Liver Ultrasound Imaging

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Questions and Answers

What is the frequency range of ultrasound waves?

50 kHz to 100 kHz

Over 20 kHz (correct)

20 kHz to 50 kHz

Less than 20 kHz

How are ultrasound waves generated?

By a thermoelectric transducer

By a photovoltaic transducer

By a magnetostrictive transducer

By a piezoelectric transducer (correct)

What is the function of a piezoelectric transducer in ultrasound?

It converts electrical signals into mechanical waves and vice versa (correct)

It only receives reflected ultrasound waves

It only transmits ultrasound waves

It amplifies the reflected ultrasound pulses

In A-mode ultrasound, how are the echoes displayed?

As peaks with measurable distances between structures Signup and view all the answers

What is the most sensitive modality for the detection of membranes, septa and hydatid sand in hydatid cysts?

Ultrasound Signup and view all the answers

Which feature on ultrasound may indicate a haemangioma in the liver?

Posterior acoustic enhancement with acoustic shadowing Signup and view all the answers

What is the main complication of hepatic hydatid?

Cyst rupture Signup and view all the answers

What may result in internal echoes in a cyst, resembling an abscess or necrotic tumor?

Hemorrhage or infection Signup and view all the answers

What is the most important clinical problem in distinguishing a regenerative nodule from a small hepatocellular carcinoma on liver ultrasonography?

$5$ mm size threshold Signup and view all the answers

What imaging method is used most frequently to screen for liver tumors due to its noninvasive and inexpensive nature?

$Ultrasound$ Signup and view all the answers

What may be indicated by multiple spherical cystic masses with varying sizes, completely echo-free with a sharp outline and posterior acoustic enhancement?

Echinococcal cyst Signup and view all the answers

What does ultrasound have >90% sensitivity for diagnosing in hydatid cysts?

Echinococcal cyst Signup and view all the answers

What can be very difficult to differentiate from hydatid disease?

Cystic focal liver lesions Signup and view all the answers

What imaging modality is valuable to differentiate cystic from solid lesions in liver tumors?

Ultrasound Signup and view all the answers

What type of ultrasound images depict all the tissue traversed by the scan?

B-mode images Signup and view all the answers

Which mode displays motion as a wavy line and is commonly used for cardiac ultrasound?

M-mode Signup and view all the answers

What is acoustic enhancement?

Increased echogenicity of tissues Signup and view all the answers

What is acoustic shadowing?

Decreased echogenicity of tissues Signup and view all the answers

What is an acoustic window?

A tissue or structure that offers little obstruction to ultrasound waves and serves as a route to image deeper structures. Signup and view all the answers

What is a cyst?

A fluid-filled structure with thin walls and anechoic content. Signup and view all the answers

What are debris in ultrasound imaging?

Solid masses within a fluid-filled mass, which are echogenic and may be mobile. Signup and view all the answers

What do hyperechoic tissues do?

Create brighter echoes than adjacent tissues. Signup and view all the answers

What do hypoechoic tissues do?

Create dimmer echoes than adjacent tissues. Signup and view all the answers

What are internal echoes in ultrasound imaging?

Ultrasound reflections from tissues of different density within an organ. Signup and view all the answers

Which type of liver lesion is typically discovered incidentally and is almost always asymptomatic?

Simple hepatic cyst Signup and view all the answers

What is the composition of true hepatic cysts?

Serous fluid and cuboidal epithelium Signup and view all the answers

Sonographically, how does a well-defined solitary cyst in the liver appear?

Echo-free with posterior acoustic enhancement Signup and view all the answers

What condition may exhibit an enlarged liver with a non-homogeneous pattern and increased echogenicity in the liver parenchyma?

Congestive cardiac failure Signup and view all the answers

What condition is associated with small or shrunken liver, portal hypertension, splenomegaly, and ascites?

Macronodular cirrhosis Signup and view all the answers

What may be consistent with multiple echogenic masses in the liver, without discrete masses?

Hepatocellular carcinoma Signup and view all the answers

Study Notes

B-mode images are two-dimensional, real-time ultrasound images that depict all the tissue traversed by the scan.
Real-time mode shows motion by displaying changing images in real time as the transducer is moved.
M-mode displays motion as a wavy line and is commonly used for cardiac ultrasound.
Acoustic enhancement is the increased echogenicity (echo brightness) of tissues that lie behind structures that cause minimal ultrasound wave attenuation.
Acoustic shadowing is the decreased echogenicity of tissues that lie behind structures that cause significant ultrasound wave attenuation.
An acoustic window is a tissue or structure that offers little obstruction to ultrasound waves and serves as a route to image deeper structures.
A cyst is a fluid-filled structure with thin walls and anechoic (echo-free) content, which may have strong back wall reflections and enhancement of echoes behind the cyst.
Debris are solid masses within a fluid-filled mass, which are echogenic and may be mobile, changing with the patient's position or movement.
Hyperechoic tissues create brighter echoes than adjacent tissues, such as bone, perirenal fat, and gallbladder wall.
Hypoechoic tissues create dimmer echoes than adjacent tissues, such as lymph nodes, some tumors, and fluid.
Internal echoes are ultrasound reflections from tissues of different density within an organ, such as gallstones or debris.
Ultrasound is a valuable tool for assessing liver size, texture, and functional status, as well as for identifying possible liver lesions and checking the patency of hepatic and portal veins.
Ultrasound indications include enlarged liver, suspected liver abscess, jaundice, abdominal trauma, ascites, suspected metastases, suspected liver mass, right upper abdominal pain, and screening for endemic echinococcosis.
In a normal liver, the parenchyma appears homogeneous, with portal vein and branches as linear tubular structures with reflective walls. The hepatic veins are non-reflective, and it should be possible to follow them to their confluence with the inferior vena cava.
The hepatic veins can be made to dilate with the Valsalva maneuver, and the inferior vena cava and aorta may be identified.
The liver is composed of right and left lobes, as well as the caudate lobe, which is limited posteriorly by the inferior vena cava. The gallbladder, a pear-shaped, echo-free structure, and the right kidney must also be identified.
The echogenicity of the normal liver parenchyma lies midway between that of the pancreas (more echogenic) and the spleen (less echogenic).
Simple hepatic cysts are common benign liver lesions, occurring in 5%-7% of the population. They are typically discovered incidentally and are almost always asymptomatic.
Simple hepatic cysts may be isolated or multiple, and vary from a few millimeters to several centimeters in diameter. They do not communicate with the biliary tree and have no malignant potential.
The origin of true hepatic cysts is believed to be hamartomatous tissue. They are composed of serous fluid and lined by cuboidal epithelium identical to that of bile ducts.
Sonographically, a well-defined solitary cyst appears as a rounded, echo-free mass with acoustic enhancement. It is usually less than 3 cm in diameter. Small hydatid cysts cannot always be differentiated sonographically.
Large or enlarged liver with homogeneous pattern:
- Congestive cardiac failure: hepatic veins dilated, inferior vena cava does not vary on respiration, and pleural effusion above the diaphragm.
- Acute hepatitis: liver enlargement and tenderness with no characteristic sonographic changes.
- Tropical hepatomegaly: liver enlargement and splenomegaly.
- Schistosomiasis: either sonographically normal or enlarged liver with thickening of the portal vein and main branches.
Large or enlarged liver with non-homogeneous pattern:
- Without discrete masses: increased echogenicity in the liver parenchyma, loss of highly reflective edges of the peripheral portal veins, and cirrhosis, chronic hepatitis, or a fatty liver.
- With multiple echogenic masses: various sizes, shapes, and echo textures, and may be consistent with macronodular cirrhosis, multiple abscesses, multiple metastases, or multinodular hepatocarcinoma.
Small or shrunken liver: micronodular cirrhosis, associated with portal hypertension, splenomegaly, ascites, and dilated splenic veins, and may be difficult to diagnose in the early stages.
Sonographic features of multiple echogenic masses in the liver: various sizes, shapes, and echo textures, and may be consistent with macronodular cirrhosis, multiple abscesses, multiple metastases, or multinodular hepatocarcinoma. It is not possible to distinguish between lymphoma and metastases by ultrasound.
Haemorrhagic cysts: irregular in outline, and may exhibit acoustic enhancement. However, once the blood has clotted, the haematomas may be hyperechogenic. It is important to obtain a clinical history of trauma or anticoagulant medication.

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Description

Test your knowledge of liver ultrasound imaging with this quiz. Identify and interpret oblique and transverse scans of the liver, including the portal and hepatic veins, inferior vena cava, and patterns associated with hepatic abnormalities.