1-Abdominal masses are common in infants and children,
2- and imaging plays an important role in their diagnosis
and management.
3-Plain radiographs provide clues to the location of the
mass and the presence of calcifications.
4-US is generally the most valuable procedure for the
initial evaluation.
5-US differentiates cystic from solid masses, indicates the
organ of origin, and commonly suggests the diagnosis.
6- CT or MR may be needed when the mass is large,
poorly defined, or obscured by bowel gas.
1-Pseudomasses may be caused on
abdominal radiographs by a fluid-filled
stomach, urinary bladder, or a loop of
intestine.
2-Structures outside the abdomen, such as
large skin lesions, umbilical hernias, and
meningomyelocele, can also mimic an
abdominal mass.
3-The most common abdominal masses in
infants and children are enlarged kidneys
caused by hydronephrosis or cystic renal
disease.
Renal and Adrenal Masses
Large Kidneys
1-Unilateral enlargement of a kidney results from
hydronephrosis, multicystic dysplastic kidney, renal vein
thrombosis, or renal tumors .
2-Bilateral renal enlargement can be seen with
hydronephrosis, polycystic kidney disease, storage
diseases, and glomerulonephropathies, including nephrotic
syndrome.
3- Bilateral renal enlargement caused by neoplasms is less
common, although leukemia or lymphoma may infiltrate
the renal parenchyma bilaterally
Nephroblastomatosis
1-Small islands of primitive metanephric blastema,
which are thought to be a precursor of Wilms tumor,
commonly exist in the kidneys of the normal newborn
infant.
2- These primitive cells usually spontaneously regress
by 4 months of age.
3- A diffuse and proliferative form of persistent renal
blastoma is referred to as nephroblastomatosis.
The abnormal tissue can form as multiple discrete
nodules within the renal parenchyma or may
completely replace the renal cortex. Nephroblastomatosis appears on CT or IV pyelogram
as bilateral lobulated and enlarged kidneys with
marked compression, stretching, and distortion of the
pelvicaliceal structures

FIGURE 52.55. Nephroblastomatosis. A. The kidneys are
massively enlarged, with lobulated thickening of the
parenchyma and stretching and compression of the
collecting structures. B. T1WI in another patient shows
multiple peripheral Wilms tumors (arrows) in a child with
nephroblastomatosis.
On US, the kidneys are enlarged, lobular, and
echogenic, or enlarged with diffuse hypoechoic
thickening of the cortex. In such cases, Wilms
tumor should be suspected. Nephrogenic rests
are more likely to appear cortical, tend to be
homogeneous, and are of low echogenicity on
US, low attenuation on CT, and low signal
intensity on T1WIs . Small, focal nephrogenic
rests smaller than 1 cm are difficult to visualize
by US and are better evaluated with contrastenhanced CT or T1WI
Wilms tumor is the most common renal neoplasm
of childhood (81). It arises from the primitive
metanephric epithelium and demonstrates varied
histologies, which are classified into favorable
and unfavorable groups. The prognosis is
dependent on tumor histology and resectability,
with survival above 90% for tumors with
favorable histology. Wilms tumor presents as a
nontender, rapidly growing, unilateral abdominal
mass in a young child. The mean age of
presentation is 3 years. Bilateral tumors are found
in 10% of patients—more commonly in children
with associated congenital anomalies or
nephroblastomatosis
On US, Wilms tumor characteristically is a well-defined,
predominantly solid mass arising from the kidney
Hypoechoic or anechoic areas within the tumor represent
necrosis. Hydronephrosis is commonly present. Wilms tumor
has a propensity to extend into the renal vein, inferior vena
cava, and RA; all of these structures must be evaluated
preoperatively CT is used to evaluate large tumors and the
lungs, which are a common site of metastasis. Either CT or
MR can be used to exclude small masses in the contralateral
kidney, which can be difficult to identify with US .
Calcification is uncommon in Wilms tumor.
FIGURE 52.56. Wilms Tumor. A. The large, heterogeneous, left-sided tumor (T)
shows a well-defined, enhancing rim (arrows). Note that the left renal
parenchyma is stretched along the margin of the mass (claw sign), indicating an
intrarenal mass. B. Tumor extension into the inferior vena cava (arrow) in
another patient is seen with US. C. CT scan in a different child shows a large,
partially cystic Wilms tumor (T) on the left and identifies a smaller Wilms tumor
mass in the contralateral kidney (arrows).
Renal cell carcinoma is very rare in young
children but sometimes occurs in older
children and adolescents. Like Wilms
tumor, renal cell carcinoma usually presents
as an asymptomatic abdominal mass,
although hematuria is sometimes present.
Hypertension is less common with renal cell
carcinoma than with Wilms tumor. The
imaging characteristics of renal cell
carcinoma are indistinguishable from those
of Wilms tumor.
Other malignant tumors are rare in children.
Clear-cell sarcoma and rhabdoid tumor of the
kidney are highly aggressive neoplasms that were
once considered variants of Wilms tumor. They
are distinguished by a very poor prognosis and
different metastatic patterns. The primary tumors
have an imaging appearance identical to that of
Wilms tumor, but bone metastases are common in
clear-cell sarcoma, and rhabdoid tumor is
associated with brain metastases and second
intracranial primaries. Metastatic disease to the
kidneys is uncommon. The kidneys may be
infiltrated by leukemia or lymphoma, causing
diffuse enlargement or multiple masses

FIGURE 52.57. Renal Lymphoma. Multiple
nodular tumor masses (arrows) are visible
within the enlarged kidney on US.
Mesoblastic nephroma is the most
common renal tumor of the
neonate. Like Wilms tumor,
mesoblastic nephroma arises
from the metanephric blastema,
and these tumors are
indistinguishable on US.
Although mesoblastic nephroma
is usually considered benign,
metastasis occasionally occurs
(82,83).
Adrenal Hemorrhage
Adrenal masses characteristically cause
downward and outward displacement of the
kidney. In the newborn, the most common cause
of adrenal enlargement is adrenal hemorrhage.
Predisposing factors include large babies,
obstetric trauma, neonatal sepsis, and hypoxia.
The infants may present with an abdominal
mass, jaundice, hypotension, or anemia, but
small hemorrhages may go unnoticed.
Hemorrhage occurs more frequently on the right
and is occasionally bilateral. Older children
develop adrenal hemorrhage as a result of
accidental trauma, child abuse,
meningococcemia, or anticoagulant therapy
US is an ideal modality for evaluating
adrenal hemorrhage. The normal
adrenal gland in the newborn is larger
and more easily visualized than that of
the adult. The gland appears as an
inverted V–shaped structure with an
echogenic central region and a
peripheral hypoechoic zone.
FIGURE 52.58. Normal Adrenal Gland.
Note the characteristic “Y―shape
(arrow) of the normal adrenal gland
sitting astride the kidn
Hemorrhage enlarges the gland and causes loss of
the V shape. Initially, the hematoma resembles a
solid, echogenic mass . As the hemorrhage
resolves, it becomes increasingly hypoechoic,
starting in the central region and progressing
peripherally . The hematoma decreases in size
within the first week and sometimes calcifies. The
calcifications begin around the rim of the gland,
but eventually a small, completely calcified gland
remains. Adrenal insufficiency rarely develops.
Adrenal hemorrhage may be complicated by
compression of the kidney, renal vein thrombosis,
or infection.
FIGURE 52.59. Adrenal Hemorrhage. A.
In the early stages, hemorrhage into the
adrenal gland presents as an echogenic
suprarenal mass (arrows). B. A resolving
adrenal hemorrhage in a different infant
appears cystic centrally on US (arrows).
Neuroblastoma belongs to a group of neural crest origin
tumors that range from the benign ganglioneuroma to the
highly malignant neuroblastoma. Neuroblastoma arises
from the adrenal gland or from sympathetic ganglia in the
retroperitoneum, posterior mediastinum, neck, or pelvis. It
is a neoplasm of early childhood, presenting in children
younger than 5 years of age. Most children present with
advanced disease and large abdominal masses. Symptoms
are often related to bone metastases or intraspinal
extension. In contrast to Wilms tumor, neuroblastoma is a
poorly marginated mass that frequently extends across the
midline and into the chest. The kidney may be invaded,
causing the tumor to be mistaken for an intrarenal mass
(Fig. 52.60A
FIGURE 52.60. Neuroblastoma. A. Note the large, ill-defined,
heterogeneous left abdominal mass (arrows). The mass crosses the
midline and secondarily invades the left kidney. B. Radiograph
shows a large soft tissue mass that displaces the right kidney
inferiorly. Irregular, amorphous calcifications are seen within the
mass (arrow). C. MR in a different patient shows a large mass (M)
displacing the left kidney (K). A second tumor mass is identified
adjacent to the spine in the right upper hemithorax (arrow). D.
Axial T1WI in another patient clearly shows tumor extension into
the spinal canal (arrows).
Most neuroblastomas appear echogenic and heterogeneous. In some
cases, a characteristic echogenic nodule can be identified within the
larger part of the tumor mass. CT and MR can be used to better define
the extent of involvement of large tumors and to detect metastatic
deposits . Neuroblastoma metastasizes to the liver, lymph nodes, and
bone marrow. MR demonstrates intraspinal extension , bone marrow
infiltration, and encasement of blood vessels without using IV
contrast. Skeletal metastases are shown with technetium bone
scintigraphy. Iodine-131-meta-iodobenzylguanidine is a tracer that
resembles norepinephrine and is metabolized by neuroblastoma,
pheochromocytoma, and other catecholamine-producing tumors.
Octreotide is a ligand for G-protein receptor cell membranes. These
two tracers have improved detection of primary tumor and metastases
in some cases
Diffuse adrenal enlargement occurs with
adrenocortical hyperplasia, which causes adrenogenital
syndrome. The enlarged adrenals may have an
undulating configuration, described as cerebriform .
Marked, reversible adrenal enlargement is seen in
infants treated with adrenocorticotropic hormone for
infantile spasm
Wolman disease is a rare lipidosis that results in
enlarged, densely calcified adrenal glands. Plain films
are usually diagnostic. Wolman disease is usually fatal
at an early age

FIGURE 52.61. Congenital Adrenal Hyperplasia.
Note the undulating configuration of the enlarged
adrenal gland
Hepatobiliary Masses
A variety of cystic and solid masses may arise from the liver and
biliary tract in children Most conditions can be differentiated with
US.
Acute hydrops of the gallbladder is a poorly understood condition
probably caused by transient obstruction of the cystic duct. It has
been associated with the mucocutaneous lymph node syndrome
(Kawasaki disease); however, in many cases the cause is unknown.
US shows a markedly enlarged, tender gallbladder with a thin wall.
Acute acalculous cholecystitis causes similar gallbladder
enlargement, but the gallbladder distension is less pronounced and
gallbladder wall thickening is present. Transient distension of the
gallbladder sometimes occurs in the neonate, particularly in
premature infants. Prolonged total parenteral nutrition and sepsis
have been implicated as possible etiologic factors
Appendiceal abscess
Genitourinary
Ovarian cyst
Abdominoscrotal hydrocele
Hydrometrocolpos
Urachal cyst
Teratoma/dermoid cyst
Miscellaneous
CSF pseudocyst
Choledochal cysts are congenital malformations of
the intrahepatic or extrahepatic bile ducts. Multiple
factors probably lead to the development of
choledochal cysts, but the majority of cysts are
associated with an anomalous junction of the
common bile duct and pancreatic duct (abnormal
pancreatobiliary junction [APBJ]). The APBJ allows
pancreatic enzymes to reflux into the common bile
duct, which may lead to inflammation and
weakening of the bile duct wall. Jaundice, pain, and
a right upper quadrant mass comprise the classic
triad of findings seen with a choledochal cyst.
Young infants more commonly present with
fluctuating jaundice, pain, and fever
The most common type of choledochal cyst (type 1) is a
localized, fusiform or saccular dilation of the common
bile duct below the cystic duct. Choledochal cysts are usually
diagnosed by US, appearing as a cystic mass in the porta
hepatis, separate from the gallbladder and associated with
dilated intrahepatic ducts Hepatobiliary scintigraphy confirms
that the cyst communicates with the biliary tract, aiding in
differentiation from other cystic abdominal masses MR
cholangiopancreatography may provide more detailed
information about bile duct anatomy and anatomic
relationships to adjacent structures

FIGURE 52.62. Choledochal Cyst. A. US shows a large, multilobulated
anechoic cyst (C) that is adjacent to, but separate from, the gallbladder
(arrows). B. Cholangiography confirms the presence of a large intrahepatic
choledochal cyst (arrows) involving the right hepatic duct. GB, gallbladder. C.
CT scan of a different child shows a well-defined cyst in the porta hepatis
Hepatic cysts are less common in infants and children
than in adults. Solitary congenital cysts of the liver are
usually encountered as an incidental finding at US or
CT. The cyst walls are thin and the fluid is anechoic on
US. Some cysts are very large and pedunculated, and
their hepatic origin may be difficult to ascertain.
Multiple hepatic cysts occur in patients with
autosomal dominant polycystic disease. Acquired
hepatic cysts may be solitary or multiple and are most
commonly of infectious origin (Fig. 52.63). Resolving
hematoma of the liver may also appear as a welldefined cystic lesion

FIGURE 52.63. Candida Abscess of the Liver. Two
irregular cystic collections with peripheral
echogenicity are liver abscesses in this newborn
infant with Candida sepsis
Hemangioendothelioma is the most common benign liver tumor
encountered in infancy . This vascular lesion may be solitary or
multiple and is associated with cutaneous hemangiomas in 40% of
cases. Hemangioendothelioma may be complicated by highoutput cardiac failure,
hemorrhage, jaundice, hemolytic anemia, or thrombocytopenia
because of sequestration of platelets within the tumor. The typical
sonographic appearance is a solid or complex mass associated
with large feeding and draining vessels, seen best with color
Doppler US The mass is well circumscribed and low in
attenuation on CT and shows predominantly peripheral contrast
enhancement. High signal intensity is seen on T2WIs, with
multiple flow voids throughout the lesion representing vessels.
The tumor may be treated with steroids, but arterial embolization
or surgery may be needed in more symptomatic cases.
FIGURE 52.64. (Color Plates) Vascular
Neoplasms of the Liver. A. This solitary
hemangioendothelioma appears echogenic
on US, with multiple hypoechoic vascular
channels. B. Color flow Doppler shows the
large feeding and draining vessels of the
hemangioendothelioma. C. Multiple
sonolucent liver masses (arrows) represent
hemangioendotheliomas. D. Arteriography
demonstrates the marked vascularity
(arrows) of a hemangioendothelioma.
Mesenchymal hamartoma is an uncommon
benign tumor seen most often in infants and
young children. Hamartomas are usually solitary
and predominantly cystic, with multiple thin
septations and intervening nodules of solid
tissue apparent on US. CT shows multiple areas
of low attenuation within the tumor mass.
Hepatic adenomas are rare in childhood but have
been reported in association with Fanconi
anemia, glycogen-storage disease type 1, Hurler
disease, and severe combined immunodeficiency.
Focal nodular hyperplasia presents as a masslike
lesion that most likely represents a hyperplastic
response to a congenital arteriovenous
malformation. Scintigraphy using sulfur colloid
demonstrates normal to increased tracer uptake in
many cases, differentiating it from adenomas that
do not concentrate the tracer. On CT, the lesions
show early phase enhancement but become
isoattenuating with the liver on delayed images.
An enhancing central scar may be seen.
Metastatic Disease
Neuroblastoma is the most
common childhood tumor to
metastasize to the liver, followed
by lymphoma, leukemia, and
Wilms tumor. Metastatic lesions
are usually multiple, and their
imaging appearance is generally
nonspecific
Hepatoblastoma is a tumor
of early childhood,
presenting before 3 years of
age . The tumor is more
common in children with
Beckwith-Wiedemann
syndrome and familial
adenomatous polyposis
FIGURE 52.65. Hepatoblastoma. A CT scan
demonstrates a large inhomogeneous tumor
within the right lobe of the liver (arrows).
Hepatocellular carcinoma is more commonly seen in older children and
adolescents. Sonographically, these tumors appear as single or multiple
hyperechoic lesions, sometimes containing hypoechoic or anechoic areas
because of hemorrhage or necrosis. Invasion of the hepatic or portal veins
may be identified. On CT, the tumors appear as low-attenuation lesions with
variable contrast enhancement. MR is comparable with CT for the initial
diagnosis of these tumors; however, MR is more sensitive in the detection of
postoperative tumor recurrence . MR angiography with three-dimensional
reconstruction helps to evaluate tumor blood supply for surgical planning.
Complete resection is required for survival, and orthotopic liver
transplantation has been successful in some advanced cases of
hepatoblastoma that would otherwise be unresectable. PET-CT promises to
be a more sensitive
modality for identifying tumor metastases and local recurrence (
Other less common primary malignant tumors in
children include undifferentiated (embryonal)
sarcoma and embryonal rhabdomyosarcoma of
the biliary ducts. The latter tumor typically
occurs in children between 2 and 5 years of age.
When the tumor originates in a major bile duct,
the patient presents with jaundice. Those tumors
that originate within the intrahepatic ducts
cannot be differentiated from other primary
malignancies of the liver
Splenic Lesions
Splenomegaly is a relatively common cause
of a left upper quadrant mass in children.
Splenic enlargement is most often secondary
to a systemic illness. Common causes include
hematologic diseases, infections, portal
hypertension, and infiltrative diseases
(mucopolysaccharidoses,
reticuloendothelioses, leukemia, and
lymphoma). P.1320
The imaging characteristics are usually
nonspecific and insufficient for diagnosing
the cause of splenomegaly.
In the newborn and young infant,
splenomegaly most often occurs because of
bacterial sepsis and infection. Hepatomegaly
is generally also present. In older children,
infections such as infectious mononucleosis,
typhoid fever, and catscratch fever are more
common. Multiple small, poorly defined
hypoechoic lesions can be seen with US in
granulomatous splenic infection such as
Bartonella (catscratch fever), tuberculosis, or
fungal infection. Splenic abscess is
uncommon in children and is most often
associated with an impaired immune system
FIGURE 52.66. Catscratch Disease. US
demonstrates the multiple hypoechoic nodules in
the spleen (arrows) that are characteristic of this
infection
Cystic masses of the spleen are
uncommon and include congenital
epidermoid cysts, posttraumatic
pseudocysts, and echinococcal cysts .
Cystic lymphangiomatosis is a benign
lymphatic malformation with a
characteristic multiloculated cystic
appearance. The lesion may contain
calcification and enhances on CT
Splenic Neoplasms
Primary neoplasms of the spleen (hemangioma, hamartoma,
angiosarcoma) are rare. Lymphoma and leukemia commonly
involve the spleen. However, splenic involvement with
lymphoma does not necessarily result in splenic enlargement.
Conversely, children with leukemia or lymphoma may have an
enlarged spleen without neoplastic involvement.
Hemophagocytic lymphohistiocytosis (HLH) is a rare disease
that consists of overactive histocytes and macrophages that
phagocytize the normal cellular structures of the blood. This
condition
is not truly malignant and is probably caused by an
inappropriate immune reaction. HLH usually occurs in infants
under 1 year of age and is characterized by
hepatosplenomegaly, ascites , gallbladder wall thickening,
lymphadenopathy, and pleural effusion .
Splenic Infarction
In children, infarction of the spleen occurs
most often as a complication of sickle cell
anemia, leukemia, Gaucher disease, or
cardiac valvular disease. Acute splenic
infarction results in decreased echogenicity
on US and diminished or mottled
enhancement on CT. Rarely, a poorly fixed
(“wandering―
) spleen may undergo
torsion, leading to infarction