Pyogenic hepatic abscesses: distinctive features from hypovascular hepatic malignancies on contrast-enhanced ultrasound with SH U 508A; early experience

Contrast-Enhanced Ultrasound (CEUS) in Non-Traumatic Abdominal Emergencies

Conventional ultrasound imaging (US) is the first-line investigation in acute non-traumatic abdominal emergencies, but sometimes it needs further examinations, such as computed tomography (CT), to reach a certain diagnosis. Contrast-enhanced ultrasound (CEUS), through injection of contrast medium, may provide the radiologist with additional information that could not be investigated with baseline US. It could help reach a diagnosis and rapidly determine the proper therapy in an emergency setting. The purpose of this review is to explain and illustrate the various possibilities and limitations of CEUS in acute non-traumatic abdominal diseases, in particular acute inflammation, parenchymal infarcts, and hemorrhages.

Contrast-Enhanced Ultrasound Appearance of Hypervirulent Klebsiella pneumoniae Liver Abscesses

There has been a paradigm shift with Klebsiella pneumoniae (KP) emerging as the most frequently isolated bacterium in pyogenic liver abscesses in immunocompetent patients. Colonization of this hypervirulent KP strain has led to community-acquired liver abscesses. Septic seeding to distant sites of the body has been recognized and is strongly associated with diabetes. Contrast-enhanced computed tomographic features have been described. Grayscale ultrasound (US) features remain inconclusive, with variable US appearances. Here we describe the contrast-enhanced US features of KP liver abscesses, which correlated with previously described computed tomographic findings. The use of contrast-enhanced US eliminates the need for radiation exposure.

Morphological and dynamic evaluation of complex cystic focal liver lesions by contrast-enhanced ultrasound: current state of the art

Complex cystic and cystic-like focal liver lesions (FLLs) encompass a spectrum of disorders ranging from non-neoplastic conditions to benign and malignant tumors. In this prospective, the possibility of non-invasive differentiation of these lesions is extremely important, because the clinical implications and therapeutic strategies vary considerably. Because of its advantageous cost/benefit ratio, widespread availability and easy execution, ultrasound (US) is the first-line imaging modality in most countries for the initial liver survey and represents the imaging technique that usually detects a complex liver cyst. However, US showed poor efficacy in the differential diagnosis of complex cystic FLLs. Thus, for years, computed tomography (CT) and magnetic resonance (MR) imaging have been used for further assessment of these lesions. Recently, the development of low mechanical index real-time contrast-enhanced ultrasound (CEUS) technique performed with the second generation of US contrast agents has led to an accurate depiction of macrovasculature and microvasculature. The technique yields information about contrast enhancement of the liver and FLLs almost as CT and MRI do, but in real time and without the use of ionizing radiation. To date, there is only a small amount of evidence about the role of CEUS in the less common setting of complex liver cysts. The aim of this review is to offer an up-to-date overview on the state of the art of CEUS in the study of the most common complex cystic focal liver lesions. To our knowledge, there are no literature comprehensive reviews on this topic.

Imaging findings of mimickers of hepatocellular carcinoma

Radiological imaging plays a crucial role in the diagnosis of hepatocellular carcinoma (HCC) as the noninvasive diagnosis of HCC in high-risk patients by typical imaging findings alone is widely adopted in major practice guidelines for HCC. While imaging techniques have markedly improved in detecting small liver lesions, they often detect incidental benign liver lesions and non-hepatocellular malignancy that can be misdiagnosed as HCC. The most common mimicker of HCC in cirrhotic liver is nontumorous arterioportal shunts that are seen as focal hypervascular liver lesions on dynamic contrast-enhanced cross-sectional imaging. Rapidly enhancing hemangiomas can be easily misdiagnosed as HCC especially on MR imaging with liver-specific contrast agent. Focal inflammatory liver lesions mimic HCC by demonstrating arterial-phase hypervascularity and subsequent washout on dynamic contrast-enhanced imaging. It is important to recognize the suggestive imaging findings for intrahepatic cholangiocarcinoma (CC) as the management of CC is largely different from that of HCC. There are other benign mimickers of HCC such as angiomyolipomas and focal nodular hyperplasia-like nodules. Recognition of their typical imaging findings can reduce false-positive HCC diagnosis.

Emergency radiology

US has a relevant role in the initial assessment of non-traumatic emergencies of the abdomen, sometimes being conclusive and some other times for selecting the patients for further imaging with CT. Injection of a contrast medium may give to the radiologist additional information to that obtained at baseline US and Doppler examination, since real-time, contrast-enhanced US (CEUS) may allow observing findings in the abdomen not recognizable at baseline US or even at color Doppler imaging. Extravascular use of microbubbles may also be useful in clinical practice to rapidly solve a number of unclear aspects. CEUS has a number of distinct advantages in acute patients, including its quickness, low invasiveness, and its possible bedside use. The information based on contrast enhancement is useful for initial diagnosis, therapeutic decision making, and follow-up of the critically ill patients. The purpose of this review is to illustrate the possibilities and limitations of abdominal CEUS in the acute setting, with special emphasis on the detection and characterization of acute inflammatory processes, infarcts, and hemorrhages.

Usefulness of contrast-enhanced ultrasound with Sonazoid for evaluating liver abscess in comparison with conventional B-mode ultrasound

AIM

The purpose of this study was to evaluate the usefulness of contrast-enhanced ultrasound (CEUS) with Sonazoid (perfluorobutane) in patients with liver abscess. Sonazoid is a contrast agent with a low mechanical index and is phagocytosed by Kupffer cells.

METHODS

Twenty-two patients with liver abscess were evaluated with conventional US, real-time CEUS with Sonazoid, and enhanced computed tomography (CT). After 0.5 mL of Sonazoid was administrated i.v., CEUS images in the vascular and post-vascular phases were observed.

RESULTS

Conventional US showed hypoechoic lesions in 13 (59.1%), isoechoic in four (18.2%), hyperechoic in two (9.1%), mixed echoic in two (9.1%) and undetected in one (4.8%) patient. CEUS showed perilesional enhancement in 19 (86.4%) lesions in the vascular phase and well-defined unenhanced areas in 22 (100%) lesions in the post-vascular phase. CEUS revealed that 18 abscesses were cystic type and three were honeycomb type. Twenty-one abscesses (95.5%) had clearer appearances on CEUS than on conventional US in regard to the extent of necrotic or liquefied lesions seen. We could confirm reduction of the lesions after therapy in 13 (92.9%) of 14 patients followed up by CEUS.

CONCLUSION

Most of the liver abscesses showed perilesional enhancement in the vascular phase and unenhanced areas in the post-vascular phase. The appearance of liver abscesses was clearer on CEUS than on conventional US. CEUS with Sonazoid can be a more effective diagnostic and therapeutic tool for liver abscess.

Spectral CT imaging in the differential diagnosis of necrotic hepatocellular carcinoma and hepatic abscess

AIM

To explore the value of CT spectral imaging in the differential diagnosis of necrotic hepatocellular carcinoma (nHCC) and hepatic abscess (HA) during the arterial phase (AP) and portal venous phase (PP).

MATERIALS AND METHODS

Sixty patients with 36 nHCCs and 24 HAs underwent spectral CT during AP and PP. Iodine or water concentration were measured and the normalized iodine concentration (NIC) and lesion-normal parenchyma iodine concentration ratio (LNR) were calculated. The two-sample t-test was used to compare quantitative parameters. Two readers qualitatively assessed lesion types according to imaging features. Sensitivity and specificity were compared between the qualitative and quantitative studies.

RESULTS

NIC and LNR in the AP for the wall of nHCC (0.14 ± 0.04 mg/ml; 2.77 ± 0.74) were higher than those of HA (0.13 ± 0.02 mg/ml; 1.4 ± 0.9). NIC and LNR in the PP for the wall of HA (0.66 ± 0.05 mg/ml; 1.2 ± 0.2) were higher than those of nHCC (0.5 ± 0.11 mg/ml; 0.94 ± 0.12). The differences in NIC in the AP were not significant but the differences in LNR in AP, and NIC and LNR in the PP were significant. The best quantitative parameter was LNR in AP, and a threshold of 1.52 would yield a sensitivity and specificity of 100% and 91.7%, respectively, for differentiating nHCC from HA.

CONCLUSION

CT spectral imaging with quantitative iodine concentration analysis may help to increase the accuracy of differentiating nHCC from HA.

Bedside contrast-enhanced sonography of critically ill patients

The transfer of critically ill patients to the radiology department is, in itself, potentially dangerous, so radiologists are frequently asked to perform bedside sonographic studies in the intensive care unit, surgical or medical department, sterile area, and operating room. In these circumstances, injection of a contrast agent may give the radiologist relevant additional information, which is useful for diagnosis and for better therapeutic management of these critically ill patients. Contrast-enhanced sonography may allow detection of findings not recognizable on baseline sonography or even color Doppler imaging. In this pictorial essay, we highlight the value of real-time contrast-enhanced sonography when performed at the bedside in critically ill patients.

Hypervascular liver masses on contrast-enhanced ultrasound: the importance of washout

OBJECTIVE

The objective of our study was to determine the role of negative enhancement (washout), its presence and timing, in the differential diagnosis of hypervascular liver masses on contrast-enhanced ultrasound.

MATERIALS AND METHODS

One-hundred forty-six hypervascular liver lesions (mean size, 3.9 cm; range, 1.0-17.0 cm) were evaluated with contrast-enhanced ultrasound over a 6-month period. Seventy-four were benign (29 hemangiomas, 31 focal nodular hyperplasia [FNH] lesions, seven adenomas, five inflammatory lesions, two other) and 72, malignant (41 hepatocellular carcinomas [HCCs], 25 metastases, six other). Two independent reviewers retrospectively recorded the presence and timing of washout in the portal venous phase, observing until 4 minutes after injection, of a contrast agent (perflutren microspheres). Diagnoses were confirmed by histopathology (n = 68) or clinicoradiologic follow-up (n = 78). Timing of washout was compared between types of lesion using Fisher's exact test.

RESULTS

Washout occurred in both benign (27/74, 36%) and malignant (70/72, 97%) lesions but was more frequently seen in malignancy (p < 0.001) (kappa = 0.91). Metastases showed more rapid washout than HCCs (p < 0.001): 20 of 25 metastases showed washout by 30 seconds after injection and 23 of 41 HCCs, later than 75 seconds. All malignant lesions without washout were HCCs (2/41). Among the benign lesions, all five inflammatory lesions showed rapid washout before 75 seconds and six of seven adenomas showed washout, mostly later than 75 seconds (5/6). Washout also occurred in hemangiomas (6/29) and FNH lesions (9/31), mostly later than 75 seconds after injection (12/15).

CONCLUSION

Hypervascular malignant lesions show washout except infrequent cases of HCC. Rapid washout characterizes metastases, whereas HCCs show variable, often slow, washout. However, washout is not unique to malignancy and may be seen in benign lesions.

Characterization of focal liver lesions with contrast-enhanced ultrasound

The introduction of second generation microbubble ultrasound (US) contrast agents, such as SonoVue (Bracco, Milan, Italy), has considerably improved the diagnostic yield of US imaging for the evaluation of focal hepatic lesions in recent years because of its ability to very sensitively depict tumoral vascularity. In addition, contrast-enhanced US (CEUS) has the advantage of the absence of ionizing radiation, the widespread availability, even at the bedside, and the possibility to characterize a lesion as soon as detected on conventional B-mode US, commonly used as the first technique for exploration of the liver. The present review focuses on the basic principles of the technique and the various patterns of benign and malignant hepatic lesions at CEUS, contributing to their characterization. Understanding of these enhancement features at CEUS according to the type of tumors enables to make more accurate characterization of focal liver lesions as well as give better advice to oncologists, hepatologists or other clinicians in case of suspected liver tumors.

Real-time contrast-enhanced ultrasound imaging of infected focal liver lesions

OBJECTIVE

The purpose of this study was to investigate the features of infected focal liver lesions on contrast-enhanced ultrasound (CEUS) imaging.

METHODS

Thirty-two hepatic abscesses, 15 infected granulomas, and 6 inflammatory pseudotumors in 53 patients were evaluated with real-time CEUS before awareness of the definitive diagnosis. A 2.4-mL dose of a sulfur hexafluoride-filled microbubble contrast agent was administered by intravenous bolus injection.

RESULTS

The numbers of abscesses with hyperenhancement, isoenhancement, and hypoenhancement in the arterial phase were 26 (81.3%), 5 (15.6%), and 1 (3.1%), respectively. Thirty (93.8%) lesions were irregularly rim enhanced with nonenhanced areas; enhanced septa were shown in 22 (68.8%) lesions; and transient hyperenhancement of liver parenchyma around the lesion was shown in 20 (62.5%). In 31 abscesses with hyperenhancement or isoenhancement in the arterial phase, 25 (80.6%) showed contrast wash-out and changed in appearance to hypoenhancement in the late phase. As for infected granulomas and inflammatory pseudotumors, 16 (76.2%) lesions showed hyperenhancement or isoenhancement in the arterial phase, and all of them were hypoenhanced in the portal and late phases.

CONCLUSIONS

Most infected focal liver lesions showed more rapid contrast wash-out than the surrounding liver parenchyma, which is similar to malignant lesions. Abscesses typically showed features of rim enhancement, enhanced internal septa, nonenhanced central necrotic areas, and transient hyperenhanced liver parenchyma around the lesions. The CEUS appearance of infected granulomas and inflammatory pseudotumors was variable, and a biopsy was necessary for definitive diagnosis.

Focal liver lesions: can SonoVue-enhanced ultrasound be used to differentiate malignant from benign lesions?

OBJECTIVE

To evaluate whether contrast-enhanced ultrasound (CEUS) with SonoVue could differentiate malignant focal liver lesions (FLLs) from benign lesions and provide lesion type diagnoses.

MATERIALS AND METHODS

Four hundred fifty-six patients with 554 FLLs were examined by CEUS with SonoVue using low mechanical index, nonlinear imaging techniques. Each lesion was characterized by 2 independent off-site readers as malignant or benign and given specific lesion type diagnosis, if possible, both at baseline ultrasound (US) and after SonoVue administration (CEUS). The final diagnosis was achieved by histopathology obtained from biopsy or surgical specimens, or by typical manifestation on contrast-enhanced CT or MRI.

RESULTS

The diagnostic accuracies of the 2 readers were 41.9% and 35.2% for baseline US, which improved significantly to 87.2% and 87.9% for CEUS (P < 0.05). Interreader agreement also increased with CEUS compared with baseline US (ê value changed from 0.49 to 0.77). The accuracy for lesion type diagnosis was 38.4% and 32.5% for baseline US, which increased to 77.6% and 78.0% for CEUS (P < 0.05).

CONCLUSIONS

CEUS with SonoVue improves differentiation between malignant and benign FLLs, and also provides improved lesion type (differential) diagnosis.

Focal liver lesions: role of contrast-enhanced ultrasound

The introduction of microbubble contrast agents and the development of contrast-specific techniques have opened new possibilities in liver imaging. Initially, only intermittent imaging with Doppler detection was available. Second-generation contrast agents and low mechanical index real-time scanning techniques are decisive advances that enable convenient liver examinations with high sensitivity and specificity. Hepatic lesions usually show typical perfusion and enhancement patterns through the various contrast phases, which help their characterization. Several published studies and the daily clinical routine show that, as opposed to conventional ultrasound (US), contrast-enhanced US can substantially improve detection and differentiation of focal liver lesions. Today, contrast-enhanced US is the dynamic imaging modality of choice for differentiation of focal liver lesions. Contrast uptake patterns of the most relevant liver lesions, as well as important clinical indications are presented and discussed.

Real-time harmonic contrast material-specific US of focal liver lesions

Recent advances in contrast material-enhanced ultrasonography (US) mainly include (a) development of low-acoustic-pressure (low-mechanical-index) harmonic software, capable of obtaining real-time images without disrupting contrast material microbubbles, and (b) commercialization of new contrast media ("second-generation" contrast media), capable of producing intense echo signals in this low-mechanical-index setting. With use of low-mechanical-index continuous-mode contrast-enhanced US, the circulatory kinetic models of various focal liver lesions can be displayed dynamically. Hepatic lesions usually have typical perfusion characteristics and enhancement patterns through the various phases of parenchymal enhancement, which helps characterize lesions and, in most cases, allows definitive diagnosis, even among lesions that exhibit very similar baseline appearances. Because of the use of harmonic technologies at low emission frequencies, there is some loss of spatial resolution and overall image quality, typically resulting in a grainy appearance. In addition, lesion depth affects the detectability of vascularity to some degree in that poor signal arises from deep-seated lesions. Moreover, liver attenuation (eg, in patients with steatosis or chronic liver disease) further reduces the sensitivity of contrast-enhanced US. Nevertheless, with its unique capacity to provide images in real time, low-mechanical-index contrast-enhanced US is the dynamic imaging modality of choice in the differential diagnosis of focal liver lesions.