Imaging Findings and Management Strategies for Liver Masses in Children with Predisposition Disorders: A Review by the Pediatric LI-RADS Group

Liver masses in children with underlying systemic disease or a predisposing syndrome can be benign or malignant, ranging from focal fat to hepatocellular carcinoma (HCC). Knowledge of the underlying condition, the pathophysiologic effect on the liver, and the development of liver disease and specific liver lesions allows radiologists to guide imaging with regard to modality and frequency and give recommendations for biopsy when appropriate. In some predisposition disorders, such as Beckwith Wiedemann spectrum, familial adenomatous polyposis syndrome, and tuberous sclerosis complex, established guidelines for imaging screening exist. In many of the syndromes discussed, masses may occur outside of the liver and the liver may not be the primary focus of screening. For other entities, no consensus recommendations exist. Screening recommendations may be based on the risk of development of chronic liver disease. Once cirrhosis occurs, the risk of developing HCC is elevated. The authors summarize the spectrum of liver lesions that may be encountered in children with predisposing syndromes and systemic diseases, the imaging appearance of the lesions with various modalities, and screening guidelines where published. ©RSNA, 2024 See the invited commentary by Rutten and Chavan in this issue.

Can Dynamic Contrast-Enhanced MRI Be Used to Differentiate Hepatic Hemangioma from Other Lesions in Early Infancy?

Background  Confident diagnosis of hepatic hemangioma on imaging can avoid biopsy in early infancy and helps guide conservative management. Purpose  This article aims to determine if dynamic contrast-enhanced magnetic resonance imaging (MRI) can be used to differentiate liver hemangioma from other lesions in infants ≤ 100 days and to determine association of MRI features with hepatic lesions. Methods  MRI performed for liver lesions were retrospectively reviewed to note imaging characteristics and the MRI diagnosis. Final diagnosis was assigned based on pathology in available cases and by corroborative standard of reference including overall clinical features, lab findings, and follow-up. Results  Of 30 infants (18 boys, 12 girls; average age 42.2 days) included, 18 had solitary and 12 had multifocal lesions. Diagnoses in total 33 lesions included hemangiomas (23), hepatoblastoma (6), arteriovenous malformation (2), neuroblastoma metastases (1), and infarction (1). MRI and final diagnosis matched in 94% lesions with almost perfect agreement (kappa 0.86) for reader 1, and matched in 88% lesions with substantial agreement (kappa 0.71) for reader 2. Interobserver agreement for MRI diagnosis was substantial (kappa 0.62). Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MRI in differentiating hemangioma from other lesions were 100, 90, 96, 100, and 97%, respectively. Centripetal (16/23) or flash (5/23) filling were only seen with hemangioma. There was no significant difference in alpha-fetoprotein elevation ( p 0.08), average size ( p 0.35), multifocality ( p 0.38), and intralesional hemorrhage ( p 1) between hemangioma and hepatoblastoma. Conclusion  Centripetal filling on dynamic imaging and absence of washout are characteristic MRI features of hepatic hemangioma that can help to differentiate it from other lesions in early infancy.

Fontan-Associated Liver Disease: A Review

Fontan-associated liver disease (FALD) is a chronic complication of the Fontan procedure, a palliative surgery for patients with congenital heart disease that results in a single-ventricle circulation. The success of the Fontan procedure has led to a growing population of post-Fontan patients living well into adulthood. For this population, FALD is a major cause of morbidity and mortality. It encompasses a spectrum of hepatic abnormalities, ranging from mild fibrosis to cirrhosis and hepatocellular carcinoma. The pathophysiology of FALD is multifactorial, involving hemodynamic and inflammatory factors. The diagnosis and monitoring of FALD present many challenges. Conventional noninvasive tests that use liver stiffness as a surrogate marker of fibrosis are unreliable in FALD, where liver stiffness is also a result of congestion due to the Fontan circulation. Even invasive tissue sampling is inconsistent due to the patchy distribution of fibrosis. FALD is also associated with both benign and malignant liver lesions, which may exhibit similar imaging features. There is therefore a need for validated diagnostic and surveillance protocols to address these challenges. The definitive treatment of end-stage FALD is also a subject of controversy. Both isolated heart transplantation and combined heart-liver transplantation have been employed, with the latter becoming increasingly preferred in the US. This article reviews the current literature on the epidemiology, pathophysiology, diagnosis, and management of FALD, and highlights knowledge gaps that require further research.

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.

Imaging of pediatric liver tumors: A COG Diagnostic Imaging Committee/SPR Oncology Committee White Paper

Primary hepatic malignancies are relatively rare in the pediatric population, accounting for approximately 1%-2% of all pediatric tumors. Hepatoblastoma and hepatocellular carcinoma are the most common primary liver malignancies in children under the age of 5 years and over the age of 10 years, respectively. This paper provides consensus-based imaging recommendations for evaluation of patients with primary hepatic malignancies at diagnosis and follow-up during and after therapy.

Pediatric Hepatic Cystic Lesions: Differential Diagnosis and Multimodality Imaging Approach

When a pediatric hepatic cystic lesion is identified at imaging, the differential diagnosis may be broad, including developmental, infectious, neoplastic, and posttraumatic or iatrogenic causes. The location of a cystic lesion and its number, size, composition, and relationship to the biliary system are features that help in narrowing the differential diagnosis. An incidentally detected simple hepatic cyst is the most commonly encountered. Ciliated foregut cysts are typically located in hepatic segment IVa. The presence of multiple cysts should raise suspicion for fibropolycystic liver disease, a group of related lesions-including biliary hamartoma and choledochal cyst-caused by abnormal embryologic development of the ductal plate. Communication of the cystic lesion with the biliary tree can confirm the diagnosis of choledochal cyst. In a neonate with jaundice, a cystic lesion at the porta hepatis should raise suspicion for choledochal cyst versus cystic biliary atresia. Hepatic abscess can appear cystlike, though typically with internal contents. In an immunocompromised child, multiple cystlike lesions should raise concern for fungal microabscesses. A complex cystic mass in a young child should raise suspicion for mesenchymal hamartoma, which can evolve into undifferentiated embryonal sarcoma if untreated. Hepatic hematoma and biloma can appear cystlike in children with a history of trauma or recent intervention. In neonates with an umbilical vein catheter (UVC), an intrahepatic cyst along the course of the UVC should raise concern for infusate extravasation. Familiarity with imaging findings and clinical features is essential for achieving accurate diagnosis of pediatric hepatic cystic lesions, which in turn can guide appropriate clinical management. Online supplemental material is available for this article. ^©RSNA, 2022.

Liver magnetic resonance imaging: how we do it

Magnetic resonance imaging is used for evaluating focal liver lesions, hepatic vascular diseases, biliary diseases and diffuse liver diseases in children. MRI examinations take a long time, often requiring sedation or anesthesia in smaller children. This makes it essential to understand the concepts and technique necessary to obtain an optimal examination for answering the clinical question while minimizing the need for sedation/anesthesia. We discuss key concepts including appropriate sequence selection, choice of contrast media, dynamic imaging, phases of contrast enhancement and protocol organization.

Imaging and clinical features of pediatric hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is rare in children and there is limited data on its imaging features.

OBJECTIVE

To describe imaging features of pediatric HCC and correlate them with clinical and laboratory findings.

MATERIALS AND METHODS

We retrospectively reviewed imaging in all pediatric HCC cases seen between January 2000 and January 2019. Imaging features defined in LI-RADS (Liver Imaging Reporting and Data System) and tumor extent by PRETEXT (pretreatment extent of disease) criteria were noted by two radiologists. Patient charts were reviewed to collect clinical features, alpha-fetoprotein (AFP) level and pathology findings.

RESULTS

Of the 15 children (7 boys, 8 girls; mean age: 11.8 years, age range: 6-17 years) included in the study, 12/15 had computed tomography, 9/15 had magnetic resonance imaging and 9/15 had ultrasound exams available for review. Pathological types of HCC included classic (11/15, 73%), fibrolamellar (3/15, 20%) and mixed cholangiocarcinoma-HCC (1/15, 7%). Eighty percent occurred de novo in normal liver and 67% showed elevated AFP levels. Arterial phase hyperenhancement was seen in 83% of cases, washout in 86%, capsule in 50% and tumor-in-vein in 33%. The mean tumor size was 9.8 cm and 40% were multifocal on imaging. Staging revealed PRETEXT II tumors in 47%, III in 20% and IV in 33%. There were no PRETEXT I tumors. The two most common PRETEXT annotation factors were portal vein and caudate lobe involvement in 71% and 43% of cases, respectively. Fibrolamellar HCC demonstrated central scar, normal AFP levels and normal background liver.

CONCLUSION

Pediatric HCC are large heterogeneous tumors, as reflected by high PRETEXT staging, and commonly include portal vein and caudate involvement. This affects resectability of these tumors at presentation. Central scar, normal AFP level and normal liver background may help differentiate fibrolamellar HCC from other types of HCC.

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.

Surveillance of Fontan-associated liver disease: current standards and a proposal from the European Society of Paediatric Radiology Abdominal Task Force

Since Francis Fontan first introduced the eponymous technique, the Fontan procedure, this type of surgical palliation has allowed thousands of children affected by specific heart malformations to reach adulthood. Nevertheless, abdominal, thoracic, lymphatic and neurologic complications are the price that is paid by these patients. Our review focuses on Fontan-associated liver disease; the purpose is to summarize the current understanding of its physiopathology, the aim of follow-up and the specific radiologic follow-up performed in Europe. Finally, we as members of the Abdominal Task Force of the European Society of Paediatric Radiology propose a consensus-based imaging follow-up algorithm.

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.

Patterns of enhancement in the hepatobiliary phase of gadoxetic acid-enhanced MRI

A variety of patterns of enhancement of liver lesions and liver parenchyma is observed in the hepatobiliary phase (HBP) of gadoxetic acid-enhanced MRI. It is becoming increasingly apparent that many lesions may exhibit HBP enhancement. Much of the literature regarding the role of gadoxetic acid-enhanced MRI in characterising liver lesions is dichotomous, focusing on whether lesions are enhancing or non-enhancing in the HBP, rather than examining the patterns of enhancement. We provide a pattern-based description of HBP enhancement of liver parenchyma and of liver lesions. The role of OATP1B3 transporters, hepatocyte function and lesion composition in influencing patterns of HBP hyperintensity are discussed.

Surgical Management of Hepatoblastoma and Recent Advances

Hepatoblastoma is the most common childhood liver malignancy. The management of hepatoblastoma requires multidisciplinary efforts. The five-year overall survival is approximately 80% in developed countries. Surgery remains the mainstay of treatment for hepatoblastoma, and meticulous techniques must be employed to ensure safe and effective local control surgeries. Additionally, there have been several advances from both pediatric and adult literature in the way liver tumor surgery is performed. In this review, we highlight important aspects of liver surgery for hepatoblastoma, the management of metastatic disease, and the most current technical advances in performing these procedures in a safe and effective manner.

Rare malignant liver tumors in children

Malignant hepatic tumors in children are rare, comprising 1.3% of all pediatric malignancies. Following hepatoblastoma, hepatocellular carcinoma is the second most common. Other malignant hepatic tumors seen in childhood include those of mesenchymal origin including undifferentiated embryonal sarcoma, angiosarcoma, rhabdomyosarcoma and epithelioid hemangioendothelioma, as well as biliary tumors such as cholangiocarcinoma. Diagnosis can be challenging because of their rarity, and the recognition of distinctive imaging features for certain tumors such as epithelioid hemangioendothelioma and biliary rhabdomyosarcoma can focus the differential diagnosis and expedite the diagnostic process. A complete MRI examination with hepatocyte-specific contrast media and diffusion-weighted imaging helps to focus the differential diagnosis, and, although findings are often nonspecific, in some cases typical features on MRI can be helpful in diagnosis. Histopathological analysis is usually required for definitive diagnosis. Hepatic tumors tend to be aggressive, and full staging is imperative to establish disease extent. Significant proportions are not amenable to upfront surgical resection and often require a multimodality approach including neoadjuvant chemotherapy within a multidisciplinary setting. Facilitating complete surgical resection is usually required for better survival. In this review, we emphasize pathology and imaging features for rare liver tumors that are useful in reaching a prompt diagnosis. We also discuss general clinical findings, prognosis and management of these tumors.

Low b-value (50-100) diffusion-weighted images detect significantly more hyperintense liver lesions in children than T2-weighted images

BACKGROUND

Low b-value (50-100 s/mm²) diffusion-weighted images (low b-value DWI) have been shown to be superior to T2-weighted fast spin echo sequence (T2-W) in detecting liver lesions in adults. There are no such studies assessing this difference in children.

OBJECTIVE

The purpose of the study was to compare the sensitivity of low b-value DWI images and T2-W images in detecting focal liver lesions in children.

MATERIALS AND METHODS

A retrospective review of liver magnetic resonance imaging (MRI) to assess focal liver lesions in 50 children (22 males, 28 females; age: 2 months to 17 years [mean: 10.9 years]) was performed. Two radiologists reviewed both low b-value DWI and T2-W sequences independently on different occasions to note lesions, the smallest lesion size and the location. A consensus reading of the entire MRI examination and a correlation with follow-up, other imaging modalities and pathology in available cases were used to determine the final number of lesions as a reference standard. The average number of lesions per patient detected by both readers on each sequence was compared with each other and with the reference standard using the signed-rank test. The smallest lesions detected by each sequence were compared using the paired t-test.

RESULTS

One hundred seventy hyperintense lesions were identified on consensus review to serve as the reference standard. The average number of lesions identified by both readers on low b-value DWI was 134 (79%) and on T2-W was 95 (56%). There was excellent interobserver agreement for detection of lesions on low b-value DWI (intraclass correlation coefficient [ICC]=0.96 [0.93-0.98]) and T2-W (ICC=0.85 [0.75-0.91]), with slightly better agreement on low b-value DWI. Both readers identified significantly more number of lesions on low b-value DWI compared to T2-W (Reader 1: P=0.0036, Reader 2: P=0.0001). Compared to the reference standard (mean number of lesions: 3.45), T2-W detected significantly fewer lesions (mean number of lesions: 1.91; P=0.0001) while there was no significant difference in lesion detection on low b-value DWI (mean number of lesions: 2.68; P=0.1527). Low b-value DWI and T2-W were not significantly different in identifying the smallest lesion size (Reader 1: P=0.19, Reader 2: P=0.47).

CONCLUSION

Low b-value DWI images are more sensitive than T2-W sequences in detecting hyperintense focal liver lesions in children.

Magnetic resonance imaging features of common focal liver lesions in children

Magnetic resonance imaging (MRI) is commonly used to characterize focal liver masses in the pediatric population. MRI is the preferred modality because of its superior contrast resolution and utility for obtaining functional sequences such as diffusion-weighted imaging (DWI). MR exams performed with a hepatocyte-specific gadolinium-based contrast agent can characterize focal liver lesions, which helps in differentiating a common benign entity such as focal nodular hyperplasia from other liver pathology when the background liver is normal. The most common benign focal lesion is a hemangioma, and metastases followed by hepatoblastoma are the most common malignant lesions. This article can help radiologists become familiar with the pre- and post-contrast imaging features of common pediatric liver masses.

Applications of contrast-enhanced ultrasound in the pediatric abdomen

Contrast-enhanced ultrasound (CEUS) is a radiation-free, safe, and in specific clinical settings, highly sensitive imaging modality. Over the recent decades, there is cumulating experience and a large volume of published safety and efficacy data on pediatric CEUS applications. Many of these applications have been directly translated from adults, while others are unique to the pediatric population. The most frequently reported intravenous abdominal applications of CEUS in children are the characterization of focal liver lesions, monitoring of solid abdominal tumor response to treatment, and the evaluation of intra-abdominal parenchymal injuries in selected cases of blunt abdominal trauma. The intravesical CEUS application, namely contrast-enhanced voiding urosonography (ceVUS), is a well-established, pediatric-specific imaging technique entailing the intravesical administration of ultrasound contrast agents for detection and grading of vesicoureteral reflux. In Europe, all pediatric CEUS applications remain off-label. In 2016, the United States Food and Drug Administration (FDA) approved the most commonly used worldwide second-generation ultrasound contrast SonoVue®/Lumason® for pediatric liver and intravesical applications, giving new impetus to pediatric CEUS worldwide.