" appearance. This swelling also causes the liver to have decreased echogenicity. The liver and spleen often become enlarged and the gallbladder wall can become thickened. However, when observing by ultrasound it is possible that the liver will appear normal.
Hepatitis B and C (HVB and HVC) are the both linked to chronic hepatitis and cirrhosis. Hepatitis C is the most important liver disease in the United States because it produces chronic liver infections. More than 4 million Americans are infected and more than 10,000 people die each year from HVC infection.
On an ultrasound, chronic hepatitis can appear to be normal. As soon as cirrhosis develops it can become easier to see a difference in the livers appearance. Cirrhosis causes the liver to become small and the echotexture to become coarse, secondary to fibrosis.
Chornic hepatitis is being successfully treated by combining weekly injections of interferon and ribavirin, an oral antiviral drug.
Cirrhosis is a progressive chronic inflammation of the liver that usually occurs from chronic alcoholism or severe chornic hepatitis. It is caused by the rapid regeneration of connective scar tissue that regenerates faster then damaged hepatocytes. This causes the liver to become fatty and fibrous. When the liver develops cirrhosis it becomes smaller, hyperechoic, and begins to develop a nodular border. As the disease progresses, the liver will become atrophied and very echogenic. Advanced cases may have portal hypertension. The paraumbilical vein may become recanalized. This will be evident by sonograph if a dilated vein is seen running from the left portal vein back to the umbilicus. Other collateral vessels may be seen in the prota hepatic and the splenic hilum. The connecting veins are small and can burst when forced to carry large volumes of blood. Signs of their failure include vomiting blood, and a snakelike network of destended veins surrounding the naval. Swollen veins in the esophagus and ascites as well as an accumulation of fluid in the peritoneal cavity are additional complications of portal hypertension.
If the cause of the cirrhosis is treated quickly and early, the parenchyma may be able to regenerate any areas that were not too badly damaged. This regeneration is a slow process that will occur over time and can usually be seen in the focal and hypoechoic areas within the liver.
Liver transplants are the only clinically proven effective treatment for patients with end-stage liver disease. Unfortunately, donor organs are scarce and many patients die while waiting for a suitable organ. If someone is fortunate to find a suitable organ in time there is a one-and-five-year survival rate for this type of transplant.