Liver ultrasound: complete guide from preparation to interpretation

Liver ultrasound, also called ‘liver sonography’, is one of the most frequently done exams in diagnostic medical imaging. Because of its non-invasive nature, nevertheless, it has the ability to take real-time images and is used as an initial imaging modality.

What is a liver ultrasound?

Additionally, liver ultrasound is one of the most frequently performed abdominal examinations and is often the first imaging modality that is employed to assess liver disease. However, to acquire diagnostic images, it is important to know the normal liver anatomy and the important sonographic landmarks.

Therefore, here is an easy-to-follow guide to the structure of the liver.

Surface anatomy of the liver:

The liver is the largest solid organ, and the liver is located in the right upper quadrant (RUQ). However, part of the liver is extended into the epigastric region’s left upper quadrant, particularly the left lobe. Moreover, it is located under the diaphragm and covered by ribs.

Consequently, most of the liver is hidden behind the rib cage, so during liver ultrasound, intercostal scanning is often necessary.

Patient preparation for liver ultrasound:

So, patient preparation is essential for taking good-quality images and proper diagnosis.

• Ideally, to reduce interference from bowel gas, the patient should ideally fast for at least six hours before a liver ultrasound scan.
• Additionally, sonographers used greyscale B-mode imaging for routine evaluation, with Doppler studies added if needed.

Patient position for liver ultrasound:

Therefore, when performing routine liver ultrasound, patient positioning is also essential for better imaging:

Standard positions for liver ultrasound:

for routine ultrasound examinations

• supine position
• right arm raised above the head

These positions widens the intercostal spaces and provide optimal acoustic window

When to use alternative positions?

If visualisations are suboptimal, the following positions may improve image quality:

• left lateral decubitus
• slightly left posterior oblique

Probe Selection

A general, Curvilinear Probe (2–5 MHz) is used

Ideal for:

• for assessing liver examination

visulization of imaging hepatic structures

• for adult patients

Alternatively, a phased array probe is used

Useful for:

•   Intercostal windows

•   Bedside and POCUS examinations

Meanwhile, the linear probe (7–12 MHz) can be

Useful for:

•  Superficial lesions • Paediatric imaging

•  Detailed vascular evaluation

Scanning technique for liver ultrasound:

So, for liver ultrasound, follow this:

• Start with an extensive sweep of the liver to begin with.
• Next, ask the patient to take deep breaths to completely visualise the superior borders of the liver.
• Then, using a subcostal approach, look up and down the left lobe in the transverse direction.
• Afterward, examine the right lobe in the subcostal or intercostal approach.
• Additionally, carefully roll the patient onto their left side and assess the Rt lobe after checking for fluid.
• However, during a subcostal approach, the liver may be obscured by bowel gas, and it may be necessary to have the patient distend their abdomen in order to get a better picture.
• Alternatively, the intercostal approach may be used between the ribs and can also be a good way to ensure good visualisation.

Scanning approach for liver ultrasound:

The following guideline should be included in complete liver examinations: Together, they provide the comprehensive evaluation of the liver and surrounding vascular structure.

I-Subcostal View: However, this is obtained through placing the probe just below the right ribcage and angling it upward beneath the diaphragm.

Best for:

• Left lobe
• Portal vein
• Hepatic veins
• Porta hepatis

ii – Intercostal View: nevertheless, this is obtaining when bowel gas or rib cage block the standard subcostal view; then it provides the best window for visualization of right lobe

Additionally, ask the patient to hold their breath; this pushes the liver below the ribcage. As a result, it provides the best image.

Therefore, best for:

• Hepatic dome
• next, right lobe
• Additionally, segments VII and VIII.

iii – Sagittal Plane: shows the long axis of the liver. Moreover, it shows the relationship of the liver with vascular structures.

Therefore, its shows:

• First, the long axis of the liver

• Then, inferior vena cava (IVC)
• Hepatorenal interface

iv-Transverse Plane

Demonstrates:

• First, Portal bifurcation

however, right and left lobes

•  and Hepatic veins

Normal Liver Echotexture

If liver is slightly brighter then kidney then look for steatosis ( fatty liver)

Therefore, a normal liver shows the following sonographic features:

• Homogenous parenchymal echogenicity
• Smooth borders
• Liver normal size less than 17 cm

Liver lobes on ultrasound:

The liver is divided into the right lobe, the left lobe and the caudate lobe. However, knowledge of these lobes is of great importance for the correct ultrasound examination and localization of lesions.

Therefore, it includes the following:

Right lobe on liver ultrasound:

is the largest portion of the liver. however , its includes

• Segments V, VI, VII and VIII

Moreover, we can access the right lobe with an intercostal approach.

Left lobe on liver ultrasound:

is located in the epigastric region. However, it contains

• Segments II, III and  IV

Moreover, we can access the left lobe with a subxiphoid approach.

Caudate lobe

In this we can access segment I.

Therefore, found anterior to the IVC and posterior to the portal vein.

Sonographic landmarks

so , identifying sonographic landmarks are essential for accurate diagnosis

Portal Vein in Liver Ultrasound:

Therefore, among all the vascular structures, the portal vein is the most important landmark

Sono-appearances

• Thick echogenic walls
• Branches into right and left portal veins

Remember: moreover, starry appearances on liver parenchyma

Hepatic veins in liver ultrasound:

However, hepatic veins consist of the following:

• Right hepatic vein
• Middle hepatic vein
• Left hepatic vein

Sono appearances:

Therefore, it appears on ultrasound:

• Thin walls
• Toward IVC

 

The portal vein and hepatic veins drain into the IVC.

Sono appearances

• Thick walls
• Presented vertically and with respiration-change caliber

Ligamentum Teres

however ,it Is remnant of umbilical vein

Sono appearance

• Echogenic band  in left lobe
• It’s a landmark for the identifying segment IV

Couinaud segments simplified

Therefore, for anatomical localization liver is divided into eight segments

Segment I

In this caudate lobe is present

Segment -II and III

Left lateral lobe (left of hepatic vein and falciform ligament)

Segment IV

Left medial lobe (between left and middle hepatic veins)

4a- superior (above)

4b-inferior (below)

Segment V and VIII

 Right anterior section

V is located below and VIII I located above the portal plane between middle and right hepatic veins

Memory trick: Clockwise from left lobe II-III-IV-V-VI-VIII

Segment VI and VII

Right posterior section

Normal Measurements

Structure	Normal Size
Liver length	<15–16 cm
Portal vein	<13 mm
Common bile duct	<6 mm
IVC	Variable
Hepatic artery	<7 mm

Frequently asked questions (FAQs)

Is liver ultrasound used for a variety of reasons?

yes, It is used to assess fatty liver, cirrhosis, liver enlargement, masses and other liver diseases.

Is it necessary to have an ultrasound of the liver before fasting?

Yes, it is usually recommended to fast for 6-8 hours to get better images.

Is liver ultrasound painful?

Not at all, liver ultrasound is safe, painless and non-invasive.

Can liver ultrasound be used to detect fatty liver?

Yes, fatty liver changes are often detected by ultrasound.

On ultrasound, what is the normal size of the liver?

The liver is normally about 15–16 cm long in adults.

Does Doppler play a role in liver ultrasound?

The Doppler can be used to evaluate blood flow in the vessels of the liver.