Diagnostic ultrasound ( PDFDrive )

1344 PART IV Obstetric and Fetal Sonography
FIG. 39.7 Absent Renal Arteries. Color Doppler ultrasound shows
no renal artery arising from the aorta (Ao) in a fetus with bilateral renal
agenesis.
FIG. 39.9 Pelvic Kidney. Coronal image in a 23-week fetus shows
the ectopic kidney (calipers) adjacent to the iliac wing and bladder (B).
See also Video 39.3.
irst- and second-degree relatives of afected fetuses have been
found to have congenital renal anomalies, most oten unilateral
renal agenesis; and in these families the recurrence risk may be
higher. 34,36 Screening parents and siblings with renal ultrasound
is recommended. 34
FIG. 39.8 Normal Renal Arteries. Color Doppler ultrasound maps
out the renal arteries bilaterally (arrows) in a 19-week fetus, conirming
the presence of kidneys.
Bilateral Renal Agenesis
SONOGRAPHIC FINDINGS
Severe oligohydramnios
Absent kidneys
“Lying down” adrenal sign
Absent renal arteries on color Doppler imaging
Nonvisualization of bladder (over 1 hour)
TECHNICAL LIMITATIONS
Poor image quality caused by oligohydramnios
Fetal position (breech presentation)
PITFALLS IN INTERPRETATION
Amniotic luid volume may be normal before 16 weeks’
gestation
Bowel or adrenal glands can be mistaken for kidneys
Urachal diverticulum may mimic the bladder
Empty bladder may be caused by impaired renal function
from other causes (e.g., intrauterine growth restriction)
Unilateral Renal Agenesis
Unilateral renal agenesis is three to four times more common
than bilateral renal agenesis, occurring 1 in 1000 births. 3 It can
be diicult to diagnose prenatally because AFV is normal and
the bladder appears normal. A common pitfall is failure to image
the renal fossa in the far ield because of acoustic shadowing
from the spine, especially in the transverse plane. Meticulous
attention to technique is necessary (rotating the transducer,
changing the maternal position, or repeated observations). If a
kidney is not found in the renal fossa, most are either congenitally
absent or ectopic. 55,56 he contralateral kidney may be enlarged
because of compensatory hypertrophy. 57 here is a high incidence
of contralateral renal abnormalities, the most common being
vesicoureteral relux (VUR). 58 Unilateral renal agenesis is associated
with genital, cardiac, skeletal, and GI abnormalities, as well
as with multiorgan syndromes. 59 Isolated unilateral renal agenesis
has a good prognosis. Neonatal urologic workup is necessary,
including a voiding cystourethrogram (VCUG).
he recurrence risk to parents of a baby with isolated unilateral
renal agenesis is about 1% if the parents have normal renal
ultrasound. However, if one parent has a congenital solitary
kidney, the risks to ofspring are 7% for congenital solitary kidney
and 1% for bilateral renal agenesis. 60
Renal Ectopia
One or both kidneys may be in an abnormal position. he
incidence of renal ectopia varies between 1 : 500 and 1 : 1200
births, with pelvic kidney being the most common form. 61 When
the renal fossa is empty, careful scanning may demonstrate the
ectopic kidney adjacent to the bladder or iliac wing (Fig. 39.9,
Video 39.3). However, prenatal detection is oten diicult because