Christopher P. Keup, MDa, Felicia Ratnaraj, BAb, Pooja R. Chopra, BAb, Charles A. Lawrence, MDa and Lisa H. Lowe, MDa∗lhlowe@cmh.edu,     aDepartments of Radiology, Children’s Mercy Hospitals and Clinics, and The University of Missouri—Kansas City, Kansas City, MO, USA; bSchool of Medicine, University of Missouri—Kansas City, Kansas City, MO, USA

∗Corresponding author. Department of Radiology, 2401 Gillham Road, Kansas City, MO 64108.

Hepatic neoplasms constitute approximately 5% to 6% of all pediatric intra-abdominal masses, most of which are malignant. When compared with traditional multiphase computed tomography protocols that are often used in adults, magnetic resonance (MR) imaging is particularly desirable for evaluating liver lesions in children because of the lack of ionizing radiation and superb soft tissue contrast resolution. The goal of this article is to discuss common benign and malignant pediatric hepatic lesions and their key MR imaging findings. Particular emphasis is placed on the utility of new hepatocyte-specific contrast agents to narrow the differential diagnosis.

Keywords

MR imaging • Children • Liver • Masses • Malignancy • Gadoxetate disodium

Key points

Introduction

Primary hepatic neoplasms constitute approximately 5% to 6% of all pediatric intra-abdominal masses, most of which (approximately two-thirds) are malignant.1 Overall, malignant primary hepatic tumors account for 1% to 2% of all childhood cancers.2 It is important, therefore, to systematically approach and accurately characterize hepatic masses to ensure the best possible clinical management strategy (Table 1).

In children, magnetic resonance (MR) imaging is particularly desirable for evaluating liver lesions because of the lack of ionizing radiation and superb soft tissue contrast resolution compared with traditional multiphase computed tomography (CT) protocols. The potential disadvantages of sedation and scan time may be offset by the ability of MR imaging to provide more clinically relevant information when compared with CT. The recent development and implementation of hepatocyte-specific contrast agents (HSA), such as gadoxetate disodium, further strengthens the role of MR imaging in hepatic lesion characterization.

Thus, understanding how pathologic features of hepatic neoplasms are represented in imaging helps the radiologist to better characterize the lesions, which ideally leads to proper work-up and treatment of liver lesions. This article discusses key MR imaging findings of common benign and malignant pediatric lesions (Tables 2 and 3) and focuses on the utility of new HSA to help achieve optimal diagnostic accuracy.

Imaging technique/protocol

MR imaging has some distinct advantages compared with CT and ultrasound (US), which include lack of ionizing radiation (compared with CT), more specific soft tissue characterization, dynamic postcontrast imaging, and more complete evaluation of the biliary system. The lack of ionizing radiation becomes increasingly important when multiphase (including delayed phase) imaging is needed to assess the enhancement characteristics of focal lesions. MR imaging is particularly useful for the characterization of cystic and solid lesions, which are commonly indeterminate in nature at both CT and US, facilitating the formulation of a focused differential diagnosis. Another specific advantage of MR imaging compared with CT is with the evaluation of the biliary tree because bile duct masses, wall thickening, and filling defects are all better visualized with this modality.

Disadvantages of MR imaging include the length of scan time compared with CT or US and its sensitivity to patient motion, possibly necessitating sedation or general anesthesia in pediatric patients. Other disadvantages may include incompatibility with indwelling ferromagnetic devices; susceptibility artifacts and distortion from metallic implants, such as spinal hardware; and limited characterization of calcification/bone. In most clinical imaging situations, the benefits of MR imaging outweigh these disadvantages. The authors’ protocol for imaging of the pediatric liver is presented in Table 4.

Benign pediatric liver lesions