Diagnostic ultrasound ( PDFDrive )

1818 PART V Pediatric Sonography
Spontaneous hemorrhage within the cysts may also occur. 194,195
Renal cysts have also been reported to develop ater liver transplantation.
Patients at risk are at least 10 years posttransplant,
have been treated with cyclosporine, and have impaired renal
function. 196,197
Simple cysts are generally asymptomatic and are much less
common in children than in adults. hey typically appear as a
single mass arising from the renal parenchyma. 198 hey may
occasionally be complicated by infection, hemorrhage, or
calciication. 199
RENAL TUMORS
he most common abdominal masses in the child are of renal
origin: hydronephrosis and MCDK. Solid tumors are less common.
Initial imaging includes sonography and oten a plain ilm of
the abdomen. he site of origin of the mass, its architecture
(cystic or solid), and vascularization can usually be determined
with sonography.
If the mass is cystic and arises from the kidney, the usual
diferential diagnosis is between a hydronephrotic kidney and
MCDK. he coniguration of the cysts on sonography and,
if needed, presence of function on nuclear renography help
distinguish these two entities. If the mass is solid and related to
the kidney, Wilms tumor is the most likely diagnosis. Metastases
and tumoral invasion of the renal vein or inferior vena cava
are sought during the sonographic survey of the abdomen.
Staging of the tumor is usually done with CT or MRI. 200,201
If the kidney is normal and the mass is related to another
organ, the workup continues with imaging that is optimal for
that organ.
Wilms Tumor
Wilms tumor, or nephroblastoma, is the most common intraabdominal
malignant tumor of childhood. Approximately 80%
of patients are aged 1 to 5 years at presentation, with a peak
incidence at 3 to 4 years of age. 202 When the tumor is large, it
may be diicult to diferentiate from neuroblastoma, which
frequently arises from the adrenal gland and occurs in a similar
age group. Wilms tumor is usually bulky and expands within
the renal parenchyma, resulting in distortion and displacement
of the collecting system and capsule. It is usually sharply marginated.
Five percent to 10% of patients have bilateral tumors, and
nephroblastomatosis may be present in both kidneys in children
with unilateral Wilms tumor. Screening is recommended for
children at high risk for the development of Wilms tumor,
including those with hemihypertrophy, sporadic aniridia,
Beckwith-Wiedemann syndrome, WAGR syndrome (Wilms
tumor, aniridia, genitourinary anomalies, and intellectual disability
[mental retardation]), and nephroblastomatosis. 202
Typically, Wilms tumor is a large solid mass distorting the
renal sinus, pyramids, cortex, and contour of the kidney as
depicted with sonography. Although usually quite hyperechoic
and homogeneous, there may be hypoechoic areas that represent
hemorrhage and necrosis. Decreased blood low compared with
the adjacent renal parenchyma is usually seen with color and
power Doppler ultrasound (Fig. 52.62).
Wilms tumor spreads via direct extension into the renal sinus
and peripelvic sot tissues, the lymph nodes in the renal hilum,
and the paraaortic regions. Because extension is possible into
the renal vein, inferior vena cava, right atrium, and liver, these
areas should also be examined for the presence of tumor (Fig.
52.63). Color and spectral Doppler sonography are useful in
detecting residual low around a tumor clot, as well as tumor
arterial signals both from the periphery of the tumor and from
within the tumor thrombus. he opposite kidney should be
carefully examined for the presence of tumor. Although to date
there have been few reports on the use of CEUS in the diagnosis
of pediatric renal masses, this modality is potentially of great
usefulness (Fig. 52.64). CT and MRI are usually performed for
further workup and staging. 202
Mesoblastic Nephroma
Mesoblastic nephroma or fetal renal hamartoma is the most
common neonatal renal neoplasm, and is sometimes detected
in the fetus. It is a benign tumor but can spread through local
A
B
FIG. 52.62 Wilms Tumor. (A) Longitudinal gray-scale image depicts a large, hyperechoic mass (arrows) arising from the upper and middle
portions of the left kidney (K). Multiple anechoic zones within the tumor are the sequelae of hemorrhage and/or necrosis. (B) Longitudinal color
Doppler image depicts less blood low within the tumor than in the adjacent renal parenchyma.