Diagnostic ultrasound ( PDFDrive )

CHAPTER 39 The Fetal Urogenital Tract 1355
Ultrasound grading system of hydronephrosis
Grade 0
Grade 1
Grade 2
Grade 3
Grade 4
FIG. 39.26 Society for Fetal Urology Grading System. This classiication
is based on the appearance of the renal pelvis, calyces, and
renal parenchyma. Grade 0: no hydronephrosis; intact central renal
complex. Grade 1: only dilated renal pelvis; there is some luid in the
renal pelvis. Grade 2: dilated renal pelvis and a few calyces are visible.
Grade 3: all the calyces are dilated. Grade 4: further dilation of renal
pelvis and calyces, with thin renal parenchyma. (Modiied from Baskin
LS. Prenatal hydronephrosis. In: Baskin LS, Kogan B, Duckett J, editors.
Handbook of pediatric urology. Philadelphia: Lippincott-Raven; 1997.
p. 15. 281 )
diferentiation, cortical cysts); (5) ureteral abnormalities; (6)
bladder abnormalities; and (7) oligohydramnios. 133
he classiication is based on the presence of the most concerning
feature. he proposed thresholds for normal RPD are less
than 4 mm at 16 to 27 weeks and less than 7 mm at 28 weeks or
more (Table 39.4).
he detection of UT dilation (pyelectasis) is important for
two reasons: aneuploidy and postnatal uropathy. he signiicance
of UT dilation as a marker for aneuploidy is discussed in Chapter
31. UT dilation is usually an isolated inding, but a detailed
ultrasound examination should be performed to detect other
UT pathologic processes and nonrenal anomalies. UT dilation
may be the irst manifestation of obstructive uropathy. Studies
that have correlated outcome with UT dilation varied widely in
methodology, using diferent RPD cut-ofs and diferent outcome
measures. In a meta-analysis of 17 studies (104,572 patients
screened), Lee and colleagues examined antenatal hydronephrosis
(1308 subjects) as a predictor of postnatal outcome. 149 he risk
of any postnatal pathology was 12% for mild, 45% for moderate,
and 88% for severe hydronephrosis (Table 39.5). here was a
signiicant increase in the risk of postnatal pathology with
increasing degree of hydronephrosis. A prospective study by
Sairam and colleagues 131 reported on the natural history of
hydronephrosis diagnosed in 227 fetuses on midtrimester
ultrasound in an unselected population. hey demonstrated that
96% of the fetuses with mild hydronephrosis (RPD > 4 mm and
< 7 mm at 18-23 weeks) experienced resolution in either the
third trimester or the early neonatal period; none required
postnatal surgery. However, approximately one in three fetuses
with moderate to severe hydronephrosis (RPD > 7 mm or presence
of caliectasis at 18-23 weeks) required postnatal surgery. A
meta-analysis by Sidhu and colleagues combined data from seven
studies and reported on the indings of serial postnatal renal
sonography in children with isolated antenatal hydronephrosis. 150
here was resolution, improvement, or stabilization of hydronephrosis
in 98% of patients with SFU grades 1 and 2 and stabilization
of hydronephrosis in 51% of those with SFU grades 3 and
4. hese results suggest that mild hydronephrosis is a relatively
benign condition.
In utero progression also increases the likelihood of postnatal
uropathy and urologic surgery. 141,151-153 An abnormal RPD in the
third trimester is the best ultrasound criterion to predict postnatal
uropathy. 128,141 In cases of mild isolated UT dilation, serial
follow-up scans every 3 to 4 weeks are not necessary, but a repeat
ultrasound in the third trimester is recommended. As prenatal
resolution has been shown to be frequent, 131,142 this will also
identify a group in which postnatal follow-up may not even be
necessary. 133 In general, the larger the RPD, the lower the spontaneous
resolution rate, the more likely it is associated with
postnatal pathology, and the greater the need for postnatal
surgery. 131,150,154-156
A risk stratiication of prenatal UT dilation into a low-risk
group and an increased-risk group has been proposed. 133 Fetuses
with isolated mild UT dilation are classiied in the low-risk group
(Fig. 39.27) if the RPD is 4 to less than 7 mm at less than 28
weeks, and 7 to less than 10 mm at 28 weeks or more. Fetuses
with greater degrees of UT dilation (RPD ≥ 7 mm at <28 weeks
and ≥ 10 mm at ≥28 weeks) or any one of several indings—
peripheral calyceal dilation, abnormal renal parenchymal thickness
or appearance, dilated ureter, abnormal bladder, or
oligohydramnios—are considered at increased risk for postnatal
uropathy (Fig. 39.28).
he majority of infants identiied prenatally as having UT
dilation are asymptomatic at birth. Pediatric nephrologists
and urologists vary greatly in their management of antenatally
diagnosed UT dilation, because an evidence-based protocol