Diagnostic ultrasound ( PDFDrive )

CHAPTER 39 The Fetal Urogenital Tract 1343
FIG. 39.5 “Lying Down” Adrenal Sign. Longitudinal scan through
the renal fossa shows absence of the kidney and the lattened adrenal
gland (arrows). The lying-down adrenal sign is an indication of renal
agenesis or ectopia. See also Video 39.1.
absent renal arteries, providing further evidence for the diagnosis
of bilateral renal agenesis (Fig. 39.7). More important, it helps
to map out the renal arteries in diicult cases of oligohydramnios,
thereby conirming the presence of kidneys and avoiding confusion
(Fig. 39.8).
Fetal MRI may help to identify the kidneys when sonographic
visualization is limited. However, the kidneys can be diicult to
visualize early in gestation. herefore it may be diicult for MRI
to exclude renal agenesis before 24 weeks’ gestation, if the kidneys
are not seen.
Bilateral renal agenesis is usually an isolated and sporadic
abnormality. However, in a small percentage of cases it may be
secondary to a chromosomal abnormality or part of a genetic
syndrome (such as Fraser syndrome), or a developmental defect
(such as VACTERL association). 51,52 here is conlicting evidence
with regard to associations between bilateral renal agenesis and
maternal factors such as prepregnancy obesity, periconception
smoking, and alcohol consumption. 53 In nonsyndromic cases,
the recurrence risk of having another child with bilateral renal
agenesis is approximately 4%. 34,54 However, up to 15% of the
A
B
C
FIG. 39.6 Bilateral Renal Agenesis. (A) Color Doppler
image of the umbilical arteries (arrows) in a 20-week fetus
with breech presentation shows nonvisualization of the
bladder during 1 hour of observation. Note severe oligohydramnios.
(B) Transvaginal ultrasound shows prominent
adrenal glands (arrows) in the renal fossa and no kidneys.
(C) Postmortem photograph shows lattened, discoid-shaped
adrenal glands in both renal fossa, with absent kidneys. See
also Video 39.2. (C courtesy of Patrick Shannon, MD, Department
of Pathology and Laboratory Medicine, Mount Sinai
Hospital, Toronto.)