2. Liver Ultrasound

Liver Pathology

Scanning the liver using ultrasound has many applications that are beyond the scope of this post. Here, we focus on the findings of acute hepatitis, cirrhosis, and fatty liver disease since they comprise the bulk of liver-related morbidity and mortality (Edlin, Scaglione).

Here is a quick table to help you differentiate between the different liver pathologies on ultrasound.

Acute hepatitis:Chronic hepatitis/cirrhosis:Fatty Liver Disease ( Hepatic Steatosis)
↑ Brightness of portal vein walls
↓ The echogenicity of the liver
Usually Enlarged Liver
↓ Brightness of portal vein walls
↑ Liver echogenicity
Usually Small/Atrophic Liver
↓ Brightness of portal vein walls
↑ Liver echogenicity
Usually enlarged Liver

However, the findings described here for hepatitis and cirrhosis are relatively uncommon findings in the general population and have uncertain operator-dependent sensitivities and specificities. Any ultrasound exam of the liver must be accompanied by a thorough history and physical exam, and inconclusive findings must be bolstered by additional diagnostic modalities.

Acute Hepatitis Ultrasound Findings

In the U.S. alone, over 3 million people have viral hepatitis (hepatitis C > hepatitis B), and over half of those people do not know they have the virus. What’s more, millennials currently represent the most commonly affected population, followed closely by baby boomers. (Office of Infectious Disease).

Acute hepatitis occurs when the liver has an inflammatory reaction to an injury, whether traumatic, infectious, drug-induced, or autoimmune (Joshi). This causes the liver to become edematous and enlarged.

Patients with acute hepatitis most frequently present with acute RUQ pain, fever, jaundice, and elevated liver enzymes (AST/ALT).

Hepatomegaly is the most sensitive POCUS finding in acute hepatitis, defined as a craniocaudal length ≥ 16.0 cm in the midclavicular line (Tchelepi). In addition, the liver may appear relatively hypoechoic versus the adjacent kidney, due to inflammatory fluid buildup in acute hepatitis. This causes the parenchyma to resemble a “starry sky” appearance, whereby the portal vein walls appear as hyperechoic “stars” on a background of dark, edematous hepatocytes. However, this finding has low sensitivity and specificity (Heller).

Edematous Acute Hepatitis Ultrasound Starry Sky Sign
Acute Hepatitis – Edematous Hypoechoic Liver with “Starry Sky” Sign

Cirrhosis Ultrasound Findings

Cirrhosis results from chronic damage to the liver. In the U.S., excessive alcohol consumption and chronic hepatitis C infection are the most common causes (Muzio). Over half a million Americans are estimated to have cirrhosis, although nearly 70% of them report not knowing they had liver disease. (Office of Infectious Disease).

Symptoms can include ascites, hepatosplenomegaly, jaundice, and dermatological findings such as palmar erythema or spider angiomas.

On ultrasound, you may find surface (capsular) nodularity (88% sensitivity, up to 95% specificity). In addition, the liver will be hyperechoic relative to the right kidney. Other, more difficult findings to assess include right lobe atrophy and caudate lobe hypertrophy (Arger). Keep in mind, however, that the liver may be enlarged in the early stages of cirrhosis, and you will not see atrophy until end-stage disease.

Cirrhotic Liver Ultrasound Hyperechoic
In cirrhosis, the liver becomes markedly hyperechoic relative to the kidney.

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