Category: 2. Liver Ultrasound

Fatty liver disease or Hepatic Steatosis is a common cause of abdominal pain and elevated liver function test enzymes.

Fatty liver disease can be associated with alcohol abuse, diabetes, obesity, hyperlipidemia, medications (amiodarone, methotrexate, chemotherapy), pregnancy, metabolic disorders, etc.

Hepatic Steatosis ultrasound findings include (Khov 2014):

• Increased liver echogenicity (fat appears echogenic on ultrasound).
• May have enlarged liver size.
• The Renal cortex appears relatively hypoechoic when compared to the liver (the kidney cortex and liver are usually isoechoic).

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).

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.

Using the lateral ultrasound approach, you can assess the size, texture (parenchymal echogenicity), and surface characteristics (capsular contour) of the liver (Rumack). Importantly from this view, the liver also offers a useful acoustic window to view clinically important structures such as the aorta, IVC, hepatic veins, and portal vein.

Position your probe on the patient’s right in the mid-axillary line at the 10th-11th intercostal space, with the indicator facing the patient’s head. If possible, ask your patient to hold their right arm above their head to widen the intercostal spaces.

Visualize the diaphragm, liver, and right kidney in the long-axis.

• Tip: if the ribs are blocking a good view, ask the patient to hold a deep breath to further widen the intercostal spaces. Try rotating your probe obliquely to align with the intercostal spaces as well.

Assess the liver’s echogenicity and capsular contour.

• Normally, the liver has a homogenous echogenicity similar in brightness to the renal cortex (Rumack). Check for notable variations, such as increased or decreased echogenicity, masses, or lesions.
• The liver should have a smooth capsular contour, again similar to that of the kidney. Note any marked coarseness or nodularity.

Measure the liver span in the craniocaudal dimension.

• Once you have visualized the structures listed above, freeze the image and measure the liver span from the diaphragmatic surface to the inferior border, as pictured below.
• Tip: sometimes, the ultrasound window is too narrow to capture the liver’s diaphragmatic surface and tip together on the screen. Estimate, to the best of your ability, where either of these surfaces would end if you could see them both, and place your calipers at your best guess.

You can use point of care ultrasound of the liver when you encounter a patient with right upper quadrant (RUQ) pain and acute changes in liver function tests.

For the purposes of this abdominal ultrasound guide, the most important measurement to keep in mind is the craniocaudal length of the right lobe. Although liver size varies considerably from patient to patient, depending on age, sex, habitus, and other factors, a healthy liver should be < 16cm in this dimension. This corresponds to roughly the 5th – 11th right intercostal spaces.