Benign liver tumors in pediatric patients - Review with emphasis on imaging features

Spontaneous rupture of neonatal hepatic hemangioma diagnosed by ultrasound: A case report

Hepatic hemangioma is the most prevalent benign liver tumor during the fetal and neonatal period, and its rupture poses a severe threat to newborns' lives-this article presents a case involving the spontaneous rupture of a hepatic hemangioma in a neonate. Early diagnosis through ultrasound enabled prompt treatment, resulting in the patient's timely discharge.

Benign paediatric liver tumours: The radiological maze demystified

The trajectory from the clinical identification of a benign liver mass to establishing a precise diagnosis is perplexing and arduous. Related contributory factors are that such lesions are encountered infrequently and that there is a nonavailability of dedicated paediatric radiologists in the developing world. The objective of this study was to review the spectrum of benign liver lesions in children and their typical imaging features. Cross-sectional imaging of all paediatric patients (< 18 years) with liver lesions (single and multiple) performed in the institute from 01 January 2018 to 01 January 2019 as well as those acquired at outside institutions and referred to the institute for management was included. Ultrasound was done as the first line of investigation in all the cases with suspicious liver masses and retrospectively performed in referral cases in whom CT or MRI was already done. Images were analysed by two senior radiologists. Most of the cases were diagnosed based on clinical, biochemical and imaging findings, and biopsy was only performed in equivocal cases. Most of the benign liver lesions in the paediatric age group were hepatic haemangioma and mesenchymal hamartomas. A simplified clinical-radiologic paradigm should be established for benign liver lesions in children to assist in reaching the correct diagnosis.

Contribution

The article demonstrates the salient radiological findings of various benign liver lesions in the paediatric age group and the role of demographic, clinical and biochemical findings, which plays a substantial role in the diagnosis and avoids unnecessary biopsies.

Postnatal treatment and evolution patterns of giant fetal hepatic hemangioma: a case series of 29 patients

OBJECTIVES

To explore the clinical characteristics, postnatal treatment and prognosis of giant fetal hepatic hemangioma (GFHH).

METHOD

Retrospective analysis was performed on children with giant fetal hepatic hemangioma (maximum tumor diameter > 40 mm) diagnosed by prenatal ultrasound and MRI from December 2016 to December 2020. These patients were observed and treated at the Children's Hospital of Fudan University after birth. The clinical data were collected to analyze the clinical characteristics, treatment, and prognosis of GFHH using independent sample t tests or Fisher's exact tests.

RESULTS

Twenty-nine patients who were detected by routine ultrasound in the second and third trimester of pregnancy with giant fetal hepatic hemangiomas were included. The first prenatal ultrasound diagnosis of gestational age was 34.0 ± 4.3 weeks, ranging from 22 to 39 weeks. Of the patients, 28 had focal GFHHs and 1 had multifocal GFHHs. Surgery was performed, and the diagnosis was confirmed histopathologically in two patients. There were 8 cases with echocardiography-based evidence of pulmonary hypertension, 11 cases had a cardiothoracic ratio > 0.6, and 4 cases had hepatic arteriovenous fistula (AVF). The median follow-up time was 37 months (range: 14-70 months). During the follow-up, 12 patients received medical treatment with propranolol as the first-line therapy. The treatment group had a higher ratio of cardiothoracic ratio > 0.6 (P = 0.022) and lower albumin levels (P = 0.018). Four (14.8%) lesions showed postnatal growth before involuting. Complete response was observed in 13 (13/29) patients, and partial response was observed in 16 (16/29) patients.

CONCLUSIONS

Fetal giant hepatic hemangioma is mainly localized, and its clinical outcome conforms to RICH (rapidly involuting) and PICH (partially involuting), but some fetal giant hepatic hemangiomas will continue to grow after birth and then gradually decrease. For uncomplicated giant fetal hepatic hemangioma, postnatal follow-up is the main concern, while those with complications require aggressive medical treatment. Propranolol may have no effect on the volume change of GFHH.

Beckwith-Wiedemann syndrome with multiple hepatic and cutaneous hemangiomas in a female patient of Albanian origin: Diagnostic and therapeutic considerations

We describe a 2-month-old female infant with macroglossia, macrosomia, omphalocele, neonatal hypoglycemia, earlobe creases, low nasal bridge, midface retrusion, syndromic facies and multiple cutaneous and hepatic hemangiomas (HH). Genetic evaluation confirmed the diagnosis of Beckwith-Wiedemann Syndrome (BWS) with mosaic uniparental disomy 11 as the underlying genetic mechanism suggested by partial hypermethylation of H19/IGF2:IG-DMR and partial hypomethylation of KCNQ1OT1:TSS-DMR on chromosome 11p15.5. Pediatric endocrinology and cardiology assessments were normal. No malignant liver or renal tumors were detected during the follow-up period. Treatment with propranolol was started for the multiple HH, according to international recommendations. At 3-, 6-, and 9-month follow up, a gradual decrease in the size of the hemangiomas and AFP levels was observed, without side effects. This is the fifth case in the literature combining HH and BWS, and among these, the third case with this specific genetic defect suggesting a possible association between HH and BWS caused by 11 paternal uniparental disomy [upd(11)pat]. The case also highlights that if treatment is warranted, then oral propranolol can be used for the management of infantile HH in BWS patients similarly to non-BWS patients.

Use of CEUS for Imaging Evaluation of Pediatric Peritonsillar Abscess

PURPOSE

Peritonsillar abscess can be diagnosed by B-mode ultrasound and cross-sectional imaging. The latter (with MRI being the modality of first choice in children) is associated with higher effort and risk for pediatric patients due to the administration of X-rays and/or the need of sedation. The purpose of this study is to evaluate whether the introduction of CEUS into the diagnostic algorithm for suspected pediatric peritonsillar abscess is suitable and advantageous.

MATERIALS AND METHODS

Single-institution retrospective review of data of pediatric patients who were presented to the department of pediatric radiology for sonographic evaluation under the suspicion of peritonsillar abscess. Diagnostic performance of CEUS was evaluated by using surgical exploration or clinical follow-up as the reference standard.

RESULTS

284 children included in the study underwent B-mode ultrasound. Mean age of all patients was 6,23 years. Peritonsillar abscess was the diagnosis in 42 patients. Diagnosis of peritonsillar abscess was made by B-mode ultrasound alone in 13 of 42 patients (31 %). In 17 of 42 patients (40 %), diagnosis was made by a combination of B-mode ultrasound and CEUS. Sensitivity rose from 37 % to 86 % in cases where B-mode ultrasound remained unclear and CEUS was used.

CONCLUSION

Contrast-enhanced ultrasound (CEUS) is suitable and efficient for the diagnosis of peritonsillar abscess in pediatric patients. It increases the sensitivity for the diagnosis of peritonsillar abscess and thereby reduces the need of additional cross-sectional imaging for the pediatric patients.

Review on Pediatric Malignant Focal Liver Lesions with Imaging Evaluation: Part I

Malignant focal liver lesions (FLLs) are commonly reported in adults but rarely seen in the pediatric population. Due to the rarity, the understanding of these diseases is still very limited. In children, most malignant FLLs are congenital. It is very important to choose appropriate imaging examination concerning various factors. This paper will outline common pediatric malignant FLLs, including hepatoblastoma, hepatocellular carcinoma, and cholangiocarcinoma and discuss them against the background of the latest knowledge on comparable/similar tumors in adults. Medical imaging features are of vital importance for the non-invasive diagnosis and follow-up of treatment of FLLs in pediatric patients. The use of CEUS in pediatric patients for characterizing those FLLs that remain indeterminate on conventional B mode ultrasounds may be an effective option in the future and has great potential to be integrated into imaging algorithms without the risk of exposure to ionizing radiation.

Value of contrast-enhanced ultrasound for vascular diseases of the liver - current indications and open questions

Contrast-enhanced ultrasonography (CEUS) is a widely available and well-tolerated technique that can expand the diagnosis of a variety of vascular liver diseases. This paper presents an overview of the current possibilities of the use of CEUS in vascular liver diseases. Particularly where Doppler sonography has technical limitations, CEUS provides additional opportunities to visualize vascular thrombosis and other obstructions restricting blood flow. When CT or MRI contrast agents cannot be used because of severe allergy or renal insufficiency, CEUS can be a valuable diagnostic alternative and has demonstrated comparable diagnostic performance in at least some vascular liver diseases, such as portal vein thrombosis. In addition, CEUS works without radiation and, therefore, might be particularly suitable for young patients and children. This may be useful, for example, in congenital disorders such as persistent umbilical vein or preduodenal portal vein. Vascular liver disease is rare and comprehensive data are still lacking, but the available literature provides promising insights into potential new ways to study vascular liver disease. Although most studies are based on small sample sizes or even case reports, the high diagnostic utility is undisputed.

Pediatric Hepatocellular Adenomas: What Is Known and What Is New?

Current understanding and classification of pediatric hepatocellular adenomas (HCA) are largely based on adult data. HCAs are rare in children and, unlike in adults, are often seen in the context of syndromes or abnormal background liver. Attempts to apply the adult classification to pediatric tumors have led to several "unclassifiable" lesions. Although typically considered benign, few can show atypical features and those with beta-catenin mutations have a risk for malignant transformation. Small lesions can be monitored while larger (>5.0 cm) lesions are excised due to symptoms or risk of bleeding/rupture, etc. Management depends on gender, age, underlying liver disease, multifocality, size of lesion, histologic subtype and presence of mutation, if any. In this review, we summarize the data on pediatric HCAs and highlight our experience with their diagnosis and management.

Pedunculated Focal Nodular Hyperplasia: When in Doubt, Should We Cut It Out?

Focal nodular hyperplasia (FNH) is the second most common benign hepatic tumor and can rarely present as an exophytic solitary mass attached to the liver by a stalk. Most FNH cases are usually detected as incidental findings during surgery, imaging or physical examination and have a high female predominance. However, the pedunculated forms of FNH are particularly rare and commonly associated with severe complications and diagnostic challenges. Hence, our study aims to provide a comprehensive summary of the available data on the pedunculated FNH cases among adults and children. Furthermore, we will highlight the role of different therapeutic options in treating this clinical entity. The use of imaging techniques is considered a significant addition to the diagnostic toolbox. Regarding the optimal treatment strategy, the main indications for surgery were the presence of symptoms, diagnostic uncertainty and increased risk of complications, based on the current literature. Herein, we also propose a management algorithm for patients with suspected FNH lesions. Therefore, a high index of suspicion and awareness of this pathology and its life-threatening complications, as an uncommon etiology of acute abdomen, is of utmost importance in order to achieve better clinical outcomes.

Focal Nodular Hyperplasia in the Pediatric Population: A Multicenter Experience

BACKGROUND

Focal nodular hyperplasia (FNH) is a benign liver lesion classically presenting in young females. In children, FNH is rare and its detailed clinicopathologic characteristics remain largely unknown. Furthermore, there are no studies comparing pediatric FNH features to those presenting in adults.

METHODS

In this study, we analyzed a total of 47 FNH cases in pediatric patients (age range: 23 days to 18 years) from 3 centers and compared them to a cohort of 31 FNH cases in adult patients (age range: 20-64 years).

RESULTS

Of the pediatric cases, 13 cases (28%) had a history of a prior malignancy of which 4 were treated with chemoradiation and stem cell transplantation (SCT), 5 with chemoradiation alone and 3 with chemotherapy and SCT. In the pediatric cases 41 (87%) had a central scar and 46 (98%) had fibrous septa. Both pediatric and adult FNH were more common in female patients. Cases in pediatric patients were also significantly associated with larger size (P = .047), absence of dystrophic vessels (P = .001), absence of sinusoidal dilatation (P = .029), pseudoacini formation (P = .013), and steatosis (P = .029).

CONCLUSION

In our experience although most cases of pediatric FNH show the classic histologic features seen in adults, some significant differences exist, and awareness of these findings could aid in the evaluation of these rare cases.

The diagnostic value of Doppler Resistive Index in the differential diagnosis of focal liver lesions

Aim

To investigate the diagnostic value of resistance index (RI) in differentiating focal liver lesions.

Patients and methods

In this retrospective study, a total of 576 patients with histologically confirmed focal liver lesions were included. Each patient underwent B-mode ultrasound examination and color Doppler ultrasound examination. The RI values of different focal liver lesions were recorded and compared.

Results

The mean RI value of benign lesions was significantly lower than that of malignant lesions (0.54 ± 0.10 vs. 0.71 ± 0.12) (p <0.05). In malignant lesions, the RI value of intrahepatic cholangiocarcinoma was significantly lower than that of hepatocellular carcinoma lesions. Furthermore, in hepatocellular carcinoma lesions, the RI of large lesions (group 4: >10 cm) was significantly lower than that of small lesions (group 1: ≤2 cm, group 2: 2-5 cm) (p <0.05). Taken RI of 0.615 as a cutoff value to differentiate malignant and benign lesions, the sensitivity, specificity, positive predictive value and negative predictive value were 82.80%, 81.00%, 81.34% and 82.48%, respectively.

Conclusion

Color Doppler ultrasound examination is a valuable imaging method in detecting blood flow signal within liver lesions. The RI parameter should be helpful in differentiating malignant and benign liver tumors.

Incidental Findings in Pediatric Patients: How to Manage Liver Incidentaloma in Pediatric Patients

The World Federation for Ultrasound in Medicine and Biology (WFUMB) is addressing the issue of incidental findings (IFs) with a series of publications entitled "Incidental imaging findings-the role of ultrasound". IFs in the liver of newborns and children are rare and much less commonly encountered than in adults; as a result, they are relatively much more frequently malignant and life-threatening, even when they are of benign histology. Conventional B-mode ultrasound is the well-established first line imaging modality for the assessment of liver pathology in pediatric patients. US technological advances, resulting in image quality improvement, contrast-enhanced ultrasound (CEUS), liver elastography and quantification tools for steatosis have expanded the use of ultrasound technology in daily practice. The following overview is intended to illustrate incidentally detected liver pathology covering all pediatric ages. It aims to aid the examiner in establishing the final diagnosis. Management of incidentally detected focal liver lesions (FLL) needs to take into account the diagnostic accuracy of each imaging modality, the patient's safety issues (including ionizing radiation and nephrotoxic contrast agents), the delay in diagnosis, the psychological burden on the patient and the cost for the healthcare system. Moreover, this paper should help the pediatric clinician and ultrasound practitioner to decide which pathologies need no further investigation, which ones require interval imaging and which cases require further and immediate diagnostic procedures.

Imaging strategy for focal nodular hyperplasia in children: long-term experience from two specialist European centres

BACKGROUND

Focal nodular hyperplasia (FNH) in children is a rare but benign tumour, which must be differentiated from malignant entities to avoid unnecessary treatment, leading to potential morbidity.

OBJECTIVES

To provide data on imaging findings of these lesions with a suggested algorithm for diagnosis, sampling and follow-up.

MATERIALS AND METHODS

This retrospective review evaluated imaging of all patients diagnosed with FNH in two tertiary referral centres in Europe between 1975 and 2018.

RESULTS

One hundred and four patients with 137 tumours were reviewed. The mean age at presentation was 8.2 years. The median tumour size was 5 cm (range: 0.3-29 cm). Multiple lesions were seen in 16.3% of patients. The male-to-female ratio was 1:2.

CONCLUSION

FNH with typical features on imaging can be safely followed up once the diagnosis has been established. The use of contrast-enhanced ultrasound and magnetic resonance imaging allows accurate characterisation in most cases. Histological sampling is only advised when there is diagnostic doubt. Atypical arterial enhancement of FNH should prompt the search for a congenital portosystemic shunt.

Case Report: Rare Acute Abdomen: Focal Nodular Hyperplasia With Spontaneous Rupture

Focal nodular hyperplasia (FNH) of the liver is a benign lesion characterized by hypertrophic nodules with central star-shaped fibrous scars. The etiology and pathogenesis of FNH are not completely understood. A 43-year-old man was hospitalized because of acute abdominal pain. Emergency computed tomography(CT) showed hepatic tumor rupture and bleeding. The patient’s condition improved following arteriographic embolization to stop bleeding. Laparotomy confirmed spontaneous rupture and hemorrhage of focal hyperplasia and the patient remains asymptomatic after an uneventful recovery. FNH with spontaneous rupture and bleeding is extremely rare. Currently, there is no unified management standard for FNH and most previous studies recommend observation and follow-up. We recommend consideration of surgical treatment of cases with spontaneous rupture and bleeding.

Incidental Liver Lesions in children: A practical and evidence-based approach

Incidental liver lesions are increasingly being discovered in the context of the increased use of ultrasound studies and the majority are benign. In children, although individually rare, the differential diagnosis is broad and therefore a systematic approach is of utmost importance to reduce the radiological and disease burden in children and their families. This review article collected current evidence and provides fundamental information for the clinician regarding specific differential diagnoses and unique imaging features of benign liver lesions in children. Ultimately, we propose a practical stepwise approach mainly involving clinical and radiological workup. Laboratory tests and histopathological examination may be necessary in the presence of red flags or in indeterminate lesions.

[Budd-Chiari syndrome, review and illustration]

Budd-Chiari syndrome is a rare vascular disorder characterized by obstruction of the hepatic venous outflow. Various diseases causing coagulopathy play a role in aetiology, such as myeloproliferative disorders. Acute vascular occlusion may lead to acute phlebitis with fever. The classic triad of acute liver failure may be present with ascites, hepatomegaly, and abdominal pain. However, subacute courses of disease were also observed. Because of the variable symptoms and severity extent, depending on the acuity of the course and the extent of the affected vessels, diagnosis is often difficult. Sonography, as a ubiquitously available and cost-effective diagnostic tool, plays a leading role. Doppler ultrasonography can be used to visualize hemodynamics in particular. In acute thrombotic occlusion, the affected hepatic veins usually cannot or only partially be visualized. In non-occluding thrombi, turbulent flow patterns may develop in the area of venous outflow obstruction, and flow velocity is then increased in the area of stenosis. Contrast enhanced ultrasound offers even better specificity of diagnosis. Computed tomography and magnetic resonance imaging can directly visualize thrombi and the cause of obstruction. Once the diagnosis is confirmed, anticoagulation must be initiated, but therapy of the underlying disease must also be started. If symptom-controlling measures are not sufficient, angioplasty/stenting to reopen short-segment stenoses or implantation of a TIPSS device may be considered. Liver transplantation remains ultima ratio. As studies on the precision of diagnostic methods are controversial, the characteristics of imaging for BCS are therefore summarized in this review on the basis of several illustrating case reports.

Liver tumors in children with chronic liver diseases

Liver tumors are rare in children, but the incidence may increase in some circumstances and particularly in chronic liver diseases. Most liver tumors consequent to chronic liver diseases are malignant hepatocellular carcinoma. Other liver tumors include hepatoblastoma, focal nodular hyperplasia, adenoma, pseudotumor, and nodular regenerative hyperplasia. Screening of suspected cases is beneficial. Imaging and surrogate markers of alpha-fetoprotein are used initially as noninvasive tools for surveillance. However, liver biopsy for histopathology evaluation might be necessary for patients with inconclusive findings. Once the malignant liver tumor is detected in children with cirrhosis, liver transplantation is currently considered the preferred option and achieves favorable outcomes. Based on the current evidence, this review focuses on liver tumors with underlying chronic liver disease, their epidemiology, pathogenesis, early recognition, and effective management.

Contrast-Enhanced Ultrasound as a Main Radiological Diagnostic Method for Primary Liver Neoplasms and Hemangiomas

Contrast-enhanced ultrasound (CEUS) is a relatively new approach for the definitive diagnosis of focal liver lesions (FLL). The essential advantages of CEUS are affordability, absence of radiation, and negligible nephrotoxicity-making this diagnostic approach more preferable.

This review includes data from 39 different research studies published during the last 10 years, selected through the MeSH strategy in PubMed.

We conclude that CEUS is a promising approach for diagnosing primary liver neoplasms and it is an excellent radiological approach for children and pregnant women because of the absence of radiation and nephrotoxicity. Studies showed that CEUS is a very good approach for the differentiation of a variety of hemangiomas and for a detailed description of those findings. Therefore, CEUS is an important and progressive method for the diagnosis of liver neoplasms. The regular use of CEUS will facilitate the diagnosis of primary liver lesions.

Use of contrast-enhanced ultrasound in pediatrics

Although contrast-enhanced ultrasound has been shown to provide considerable benefits, particularly in pediatric patients, it is still used relatively rarely in Brazil. It has proven to be a safe technique, and adverse effects are rare. In this review, we address the technique and main applications of contrast-enhanced ultrasound in the pediatric population, including the evaluation of focal liver lesions, abdominal trauma, kidney grafts, liver grafts, bowel loops, and vesicoureteral reflux. It is important for pediatric radiologists to be acquainted with this promising tool, understanding its applications and limitations.

Fine needle aspiration cytology of mesenchymal hamartoma of liver mimicking hepatoblastoma: A case report

Fine-needle aspiration cytology (FNAC) is an effective tool for early and quick diagnosis of malignant and metastatic liver masses. However, diagnosing a benign liver tumor on cytology is a challenging task as they are rarely assessed on cytology and also due to the limitations of the procedure. Mesenchymal hamartoma is an uncommon benign pediatric liver tumor and difficult to diagnose on cytology. We describe here a case of a child who presented with a huge liver mass and clinical suspicion of hepatoblastoma. The child underwent blind FNA, and was diagnosed as mesenchymal hamartoma based on the cytological features. A biopsy was performed subsequently which confirmed the same and then he underwent surgical resection of the tumor. The patient had an uneventful recovery and is disease free on follow up.

[Imaging of hepatic tumors in children and adolescents]

BACKGROUND

Pediatric liver tumors are relatively rare, but thorough knowledge of their imaging features is still important.

OBJECTIVES

Frequency and imaging features of benign and malignant liver masses during childhood and adolescence.

MATERIALS AND METHODS

Discussion of relevant original articles, review manuscripts and expert recommendations concerning imaging of childhood liver tumors.

RESULTS

The most common malignant tumors of the liver are hepatoblastoma, which usually occur in younger children, as well as in some regions hepatocellular carcinoma. In contrast to most benign masses, such as focal nodular hyperplasia, simple cysts or fatty liver infiltrations, their imaging morphology is not very characteristic. Radiologically, sonography and magnetic resonance imaging (MRI) are used for assessment. Both methods benefit from intravenous contrast agent administration.

CONCLUSIONS

Childhood liver tumors show a broad spectrum of morphological manifestations. Some entities can be characterized using standard imaging, some require multimodal imaging or histological assessment. In addition to morphological imaging criteria, age and the medical history as well as laboratory data play an important role in establishing the correct diagnosis.

Pediatric fibrolamellar hepatocellular carcinoma: case report and review of the literature

BACKGROUND

A 13-year-old boy presented with acute abdominal pain in the right upper quadrant without previous trauma. Abdominal ultrasound (US) revealed a mass in the right liver lobe with free intraperitoneal fluid, suggestive for hemoperitoneum. Magnetic resonance imaging confirmed a subcapsular lesion (5.7 × 4.6 × 4.1 cm), suggestive for fibrolamellar hepatocellular carcinoma (FL-HCC). Positron emission tomography-computed tomography revealed mild to moderate fluorodeoxyglucose (FDG) avidity, with no other FDG avid lesions. Hepatic tumor markers were negative.

CASE REPORT

An elective right hepatectomy with cholecystectomy and hilar lymph node resection was performed.

RESULTS

Histology showed a central fibrous scar and confirmed a FL-HCC (pT1bN0M0). The resected lymph nodes were tumor-free. Treatment of FL-HCC should consist of complete tumor resection with concurrent lymph node resection +/- orthotopic liver transplantation. Long-term follow-up is advised. A follow-up interval of 3-4 months in the first 2 years after surgical resection can be justified as FL-HCC have a high recurrence rate of more than 50% within 10-33 months.

CONCLUSIONS

Malignancy can be a rare cause of abdominal pain in pediatric patients. An abdominal US is essential to prevent misdiagnosis. Treatment of FL-HCC should consist of R0 tumor resection with concurrent lymphadenectomy +/- orthotopic liver transplantation.

Imaging Features of Fibrolamellar Hepatocellular Carcinoma with Contrast-Enhanced Ultrasound

PURPOSE

 Fibrolamellar hepatocellular carcinoma (f-HCC) is a rare primary liver tumor. Imaging plays an important role in diagnosis. The aim of this retrospective study was to analyze contrast-enhanced ultrasound (CEUS) features of histologically proven f-HCC in comparison to benign focal nodular hyperplasia (FNH).

MATERIALS & METHODS

 16 patients with histologically proven f-HCC lesions and 30 patients with FNH lesions were retrospectively reviewed regarding CEUS features to determine the malignant or benign nature of the focal liver lesions (FLL). Five radiologists assessed the CEUS enhancement pattern and came to a consensus using the EFSUMB (European Federation of Societies for Ultrasound in Medicine and Biology) guideline criteria.

RESULTS

 Fibrolamellar hepatocellular carcinoma manifested as a single and huge FLL. On CEUS, f-HCC showed heterogeneous hyperenhancement in the arterial phase and hypoenhancement (16/16, 100 %) in the portal venous and late phases (PVLP) as a sign of malignancy. In contrast to the hypoenhancement of f-HCC in the PVLP, all patients with FNH showed hyperenhancement as the most distinctive feature (P < 0.01). 8 f-HCC lesions showed a central scar as an unenhanced area (8/16, 50.0 %), which could also be detected in 53.3 % (16/30) of FNH lesions (P > 0.05).

CONCLUSION

 By analyzing the hypoenhancement in the PVLP, CEUS imaging reliably diagnosed f-HCC as a malignant FLL. CEUS also showed differentiation between f-HCC and FNH lesions, showing similar non-enhanced central scars, whereas f-HCC lesions showed peripheral hyperenhancement in the arterial phase and early washout in the PVLP.

Infantile hepatic haemangioendothelioma resection in a newborn: A case report and literature review

Infantile hepatic haemangioendothelioma (IHH) is the most common benign hepatic tumour in infants. However, experience of managing IHH is lacking and treatments for symptomatic IHH are controversial. Here we report the case of a patient with IHH treated by liver resection. A liver mass was found in a newborn by prenatal ultrasonography. The patient presented with abdominal distention with a tangible mass. Further imaging diagnosis and biopsy were carried out and complete surgical resection of the mass was performed. Histological examination confirmed IHH. The patient recovered uneventfully after surgery, with no additional therapy after discharge and no recurrence during follow-up. We also summarise previously published resected cases of IHH and review the surgical outcomes. Surgical resection and liver transplantation appear to be effective treatments for symptomatic IHH.

A case of idiopathic portal hypertension accompanying multiple hepatic nodular regenerative hyperplasia in a patient with systemic sclerosis

Idiopathic portal hypertension (IPH) is one of the background diseases causing nodular regenerative hyperplasia (NRH). Furthermore, IPH patients accompanied with autoimmune diseases, such as systemic lupus erythematosus (SLE) and systemic sclerosis (SSc), are more likely to form NRH in the liver. A 76-year-old woman had been aware of the Raynaud's phenomenon and scleroderma for the past 30 years. In this case, she presented with abdominal fullness, and her imaging analysis revealed ascites and multiple liver nodules. On Gd-EOB-DTPA enhanced magnetic resonance imaging (EOB-MRI), donut-like uptake was observed in the nodules in the hepatobiliary phase. Liver biopsy of a nodule demonstrated that it was composed of hyperplastic hepatocytes without fibrous septa, and dilated sinusoids were observed beside the nodule. Conversely, background liver showed that peripheral portal veins appeared stenotic with dense fibrosis in the portal area. The final diagnosis was that multiple NRH of the liver developed in SSc patient accompanying IPH. This case suggests that NRH may be unexpectedly diagnosed in patients with autoimmune diseases accompanying IPH.

Paediatric gastrointestinal and hepatobiliary radiology: why do we need subspecialists, and what is new?

We present the case for subspecialisation in paediatric gastrointestinal and hepato-pancreatico-biliary radiology. We frame the discussion around a number of questions: What is different about the paediatric patient and paediatric gastrointestinal system? What does the radiologist need to do differently? And finally, what can be translated from these subspecialty areas into everyday practice? We cover conditions that the sub-specialist might encounter, focusing on entities such as inflammatory bowel disease and hepatic vascular anomalies. We also highlight novel imaging techniques that are a focus of research in the subspecialties, including contrast-enhanced ultrasound, MRI motility, magnetisation transfer factor, and magnetic resonance elastography.

Liver Tumors in Pediatric Patients

The most recent advance in the care of children diagnosed with hepatoblastoma and hepatocellular carcinoma is the Pediatric Hepatic International Tumor Trial, which opened to international enrollment in 2018. It is being conducted as a collaborative effort by the pediatric multicenter trial groups in North America, Europe, and the Far East. This international effort was catalyzed by a new unified global risk stratification system for hepatoblastoma, an international histopathologic consensus classification for pediatric liver tumors, and a revised 2017 collaborative update of the PRE-Treatment EXTent of disease radiographic based staging system.

Focal nodular hyperplasia in a 14-year-old child: A case report

BACKGROUND

Focal nodular hyperplasia (FNH) is a benign rare liver neoplasm in children and includes only 2% of all pediatric liver tumors. Here we reported the case of a 14-year-old girl with vague flank pain who was managed conservatively.

CASE PRESENTATION

Our case is a 14-year-old child (female), with a 5 cm diameter lesion in the right lobe of the liver in CT scan, and histologic findings compatible with FNH. A solid mass lobulated contour, intense enhancement with a hypodense central area, possibly indicative of central scar, was seen. Despite her mild flank pain we did not insist on surgical resection and managed her conservatively. Her pain resolved 2 weeks later and an imaging follow-up with ultrasound 6 months later showed no increase in size or numbers.

CONCLUSION

FNH is an uncommon mass lesion in children. Our patient had mild symptomatic severity, and several guidelines recommend surgical treatment in this condition, but our team performed conservative and medical treatment for her and got the desired result. Therefore, the combination of these factors raises the importance of introducing the case. According to FNH's nature, stability, complications, and evaluation of pain are essential to avoid unnecessary surgeries.

Contrast-enhanced ultrasound of benign and malignant liver lesions in children

Contrast-enhanced ultrasound (CEUS) is increasingly being used in children. One of the most common referrals for CEUS performance is characterization of indeterminate focal liver lesions and follow-up of known liver lesions. In this setting, CEUS is performed with intravenous administration of ultrasound contrast agents (UCAs). When injected into a vein, UCA microbubbles remain confined within the vascular network until they dissipate. Therefore, visualization of UCA within the tissues and lesions corresponds to true blood flow. CEUS enables continuous, real-time observation of the enhancement pattern of a focal liver lesion, allowing in most cases for a definite diagnosis and obviating the need for further cross-sectional imaging or other interventional procedures. The recent approval of Lumason (Bracco Diagnostics, Monroe Township, NJ) for pediatric liver CEUS applications has spurred the widespread use of CEUS. In this review article we describe the role of CEUS in pediatric liver applications, focusing on the examination technique and interpretation of main imaging findings of the most commonly encountered benign and malignant focal liver lesions. We also compare the diagnostic performance of CEUS with other imaging modalities for accurate characterization of focal liver lesions.

An Unusual Case of Neonatal High-Output Heart Failure: Infantile Hepatic Hemangioma

BACKGROUND

Infantile hepatic hemangioma (IHH) is a rare but life-threatening disorder that must be considered in the newborn presenting with high-output heart failure (HF). IHH is a tumor comprised of large vascular beds, which require a significant increase in blood flow as the lesion grows. This, in turn, creates an undue burden on the cardiovascular system, leading to high-output HF and potentially, respiratory distress. Recent changes have been made in the classification of certain hepatic hemangiomas and their treatments.

CASE REPORT

A 10-day-old girl presented to the Emergency Department with increased respiratory effort and an episode of apnea and cyanosis. A chest x-ray study was obtained and showed cardiomegaly and pulmonary edema concerning for HF. The patient was promptly admitted to the pediatric intensive care unit, where advanced imaging was obtained revealing findings consistent with IHH. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: HF in an infant is a critical condition often requiring prompt intervention and rapid diagnosis of the correct etiology to save a life. IHH is an example of an extrathoracic etiology of pediatric HF that has undergone recent changes in terminology and diagnosis. Increased awareness among emergency physicians of this disease process and its treatments can lead to expeditious diagnosis and treatment of this potentially life-threatening illness.

Guidelines and Good Clinical Practice Recommendations for Contrast Enhanced Ultrasound (CEUS) in the Liver - Update 2020 - WFUMB in Cooperation with EFSUMB, AFSUMB, AIUM, and FLAUS

The present, updated document describes the fourth iteration of recommendations for the hepatic use of contrast enhanced ultrasound (CEUS), first initiated in 2004 by the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB). The previous updated editions of the guidelines reflected changes in the available contrast agents and updated the guidelines not only for hepatic but also for non-hepatic applications.The 2012 guideline requires updating as previously the differences of the contrast agents were not precisely described and the differences in contrast phases as well as handling were not clearly indicated. In addition, more evidence has been published for all contrast agents. The update also reflects the most recent developments in contrast agents, including the United States Food and Drug Administration (FDA) approval as well as the extensive Asian experience, to produce a truly international perspective.These guidelines and recommendations provide general advice on the use of ultrasound contrast agents (UCA) and are intended to create standard protocols for the use and administration of UCA in liver applications on an international basis to improve the management of patients.

Guidelines and Good Clinical Practice Recommendations for Contrast-Enhanced Ultrasound (CEUS) in the Liver-Update 2020 WFUMB in Cooperation with EFSUMB, AFSUMB, AIUM, and FLAUS

The present, updated document describes the fourth iteration of recommendations for the hepatic use of contrast-enhanced ultrasound, first initiated in 2004 by the European Federation of Societies for Ultrasound in Medicine and Biology. The previous updated editions of the guidelines reflected changes in the available contrast agents and updated the guidelines not only for hepatic but also for non-hepatic applications. The 2012 guideline requires updating as, previously, the differences in the contrast agents were not precisely described and the differences in contrast phases as well as handling were not clearly indicated. In addition, more evidence has been published for all contrast agents. The update also reflects the most recent developments in contrast agents, including U.S. Food and Drug Administration approval and the extensive Asian experience, to produce a truly international perspective. These guidelines and recommendations provide general advice on the use of ultrasound contrast agents (UCAs) and are intended to create standard protocols for the use and administration of UCAs in liver applications on an international basis to improve the management of patients.

Management of focal nodular hyperplasia of the liver: Experience of 50 pediatric patients in a tertiary center

BACKGROUND

Focal nodular hyperplasia (FNH) is a rare benign hepatic lesion in children. No management guidelines for pediatric population exist because of limited evidence.

OBJECTIVE

To review the experience of a large tertiary liver center, providing additional clinical data to help formulate management guidelines for FNH in the pediatric population.

METHODS

We analyzed data of children <18 years diagnosed with FNH from 1996 to 2018 at our hospital, detailing management and long-term clinical outcome.

RESULTS

50 patients were identified. The median age was 10 years old (range 0.75-15.5 years old). The mean diameter of FNH was 5.9 cm (±3.1 cm). 10 patients had multiple lesions. First-line management: watchful waiting with serial checks (n = 37), surgery (n = 13). Of the watchful waiting patients, 10 required eventual second-line surgery. After a median follow-up of 4.7 years (range 0.5-20 years), 46 patients were asymptomatic, with no significant difference in clinical outcome (p = 0.962) between the two first-line management approaches. Lesions demonstrated growth in 13 cases: 5 of these required second-line surgery. In these patients, there was no significant difference in clinical outcome (p = 0.188) compared to nonoperative patients. Considering all surgically treated patients, there was no significant difference between first-line and second-line surgery for clinical outcome (p = 0.846), hospital stay (p = 0.410), complications (p = 0.510) and severe complications (p = 0.385).

CONCLUSIONS

Our data support the hypothesis that watchful waiting is a safe initial approach to pediatric FNH management in patients with no major symptoms or complications. Surgery should be reserved for patients with diagnostic doubt, persistent symptoms and/or biological or significant anatomical abnormalities. FNH growth alone should not be considered as an indication for surgery.

TYPE OF STUDY

Therapeutic study.

LEVEL OF EVIDENCE

Level III.

Contrast-Enhanced Ultrasound for the Characterization of Infantile Hepatic Hemangioma in Premature Neonate

Contrast-enhanced ultrasonography (CEUS) is a relatively new imaging method for use in children. It is recognized as a safe and easily performed problem-solving method.

A premature 10-day-old female infant experienced unusual persistent anemia. The diagnostic workup for the anemia included an abdominal ultrasound examination, which showed pathological formation in the left middle quadrant. MRI was used to further asses the lesion and showed a hypervascular lesion with necrotic areas rising from the left hepatic lobe, mainly showing the pattern that indicates an infantile hepatic hemangioma. Main differential diagnosis, hepatoblastoma, could not be excluded. The crucial examination used to differentiate was CEUS.

Management of benign liver tumors

Benign liver tumors in children are far less frequent than their malignant counterparts. Recently, there have been advances of diagnostic procedures and novel treatments with improved classification as a result. While malignant pediatric liver tumors have been comprehensively addressed by multicenter international tumor trials, benign tumors have more usually relied upon individualised workup and treatment. Due to the rarity and heterogeneity of these different entities, large studies are lacking. In this article the authors highlight the spectrum of benign liver tumors with special focus on specific clinical features, pathology, and treatment.

Quantitative Imaging in Pediatric Hepatobiliary Disease

Pediatric hepatobiliary imaging is important for evaluation of not only congenital or structural disease but also metabolic or diffuse parenchymal disease and tumors. A variety of ultrasonography and magnetic resonance imaging (MRI) techniques can be used for these assessments. In ultrasonography, conventional ultrasound imaging as well as vascular imaging, elastography, and contrast-enhanced ultrasonography can be used, while in MRI, fat quantification, T2/T2^* mapping, diffusion-weighted imaging, magnetic resonance elastography, and dynamic contrast-enhanced MRI can be performed. These techniques may be helpful for evaluation of biliary atresia, hepatic fibrosis, nonalcoholic fatty liver disease, sinusoidal obstruction syndrome, and hepatic masses in children. In this review, we discuss each tool in the context of management of hepatobiliary disease in children, and cover various imaging techniques in the context of the relevant physics and their clinical applications for patient care.

Diffuse infantile hepatic hemangiomas in a patient with Beckwith-Wiedemann syndrome: A new association?

Beckwith-Wiedemann syndrome (BWS) is an overgrowth syndrome, caused by alterations in a cluster of imprinted genes located within the chromosome region 11p15.5. Common clinical features are overgrowth, macroglossia, lateralized overgrowth, abdominal wall defects, neonatal hypoglycemia and an increased risk of embryonal tumors, such as hepatoblastomas. Periodic screening for abdominal tumors is recommended. Vascular tumors are uncommon in BWS. Diffuse infantile hepatic hemangiomas (DIHHs) are rare vascular tumors with potentially lethal complications, in particular acquired consumptive hypothyroidism, high-output cardiac failure, liver failure and abdominal compartment syndrome. We describe a 2-month-old patient with hallmark clinical features of BWS and confirmed a genetic diagnosis with mosaic paternal uniparental disomy of chromosome 11p15.5 (UPD[11]pat). The patient developed hepatomegaly and elevated alpha-fetoprotein (AFP) and was therefore suspected of having a hepatoblastoma. Abdominal echo-color Doppler and a CT-scan allowed diagnosis of DIHHs. She was closely monitored and underwent treatment with propranolol. Oral propranolol was effective in reducing hepatic lesions without side effects. This report may suggest that vascular tumors can also be associated with BWS.

Hepatocellular adenoma in the paediatric population: Molecular classification and clinical associations

Hepatocellular adenomas (HCAs) represent rare, benign liver tumours occurring predominantly in females taking oral contraceptives. In children, HCAs comprise less than 5% of hepatic tumours and demonstrate association with various conditions. The contemporary classification of HCAs, based on their distinctive genotypes and clinical phenotypes, includes hepatocyte nuclear factor 1 homeobox alpha-inactivated HCAs, beta-catenin-mutated HCAs, inflammatory HCAs, combined beta-catenin-mutated and inflammatory HCAs, sonic hedgehog-activated HCAs, and unclassified HCAs. In children, there is a lack of literature on the characteristics and distribution of HCA subtypes. In this review, we summarized different HCA subtypes and the clinicopathologic spectrum of HCAs in the paediatric population.

LI-RADS ancillary features on contrast-enhanced ultrasonography

The Liver Imaging Reporting and Data System (LI-RADS) was created to standardize liver imaging in patients at high risk for hepatocellular carcinoma (HCC), and it uses a diagnostic algorithm to assign categories that reflect the relative probability of HCC, non-HCC malignancies, or benign focal liver lesions. In addition to major imaging features, ancillary features (AFs) are used by radiologists to refine the categorization of liver nodules. In the present document, we discuss and explain the application of AFs currently defined within the LI-RADS guidelines. We also explore possible additional AFs visible on contrast-enhanced ultrasonography (CEUS). Finally, we summarize the management of CEUS LI-RADS features, including the role of current and potential future AFs.

MicroRNA dysregulation interplay with childhood abdominal tumors

Abdominal tumors (AT) in children account for approximately 17% of all pediatric solid tumor cases, and frequently exhibit embryonal histological features that differentiate them from adult cancers. Current molecular approaches have greatly improved the understanding of the distinctive pathology of each tumor type and enabled the characterization of novel tumor biomarkers. As seen in abdominal adult tumors, microRNAs (miRNAs) have been increasingly implicated in either the initiation or progression of childhood cancer. Moreover, besides predicting patient prognosis, they represent valuable diagnostic tools that may also assist the surveillance of tumor behavior and treatment response, as well as the identification of the primary metastatic sites. Thus, the present study was undertaken to compile up-to-date information regarding the role of dysregulated miRNAs in the most common histological variants of AT, including neuroblastoma, nephroblastoma, hepatoblastoma, hepatocarcinoma, and adrenal tumors. Additionally, the clinical implications of dysregulated miRNAs as potential diagnostic tools or indicators of prognosis were evaluated.

Infantile hepatic hemangioma: current state of the art, controversies, and perspectives

Infantile hepatic hemangioma (IHH) is a common vascular tumor, distinctive for its perinatal presentation, rapid growth during the first year of life, and subsequent involution. Although they generally follow a benign course, some tumors have been reported to undergo malignant transformation. The diagnosis of IHH is based on patient's medical history, physical examination, and imaging. Moreover, the management of this vascular tumor is based on clinical presentation and includes observational, medical, surgical, and radiological interventional treatment options. The present review presents the currently available data in the literature on the diverse aspects of the terminology, epidemiology, clinical presentation, pathogenesis, diagnosis, indications for surgery, malignant potential, and long-term outcomes of these tumors.Conclusion: No formal guidelines have yet been established for the treatment of these hepatic lesions, and the therapeutic strategies implemented vary widely from simple observation to medical, radiological, and surgical interventions in the prism of multidisciplinary teams.What is Known:• Infantile hepatic hemangioma is the most common benign tumor of the liver in infancy, but despite its benign nature, it can present with life-threatening complications.• The treatment strategies range from simple observation to a series of medical, surgical, and radiological interventions.What is New:• This review gives an overview of the developments and current status about the management of IHH.• The aim of this study is to clear up the confusion and controversy that exists about terminology, diagnosis, and treatment of IHH.

A Simulation Paradigm for Evaluation of Subtle Liver Lesions at Pediatric CT: Performance and Confidence

PURPOSE

To create and validate a systematic observer performance platform for evaluation of simulated liver lesions at pediatric CT and to test this paradigm to measure the effect of radiation dose reduction on detection performance and reader confidence.

MATERIALS AND METHODS

Thirty normal pediatric (from patients aged 0-10 years) contrast material-enhanced, de-identified abdominal CT scans obtained from July 1, 2012, through July 1, 2016, were retrospectively collected from the clinical database. The study was exempt from institutional review board approval. Zero to three simulated, low-contrast liver lesions (≤6 mm) were digitally inserted by using software, and noise was added to simulate reductions in volume CT dose index (representing radiation dose estimation) of 25% and 50%. Pediatric, abdominal, and resident radiologists (three of each) reviewed 90 data sets in three sessions using an online interface, marking each lesion location and rating confidence (scale, 0-100). Statistical analysis was performed by using software.

RESULTS

Mixed-effects models revealed a significant decrease in detection sensitivity as radiation dose decreased (P < .001). The mean confidence of the full-dose and 25% dose reduction examinations was significantly higher than that of the 50% dose reduction examinations (P = .011 and .012, respectively) but not different from one another (P = .866). Dose was not a significant predictor of time to complete each case, and subspecialty was not a significant predictor of sensitivity or false-positive results.

CONCLUSION

Sensitivity for lesion detection significantly decreased as dose decreased; however, confidence did not change between the full-dose and 25% reduced-dose scans. This suggests that readers are unaware of this decrease in performance, which should be accounted for in clinical dose reduction efforts.Keywords: Abdomen/GI, CT, Liver, Observer Performance, Pediatrics, Perception Image© RSNA, 2019.

Clinicopathologic characteristics of de novo nodular regenerative hyperplasia in pediatric liver transplant

Liver NRH is seen in all patients age; however, more frequently in those over the age of 60 years and associated with multiple systemic diseases. In liver allograft recipients, the development of DnNRH has been linked with the use of azathioprine or vascular abnormalities. We present the clinicopathologic characteristics of 17 pediatric patients who underwent liver transplantation and subsequently developed DnNRH. The patients were divided into early and late onset depending if DnNRH was diagnosed within or beyond 4 years after transplant. Eight patients (47%) presented as early onset, of which two had normal ultrasound at time of diagnosis. One patient (12.5%) with early onset lost the graft secondary to DnNRH. Nine patients (53%) presented as late onset, of which two (22%) had normal ultrasound at time of diagnosis. Two patients (25%) of the late onset lost their graft secondary to chronic rejection and DnNRH. Two patients (12%) died secondary to cytomegalovirus pneumonitis and pancolitis. Furthermore, both groups presented with symptoms differing from the adult population in prior studies and were not associated with the use of azathioprine or vascular abnormalities. Interestingly, episodes of acute cellular rejection were more common in the early-onset group compared to the late-onset group. In conclusion, DnNRH in the pediatric age group has a different clinical presentation, possibly reflecting a different pathogenesis compared to the adult population.

A rare case of accessory spleen torsion in a child diagnosed by ultrasound (US) and contrast-enhanced ultrasound (CEUS)

INTRODUCTION

Accessory spleen, also known as supernumerary spleen or splenunculum, is a congenital anomaly of the spleen due to a fusion defect during the embryogenesis. Usually it is detected casually during an ultrasound (US) examination of the abdomen and it is asymptomatic.

CASE REPORT

RESULTS: We present a case of a 12 years old male patient, with 2-days history of left abdominal pain, without fever, gastrointestinal or genitourinary symptoms. The day before our observation, the patient had gone to another hospital, from where he had been discharged with medical analgesic therapy, without any benefit. Blood tests were normal, the Ultrasound abdominal examination showed normal aspect of abdominal organs, but the presence in the left side of a small round parenchymal structure surrounded by hyperechogenic mesenteric fat. We interpreted this image as an accessory spleen, complicated by torsion. As the torsion of accessory spleen is a quite rare occurrence, we carried out a contrast enhanced ultrasound (CEUS) to get more information. CEUS showed the absence of enhancement of the nodular formation, suggestive for a complete lack of vascularization; the spleen was normally enhanced. While the management in case of accessory spleen torsion is non-operative, in this case the patient underwent surgical exploration, due to the persistence of abdominal pain despite the medical therapy, with clinical signs of peritoneal reaction, mimicking an acute abdomen. Surgery confirmed the diagnosis of accessory spleen torsion.

DISCUSSION AND CONCLUSIONS

In conclusion, US is the first diagnostic tool in pediatric abdominal pain and allows to direct the diagnosis; the use of CEUS helps to clarify the US reports, without leaving doubts about the parenchymal vascularization of the abdominal organ involved.

Contrast-enhanced ultrasound in the diagnosis of pediatric focal nodular hyperplasia and hepatic adenoma: interobserver reliability

BACKGROUND

Focal nodular hyperplasia and hepatic adenoma are rare liver tumors in which specific features on contrast-enhanced ultrasound (US) have been reported but are little known in children.

OBJECTIVE

To assess the interobserver agreement in diagnosing and differentiating focal nodular hyperplasia and hepatic adenoma in children using established adult contrast-enhanced US characteristics.

MATERIALS AND METHODS

Thirty children with a definite or probable diagnosis of focal nodular hyperplasia or hepatic adenoma on magnetic resonance imaging (MRI)/histology who underwent contrast-enhanced US studies were included. Typical and additional contrast-enhanced US features of focal nodular hyperplasia and hepatic adenoma were included. The lesions were classified as definite/probable focal nodular hyperplasia, definite/probably hepatic adenoma or unclassified. The interobserver kappa of contrast-enhanced US characteristics was calculated.

RESULTS

Focal nodular hyperplasia and hepatic adenoma in children demonstrate contrast-enhanced US characteristics similar to those in adults. Among the nine lesions with confirmed histological diagnosis, correct diagnosis was made in 7 (77.8%) based on contrast-enhanced US criteria. Two lesions were unclassified by both observers due to a mixed arterial filling pattern. Interobserver kappa for contrast-enhanced US diagnosis was 0.64 (P<0.0001).

CONCLUSION

There is a good interobserver kappa for separating focal nodular hyperplasia from hepatic adenoma in children using established adult contrast-enhanced US features.