Diagnostic ultrasound ( PDFDrive )

1354 PART IV Obstetric and Fetal Sonography
more likely to regress, whereas those with an echogenic appearance
are more likely to grow. 116 he adrenal gland is not identiied on
the ipsilateral side. Most reported cases of neuroblastoma have
been identiied in the third trimester. Metastases (liver, placenta)
and hydrops are rare but have been reported. 119,120 Fetal hypertension
with secondary cardiomyopathy diagnosed on fetal
echocardiography has also been reported, due to either elevation
in circulating catecholamines produced by the tumor versus
compression of the renal artery by the bulk of the tumor causing
renovascular hypertension. 121 MRI may be useful for detailed
anatomic characterization of the tumor and extent of disease. 116
Associated fetal anomalies have been reported, particularly cardiac
defects, in addition to certain syndromes. 120 here may be maternal
symptoms of hypertension, tachycardia, or preeclampsia, which
result from elevated catecholamines and correlate with a more
advanced stage of disease. 122
Prenatally detected neuroblastomas generally have a favorable
outcome, and surgical resection is usually curative. 120,123 A recent
prospective study evaluating expectant observation versus surgical
management conirmed the safety and efectiveness of expectant
observation as a primary management strategy in infants younger
than 6 months with small adrenal masses (solid tumors < 3.1 cm
or cystic tumors < 5 cm with at least 25% cystic component)
that were shown to be stage 1 according to the International
Neuroblastoma Staging System. 124 his approach allows for
avoidance of surgery in a large majority of infants whose tumors
regress spontaneously. 124
Adrenal hemorrhage, which is much more common in the
neonate than in the fetus, can have a prenatal sonographic
appearance similar to that of an adrenal or renal neoplasm. Color
Doppler shows no low within the mass and may be helpful in
diferentiation. 125 he key to the diagnosis of adrenal hemorrhage
is evolution of the lesion over time; serial sonograms demonstrate
a change in echogenicity (from solid appearing to cystic) and a
decrease in size of the mass. 126,127 However, because neuroblastomas
may also regress, it is important to obtain postnatal
follow-up in fetuses with presumed adrenal hemorrhage.
Upper Urinary Tract Dilation
Dilation of the upper UT accounts for approximately 50% of all
prenatally detected renal abnormalities. 128 It may be unilateral
or bilateral and is more common in males than females. 129 Prospective
studies in unselected populations have reported a prevalence
of 0.7% to 3.9% in the second trimester. 129-131 In the majority of
cases (50%-70%), the UT dilation is transient or physiologic
and has no clinical signiicance. 132,133 In other cases, the dilation
is due to an obstructive or nonobstructive etiology, including
ureteropelvic junction obstruction (10%-30%), vesicoureteral
relux (10%-40%), ureterovesical junction obstruction/
megureter (5%-15%), posterior urethral valves (1%-5%), and
uncommon causes (duplex system, ectopic ureter, ureterocele,
urethral atresia). 133
“Hydronephrosis” refers to abnormal dilation of the renal
pelvis and calyces. he term “pyelectasis” implies a milder
form of hydronephrosis, with dilation of the renal pelvis only.
Measurement of the anteroposterior renal pelvic diameter
(RPD) is the simplest and the most common technique used to
FIG. 39.25 Measurement of Anterior-Posterior Renal Pelvic
Diameter (RPD). Transverse scan of the abdomen in a 22-week fetus,
obtained with the fetus in a prone position, shows dilated renal pelvis
bilaterally. The calipers are placed at the widest part of the intrarenal
luid.
evaluate renal pelvic dilation. For optimal technique, a transverse
image of the kidneys is obtained with the spine at the 12 or 6
o’clock position, and the measurement should be taken at the
maximal diameter of the intrarenal pelvis (Fig. 39.25). he size
of the renal pelvis increases throughout gestation, and there are
published nomograms for RPD. 6,134,135 Controversy surrounds
the deinition and clinical importance of mild renal pelvic
dilation, and diferent threshold values of RPD have been used
for the antenatal diagnosis of renal pelvic dilation. In general,
the cutof values for RPD vary between 4 mm and 5 mm in
the second trimester and between 7 and 10 mm in the third
trimester. 130,131,136-142 Although using a cutof value of 4 mm in
midgestation can increase the sensitivity for the detection of
renal pathology, it is important to realize that it can lead to a
high false-positive rate, perhaps generating unnecessary parental
anxiety. 143 Factors such as maternal hydration status, maternal
pyelectasis, and size of the fetal bladder may afect the RPD
measurement. 144-147 hese indings suggest caution when considering
the implications of renal pelvic dilation based on a single RPD
measurement. Calyceal dilation is an important inding and is
always pathologic, independent of the pelvic size. 131,143 he Society
for Fetal Urology (SFU) proposed a classiication system in 1993,
based on the degree of renal pelvic dilation (mild, moderate,
marked), while also including parameters of calyceal dilation and
the appearance of the renal parenchyma. 132,148 he classiication
system consists of ive grades: grade 0 representing no dilation,
and grades 1 to 4 representing dilation of increasing severity
(Fig. 39.26).
A consensus conference in March 2014 proposed a standardized
classiication system for UT dilation based on seven
ultrasound parameters: (1) anteroposterior RPD; (2) calyceal
dilation—central (major calyces) or peripheral (minor calyces);
(3) renal parenchymal thickness (subjective assessment); (4)
renal parenchymal appearance (echogenicity, corticomedullary