|Year : 2020 | Volume
| Issue : 3 | Page : 176-185
Imaging Appearances of Pediatric Hepatic Masses − A Review
Shruti Mittal, Sapna Singh, Radhika Batra
Department of Radiodiagnosis, Maulana Azad Medical College and Lok Nayak Hospital, Delhi, India
|Date of Submission||10-Jul-2020|
|Date of Decision||18-Jul-2020|
|Date of Acceptance||23-Jul-2020|
|Date of Web Publication||16-Dec-2020|
MBBS, MD Shruti Mittal
Department of Radiodiagnosis, Maulana Azad Medical College and Lok Nayak Hospital, Delhi
Source of Support: None, Conflict of Interest: None
In the pediatric population, a wide spectrum of focal liver lesions is seen, which can be categorised into congenital, inflammatory or neoplastic origin. Majority of the patients with focal liver masses present with abdominal pain, abdominal distention or palpable abdominal lump. However, some lesions can be detected incidentally. After physical examination and clinical history, imaging plays a vital role in evaluating pediatric patients with suspected focal liver lesions. Abdominal radiography may provide some imaging findings suggesting the presence of focal hepatic mass such as hepatomegaly, presence of calcification and displacement of bowel loops. Ultrasound is the first line imaging modality as it does not involve ionising radiation. It can detect, characterise and provide the extent of lesion. However, computerised tomography and magnetic resonance imaging are performed subsequently for further characterisation of liver lesions on the basis of morphology, vascularity, enhancement pattern and for detection of associated metastases in malignant neoplasms. In this review article, we aim to describe the imaging appearances of various benign and malignant hepatic mass lesions in the paediatric age group and to provide differential diagnosis for liver lesions in a child on the basis of available imaging and clinical data. Imaging is therefore essential for making prompt and accurate diagnosis which further helps in appropriate treatment and optimal patient management.
Keywords: Hepatic masses, imaging appearances, paediatric
|How to cite this article:|
Mittal S, Singh S, Batra R. Imaging Appearances of Pediatric Hepatic Masses − A Review. MAMC J Med Sci 2020;6:176-85
| Introduction|| |
A wide spectrum of liver lesions is seen in paediatric age group, which can be categorised into congenital, neoplastic and inflammatory origin. However, there are certain extrahepatic lesions which can simulate focal hepatic masses.
Characterisation of these lesions based on imaging appearances plays a crucial role in making prompt and accurate diagnosis, which further helps in planning optimal patient management. Some lesions can be discovered incidentally, however, most of the patients with hepatic masses present with abdominal distension, abdominal pain or a palpable abdominal lump.
Plain radiographs may have some role in detecting hepatomegaly, calcifications and displacement of bowel loops.
Ultrasound is the first line imaging modality, as it is free of ionising radiation and helps in detection and characterisation of focal hepatic lesions. Detection of liver lesion on ultrasound indicates further evaluation. Multidetector Computed tomography (CT) and multiphasic magnetic resonance imaging (MRI) allows further characterisation of liver lesions on the basis of morphology, vascularity, enhancement pattern and certain specific functional characteristics.
| Benign Lesions|| |
Infantile hepatic haemangioma
Formerly, this was known as infantile hemangioendothelioma. Infantile hepatic hemangioma is the most common benign hepatic tumor of infancy. Ninety percent of the cases are diagnosed within first 6 months of life. They have a slight female predilection. It is a vascular neoplasm and association with haemangiomas involving other sites like skin, thorax and adrenal have been reported.
Pathogenesis: Three subtypes have been described focal, multifocal and diffuse types.
The focal subtype is the hepatic form of rapidly involuting congenital hemangioma and is negative for glucose transporter protein 1. The multifocal subtype is hepatic counterpart of simple cutaneous haemangioma and is often associated with multiple cutaneous hemangiomas. It is positive for glucose transporter protein 1. In the diffuse subtype, the entire liver parenchyma is replaced by multiple hemangiomas. Patients present with a large abdominal mass and high output failure due to arteriovenous shunting.
Ultrasound: The lesions show variable echogenicity (may be echogenic, hypoechoic or anechoic) with echogenic septa within [Figure 1]A. On Color doppler imaging, there is an increase in peripheral vascularity [Figure 1]B. Also, there is narrowing of abdominal aorta below the origin of the celiac axis, a dilated celiac axis and common hepatic artery with prominent draining hepatic veins.
|Figure 1 Infantile hepatic hemangioma. Transverse ultrasound (A) image in a three month old female shows multiple well defined hypoechoic lesions within the liver and colour doppler B) shows evidence of significantly increased peripheral vascularity. Computed tomography (CT) images of the same reveal multiple well-defined lesions in both lobes of the liver appearing hypoattenuating on non-contrast CT(C) and intensely enhancing on contrast enhanced CT(D) in a case of infantile hepatic hemangioma.|
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CT: Non contrast scans may reveal hepatomegaly with multiple hypodense lesions [Figure 1]C. Calcification can be seen in 40 percent of cases. Contrast scans reveal peripheral nodular and centripetal enhancement followed by prolonged and persistent enhancement [Figure 1]D. CT angiography reveals dilated celiac axis artery and narrowing of aorta below its origin.
MRI: The lesions are hypointense on T1W images and hyperintense on T2W images with contrast enhancement pattern similar to that of hemangiomas.
Mesenchymal hamartoma is a benign cystic developmental lesion. It is the second most common benign liver lesion in the pediatric population. Usually occurs in children under 2 years of age with male predominance. The most common presentation is painless abdominal distention. Mesenchymal hamartoma has been diagnosed prenatally and is associated with hydrops.
Ultrasound: Usually seen as a well circumscribed multiseptated multilocular solid cystic lesion [Figure 2]A. The lesion can rarely have a solid appearance, if the mesenchymal component predominates. Color Doppler imaging shows little blood flow which is limited to solid portions and septa.
|Figure 2 Mesenchymal hamartoma. USG image (A) shows a well-defined multiloculated cystic lesion with multiple septae replacing the liver. Contrast enhanced coronal (B) images of another patient showing hypodense lesion with multiple enhancing septations within. T2 axial (C) and post contrast(D) MR images showing a hyperintense lesion on T2 with enhancing septations within.|
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CT: It is seen as a multiseptated fluid attenuation lesion with the stromal component appearing hypoattenuating to the surrounding liver, with contrast enhancement of thin internal septations and solid component [Figure 2]B. No /o calcification or hemorrhage seen within the lesions.
MRI: Cystic component of the lesion is markedly hyperintense on T2W while the stroma appears hypointense on both T1 and T2W images with enhancement of the septae within [Figure 2]C, 2D.
Focal nodular hyperplasia (FNH)
Mostly seen in adult women but uncommonly occurs in young children and adolescents.
FNH is a benign epithelial liver tumor. In children, the lesion is typically diagnosed in 2 to 5 years age, accounts for 4 percent of primary hepatic tumors in children from birth to 20 years. Marked female predominance is seen. The lesion is mostly detected incidentally at imaging or in surgical specimen.
Ultrasound: FNH appears as a homogeneous well-described solid hepatic mass with a central hypoechoic scar [Figure 3]A, 3B. On Color Doppler imaging, the lesion reveals increased blood flow in the central scar giving spoke wheel pattern.
|Figure 3 Focal nodular hyperplasia. ultrasound images (A and B) in this 3 yr old child shows a well-defined lesion in the region of Lt. lobe of liver appearing isoechoic to the liver parenchyma with central hyperechoic area within. T2 weighted axial (C) images in the same patient showing a large lesion in left lobe appearing iso-hyperintense with characteristic central stellate T2 hyperintensity suggesting a central scar. On contrast enhanced scan (D), the mass shows homogenous enhancement with non-enhancing radiating central stellate scar suggesting focal nodular hyperplasia.|
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CT: On non-contrast scans, FNH is similar to density in normal hepatic parenchyma. On contrast enhanced scans, the lesion shows avid enhancement of the lesion in arterial and early portal venous phase and becomes iso-dense to the hepatic parenchyma in the late portal venous and delayed phase. The central stellate scar appears hypoattenuating on arterial and portal venous phase and shows enhancement on delayed images.
MRI: FNH appears homogeneous iso to hypointense to the liver parenchyma with the central scar appearing hypointense on T1W and mildly hyperintense on T2W images [Figure 3]C. After contrast administration, there is early arterial enhancement of the lesion with non-enhancement of the central stellate scar [Figure 3]D. The central scar may show enhancement on delayed scans.
| Malignant Tumours|| |
Hepatoblastoma is the most common primary hepatic malignancy of epithelial and mesenchymal cell origin in pediatric population., Ninety percent of cases are seen in children younger than 5 years of age with a slight male predominance. Hepatoblastoma is associated with several syndrome like familial adenomatous polyposis, type 1A glycogen storage disease, Gardner syndrome and Beckwith-Wiedemann syndrome More Details. A strong association between birth weight and hepatoblastoma is observed, with the prevalence of hepatoblastoma being inversely proportional to birth weight.
Most of the pediatric patients manifest as painless abdomen distension and nonspecific symptoms like weight loss and anorexia. Metastasis is common and most frequently involves the lung (10–20 percent of cases). Serum alfa-fetoprotein is the most useful biomarker for hepatoblastoma and is abnormally elevated in 90 percent of the cases.
Abdominal radiographs may be of use in demonstrating hepatomegaly, displacement of bowel loops and presence or absence of calcifications.
USG: The appearance of the tumor depends on its histological type. USG shows a well-defined lobulated inhomogeneous mass lesion, often containing echogenic foci due to calcification and cystic anechoic spaces representing areas of necrosis and hemorrhage [Figure 4]A, 4B. Lobular pattern caused by hypoechoic fibrotic septae may also be seen. Tumors of epithelial origin have homogeneous appearance.
|Figure 4 Hepatoblastoma. ultrasound image (A, B) reveals a lobulated heterogeneous mass lesion containing areas of necrosis and haemorrhage with mild internal vascularity within. Contrast enhanced axial (C) and coronal (D) computed tomography images in a child show a large heterogeneously enhancing hepatic mass lesion with foci of coarse intralesional calcification and small exophytic component suggesting a diagnosis of hepatoblastoma. T2 axial (E) and post-contrast (F) Magnetic resonance images reveal a lobulated lesion appearing hyperintense on T2w images showing heterogeneous post-contrast enhancement.|
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CT: CT most commonly demonstrates hepatoblastoma as a well defined mass, which is hypoattenuating to the liver parenchyma on non-contrast and contrast-enhanced scans. Hepatoblastomas of epithelial origin are homogeneous, whereas mixed tumors are heterogeneous in attenuation. Calcification may be seen in 40 percent of the cases [Figure 4]C, 4D.
MRI: Hepatoblastoma is seen as lobulated mass that is hypointense on T1 W and hyperintense on T2W with heterogeneous enhancement on post-contrast scans. Fibrotic septae appear hypointense on T1 and T2 weighted images with enhancement on post-contrast scans [Figure 4]E, 4F. Signal characteristics of hepatoblastoma on MRI may vary, if there is associated haemorrhage and necrosis.
The liver is a common site for metastasis. Hepatic metastases are much more common than primary hepatic malignancy. Most common tumors that metastasize to the liver in paediatric age group are neuroblastoma and Wilm’s tumor. Hypovascular liver metastases usually originate from lung and gastrointestinal tract and hypervascular liver metastasis usually arise from thyroid, renal, neuroendocrine or sarcomatous tumors.
USG: On ultrasound, hepatic metastases may show variable echogenicity, can be hypoechoic, hyperechoic or cystic in appearance. The most common presentation is hypoechoic lesion with no distal shadowing or enhancement [Figure 5]A. On Color Doppler imaging, metastases generally do not show intralesional vascularity, but reveal a detouring pattern of vessels around the lesion.
|Figure 5 Metastasis. Ultrasound (A) images reveal multiple variable sized hypoechoic lesions in both lobes of liver having central echogenicity. In another patient, contrast enhanced axial (B) and coronal (C) Computed tomography images show evidence of few, well defined, predominantly hypodense metastatic lesions in the liver with the primary being a large neuroblastoma with coarse calcifications within.|
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CT: Since most of the lesions are hypovascular, usually the protocol is to scan the liver in portal venous phase. On non-contrast scans, most of the liver metastases are hypodense to isodense as compared to the surrounding liver parenchyma. Small lesions are nodular and homogeneous, whereas the larger ones are irregular and inhomogeneous. After contrast administration, metastases from hypovascular tumors show peripheral contrast enhancement seen during the arterial phase and occasionally during the portal venous phase [Figure 5]B, 5C.
Hypervascular liver metastases show moderate to avid post-contrast enhancement during the arterial phase which can persist during the portal phase.
MRI: Hepatic metastases are generally hypointense on T1W and intermediate to hyperintense on T2W images depending on the primary tumor. Hypovascular metastases show peripheral contrast enhancement, whereas hypervascular metastases show early arterial phase enhancement. MRI has a higher diagnostic accuracy than CT scan. Diffusion weighted imaging is useful in detection of metastatic liver lesion.
| Inflammatory Lesions|| |
Pyogenic − bacterial infection
Bacterial infection of the liver may develop from several routes. The most common route is the biliary route owing to the cholangitis secondary to obstructive biliopathy. Other routes include phlebitis of the portal vein or superior mesenteric vein secondary to gastrointestinal infection. Direct extension from contiguous organs, post-traumatic or iatrogenic may also be the source of liver abscess.
Staphylococcus is the most common organism in children while Escherichia More Details coli is the most common in adults. The child may present with fever, pain, nausea, vomiting and malaise.
USG: They appear as well-defined lesions with thick irregular walls having variable echogenicity [Figure 6]A. Debris, septation, fluid-fluid or air-fluid level may also be seen.
|Figure 6 Pyogenic abscess. Ultrasound (A) image shows multiple relatively well defined, heterogeneously hypoechoic ovoid abscesses. In another patient, axial computed tomography (B) image shows a large abscess in the right lobe of liver showing rim enhancement and perilesional edema (double target sign).|
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CT: Abscesses are seen as hypoattenuating lesions with peripheral enhancement and perilesional edema seen on contrast-enhanced scans giving ‘double target sign’ [Figure 6]B. Presence of similar smaller lesions showing coalescence to form larger lesions is also seen giving cluster sign. An air fluid level which is a specific sign for abscess is seen in few cases and may indicate enteric communication or gas-forming organism.
MRI: Abscesses seen as well-defined rounded lesions appearing hypointense on T1W, hyperintense on T2W with peripheral contrast enhancement. The adjacent liver parenchyma may show hyperintensity on T2W images suggesting edema or inflammatory changes. Diffusion weighted images show restricted pattern due to presence of high cellularity and high viscosity of pus.
| Parasitic Infection|| |
Hepatic amoebic abscess is caused most commonly by protozoan Entamoeba histolytica and is one of the most common extra-intestinal manifestation of amoebiasis. The organism reaches the liver through various routes through the portal vein, from the colon, through the lymphatic or by direct extension from the adjacent organs. Amoebic liver abscess is more common is adults as compared to children. Usually children present with diarrhoea, malaise, fever and anorexia. Generally, there is a solitary abscess frequently involving the right lobe of liver.
USG: Amoebic abscess is seen as a round to oval hypoechoic lesion, with fine low-level internal echoes.
CT: Amoebic abscess appears as a hypoattenuating lesion with peripherally enhancing capsule. Lesions in the early stage of development have a solid appearance due to presence of organised contents with older lesions being cystic in appearance. A rim of lower attenuation surrounding the enhancing capsule may be seen giving a characteristic target appearance.
MRI: The abscess cavity appears hypointense on T1W, hypointense on T2W images. The central cavity is surrounded by a rim of high signal intensity corresponding to hyperemic reactive zone showing contrast enhancement.
Hepatic hydatid disease
Hydatid disease is caused most commonly by Echinococcus granulossus. Hydatid disease involves the liver in approximately 75 percent of cases. Humans are intermediate hosts through contact with a definitive host (dog) or through ingestion of contaminated water or vegetables. Once the parasite passes through the intestinal wall to reach the portal venous system or lymphatic system, the liver acts as the first line of defence and is, therefore, the most frequently involved organ.
Usually the child is asymptomatic and the disease can go undiagnosed till adulthood. It can become symptomatic if the infection progresses or the cyst ruptures. Children typically present with fever, nonspecific abdominal pain, peripheral eosinophilia, jaundice and hepatomegaly.
Structure of typical hydatid cyst
The hydatid cyst is a trilaminated structure. The pericyst is the outermost protective layer and is composed of modified host cells. The middle layer is ectocyst that allows passage of nutrients. Endocyst forms the true layer which is the inner germinal layer, where the scolices (the larval stage of the parasite) and the laminated membrane are produced.
Daughter vesicles (brood capsules) are small spheres that contain the protoscolices and are formed from rest of the germinal layer. Fluid within the cyst is antigenic and may also contain scolices. When vesicles rupture within the cyst, scolices pass into the cyst fluid and may form a sediment known as hydatid sand.
Imaging features depend on the stage of cyst growth, i.e. whether the cyst is unilocular, contains daughter vesicles, partially calcified or completely calcified signifying dead parasite.
Calcification can be detected in 20-30% of cases of hydatid cysts, which manifests as a curvilinear or ring-like pattern representing calcification of the pericyst. As a process of healing, dense calcification of all components of the cyst occurs, although the death of the parasite is not necessarily indicated by calcification of the pericyst.
USG: The sonographic appearance of hydatid depends on the stage of evolution and maturity.
- A well-defined anechoic cyst or a cyst with hydatid sand [Figure 7]A, 7C. Multiple echogenic foci due to hydatid sand may be seen within the dependent portion of the cavity referred as the “snowstorm sign” [Figure 7]B.
|Figure 7 Hydatid cyst. Imaging manifestations of hydatid cyst. Ultrasound images (A) trilaminar wall cyst, (B) large anechoic cyst with a scolex, (C) unilocular anechoic cyst, axial computed tomography image (D) detachment of endo-cyst form peri-cyst, (E) cyst within cyst (honeycombing pattern), (F) large cyst with membrane rupture.|
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- Detachment of the endocyst from pericyst can be related to decreasing intracystic pressure, degeneration, host response, trauma or response to therapy. The cyst may appear as a well-defined fluid collection with a localized split in the wall and “floating membranes” within the cavity in case of partial detachment [Figure 7]F. Complete detachment of the membranes inside the cyst has been referred to as the “US water lily” sign as it resembles the radiographic water lily sign in pulmonary cysts.
- Daughter cysts developing from the germinal membrane produces a characteristic appearance of cysts enclosed within a cyst giving ‘honeycomb pattern’ with multiple septa representing the walls of daughter cysts [Figure 7]E.
- Partial or complete calcification of the cyst wall may occur and may be seen as hyperechoic contour with acoustic shadowing.
CT: Echinococcal cyst of the liver appears as a well- defined, round or oval cystic mass of the liver having a near water attenuation [Figure 7]D. Presence of daughter cysts gives a characteristic mutlilocular or honeycomb appearance. The daughter cysts usually contain fluid with a lower attenuation than that of the fluid in the mother cyst. Detachment of the laminated membrane from the pericyst can be visualized as linear areas of increased attenuation within the cyst. Postcontrast scan shows enhancement of internal septation. Calcification of the cyst wall or internal septa are easily detected on CT.
MRI: Hepatic hydatid cysts appear hypointense on T1 and hyperintense on T2-weighted images. The pericyst usually has low signal on T1 and T2-weighted images because it is rich in collagen. The daughter cysts are hypointense to isointense on T1 imaging and isointense on T2W imaging relative to hyperintense hydatid fluid and sand of the mother cyst. The floating membranes seen appear as low intensity structures on T2W. Intraparenchymal rupture of the cyst appears as a defect in the low intensity rim, whereas presence of calcification is seen as signal voids.
Hepatic tuberculosis accounts for less than 1 percent of tubercular infections, being uncommon due to low oxygen tension in liver. Hematogenous route is the most common route of spread to the liver. The disease is more common in young adults. Patients present with nonspecific symptoms like fever, anorexia, weight loss, upper abdominal pain and rarely with jaundice.
Hepatic disease can be classified into parenchymal, serohepatic and tubercular cholangitis. Parenchymal disease is further subdivided into micronodular and macronodular patterns.
Micronodular form: Most common form of the disease usually seen secondary to miliary dissemination with or without concomitant involvement of the lung.
USG: Multiple tiny lesions involve the liver leading to a diffusely hypoechoic appearance of liver. Sometimes the lesions are too small to be resolved on ultrasound and hepatomegaly may be observed as the only imaging finding. Chronic lesions tend to calcify and are seen as echogenic foci with distal acoustic shadowing.
CT: Lesions are seen as micro-abscesses having a central hypodensity with peripheral enhancement on administration of contrast. Chronic lesions are seen as multiple small calcified lesions in the liver. Macronodular form: This is a less common form of parenchymal involvement. Miliary granulomas tend to conglomerate seen as single or multiple complex hepatic masses.
USG: In macronodular form, solitary or multiple variable-sized hypoechoic lesions are seen in hepatic parenchyma on sonography [Figure 8]A. These lesions can mimic bacterial abscesses.
|Figure 8 Hepatic tuberculosis. In a patient with uncommon macronodular tuberculosis, multiple, large, well defined, hepatic lesions noted appearing hypoechoic on ultrasound (A) and hypodense with rim enhancement on computed tomography (B).|
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CT: Solitary or multiple hypoattenuating lesions are seen in the liver with peripheral contrast enhancement. Multiloculated cystic masses or a target sign may be observed which represent a central area of enhancement or calcification surrounded by low attenuation edematous parenchyma [Figure 8]B. This feature is highly suggestive, but not pathognomonic of tubercular abscesses.
Serohepatic Tuberculosis: There is predominant involvement of the subserosal plane of the liver. Imaging reveals peripherally located multiple conglomerate hypodense lesions with thickened enhancing capsule. Associated abdominal lymphadenopathy may be observed.
This occurs due to involvement of the biliary tract primarily or by extrinsic compression by lymph nodes in the periportal region.
Imaging features may vary from bile duct thickening, enhancement of the walls, biliary dilatation and strictures with resultant obstructive biliopathy.
| Conclusion|| |
A wide spectrum of different congenital, neoplastic, and infectious conditions may present as focal hepatic lesions in pediatric patients. Along with the clinical features and physical examination findings, the recognition of specific imaging patterns and characteristics of various focal hepatic masses play a vital role for accurate diagnosis and patient management.
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Conflicts of interest
There are no conflicts of interest.
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