Liver ultrasonography (synonyms: ultrasound of the liver; liver ultrasound) is a noninvasive diagnostic procedure in radiology and internal medicine that can be used to clarify pathologic (pathological) processes as a routine examination or when a specific question is raised. Sonographic evaluation of the liver, gallbladder, and bile ducts is usually the primary diagnostic procedure in the evaluation of organ systems. Because of this, the significance of liver sonography is critical to the correct selection of diagnostic procedures that follow sonography. Hence, this results in the importance of liver sonography for “setting the course” in the diagnosis of pathologic processes of the liver.
Indications (areas of application)
- Control examinations and tumor evaluation – as a rule, sonographically diagnosed findings represent incidental findings, because liver sonography is the primary procedure for liver diagnostics. Thus, the procedure is the procedure of choice in the case of palpation findings (palpation findings) or liver-associated symptoms. In the case of a known tumor disease, liver sonography is used to exclude a recurrence.
- Elevated liver enzymes – an increase in liver enzymes, which include alanine aminotransferase (ALT, GPT), aspartate aminotransferase (AST, GOT), gamma-glutamyl transferase (γ-GT, gamma-GT; GGT), indicates liver damage. However, the increase in enzymes is a non-specific parameter.
- Lesion of the gallbladder and bile ducts – analogous to liver sonography, sonography is also used as the first diagnostic procedure for possible pathological processes of the biliary system (e.g., cholestasis/bile stasis). Color-coded Doppler sonography (FKDS) is also used in the evaluation of neoplasms (tumors).
- Liver cirrhosis (shrunken liver), chronic hepatitis B virus infection or non-alcoholic fatty liver hepatitis [bi-annual B-scan sonography to monitor for HCC].
- Suspicion of space occupying lesions (tumor?)
- Sonography screening in high-risk patients for hepatocellular carcinoma (HCC; primary hepatocellular carcinoma) [biannual B-scan sonography].
- Hepatomegaly (liver enlargement) – enlargement of the liver can be accurately detected with sonography.
- Icterus (jaundice) – damage to the liver with additional functional impairment can lead to the development of icterus.
- Ascites (abdominal fluid) – ascites is the accumulation of fluid in the abdominal cavity. The fluid is either a protein- and cell-poor transsudate (clear fluid) or, in the case of a blood outflow disorder, a more cell-rich exudate (turbid fluid). Both cardiac and liver-specific and other pathogeneses (causes of disease) are possible as causes.
Contraindications
There are no known contraindications. If an allergic adverse reaction is known to occur when the contrast agent is ingested, do not perform contrast-enhanced sonography.
The procedure
Liver sonography represents a versatile procedure; however, the sensitivity of the procedure (percentage of diseased patients in whom the disease is detected by the use of the procedure, i.e., a positive finding occurs) varies depending on the experience of the examiner and the pathologic process present. Due to this, variations from 20 to 90% can be observed in the accuracy of the ultrasound procedure. However, the development of additional methods based on the use of ultrasound has further improved its effectiveness. The power Doppler method can be mentioned as an example of such a development. By using this method, it is possible to achieve significantly better contrast imaging by using so-called “harmonic imaging”. Furthermore, the use of special intravascular ultrasound contrast agents enables a precise assessment of the liver vessels. Conventional liver ultrasonography
- In conventional liver sonography, the assessment is performed using the so-called B-scan technique (B-scan ultrasonography).Due to the wide application and value in diagnostics, this method has been reviewed in terms of performance in various clinical studies, so that the sensitivity of the method could be accurately evaluated.
- The extension of conventional liver sonography by the use of “Tissue Harmonic Imaging” has the consequence that a significant qualitative improvement of the image quality can be achieved. This improvement is based in particular on the significant reduction of background noise and the reduced occurrence of artifacts, which are mainly caused by the abdominal wall.
- Among other things, the method is suitable to correctly classify the classic hemangioma (“hemangioma”) and the dysontogenetic (“caused by an embryonic developmental disorder”) liver cyst.
Color Doppler sonography of the liver
- Color Doppler sonography (synonym: color-coded Doppler sonography, FKDS) is an extension of conventional sonography, the use of which allows the assessment of venous or arterial blood flow and can thus contribute to the detection (determination) of circulatory disorders. However, it should be noted that both color Doppler sonography with intravenous injection of signal enhancers and when this so-called ultrasound contrast agent was not used did not provide any discernible improvement in liver diagnostics. It can be concluded that the procedure has no positive effect on the detection of circumscribed lesions.
- Nevertheless, Doppler sonography should be used as a procedure for specific issues such as space-occupying processes, since tumor can often be associated with blood flow obstruction. In addition, the procedure is a cost-effective and fast procedure.
- The difference between conventional color Doppler sonography is the detection of stimulated acoustic emissions, which can be determined with a color Doppler. The emissions represent sound pulses that vibrate as a result of stimulation of microbubbles and release energy through a change of state. The color Doppler is based on the principle of registration and conversion of these pulses, so that after coding has taken place, the sound waves can be displayed in color Doppler mode.
- To understand color sonography of the liver, it is important to know that a non-pathologically altered liver is color coded in sonography. For example, if a circumscribed lesion is present as a pathologic finding, this will be evident in color Doppler sonography by an absence of a display color.
- Depending on the method, liver imaging can also be achieved by using contrast medium (see CEUS below). However, the application of the contrast agent varies from conventional contrast imaging. The applied contrast agent is phagocytosed (uptake of substances to be eliminated) after a blood pool phase in the reticulohistiocytic system (phagocytic cell system). Due to this degradation, the contrast agent can be imaged even several days after application.
Contrast-enhanced ultrasound (“contrast-enhanced ultrasound” [CEUS]).
- Contrast-enhanced ultrasound (CEUS) is the use of ultrasound contrast medium in traditional medical sonography.
- CEUS is the only cross-sectional imaging technique that allows real-time examination of all contrast phases.
- Use in sonographic tumor diagnosis: dynamic quantitative CEUS (D-CEUS) allows quantification of liver tumor perfusion by recording the influx and efflux kinetics of the contrast agent in the different contrast phases.
- Any liver tumor is considered suspicious for malignancy that washes out on CEUS in the portal or later phases.
- The procedure is appropriate in patients with newly diagnosed solid liver tumor (with or without cirrhosis) to characterize it.
- CEUS achieves diagnostic accuracy greater than 90% in characterizing unclear liver tumors.
- A major advantage of CEUS is that the procedure can be used without hesitation in patients with intolerance or contraindications to contrast agents in computed tomography (CT) or magnetic resonance imaging (MRI).
Intraoperative ultrasonography
- Intraoperative ultrasonography is a highly accurate procedure for excluding liver metastases (stray lesions from malignant tumors).
- To improve the intraoperative assessment of pathological processes, if any, the procedure is a reliable option, especially in conjunction with laparoscopy.
- However, the disadvantage of this method is the high time required to perform the procedure, so that a significant increase in the duration of surgery is caused. Consequently, the anesthesia time must also be extended accordingly.
Assessment of the liver including normal values
| Assessment of anatomic structures incl. measurements, echogenicity, etc. | Exemplary clinical findings incl. measurements |
| Liver size |
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| Liver shape and contour |
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| Echogenicity? |
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| Homogeneity? |
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| Vessels |
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| Liver Gate |
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| Hepatic vein star, i.e., configuration of the three hepatic veins at their junction with the inferior vena cava |
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| Morrison’s pouch (spatium hepatorenale) |
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Possible complications
- No complications can be mentioned for conventional liver ultrasonography. However, allergic reactions may occur due to the use of the ultrasound contrast agent.
