ultrasound diagnosis of fatal anomalies

UROGENITAL TRACT
Fig. 7.34 Urethral valve sequence. The same fetus
after birth at 29 weeks of gestation.
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5
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cryptorchidism) is a distinct entity or forms part
of the urethral valve sequence.
Ultrasound findings: These show signs of obstruction
in the lower urinary tract: distension of
the urinary bladder with thickening of the bladder
wall and “keyhole” phenomenon, with dilation
of the renal pelvis and the ureter, along with
oligohydramnios or anhydramnios. Complications
such as ascites secondary to rupture of the
distended bladder, causing abdominal distension,
may occur.
Caution: An extremely full bladder may be incorrectly
interpreted as urethral obstruction. However,
in this case the amniotic fluid index is normal
and other signs of obstruction are not found.
Clinical management: Karyotyping; further
sonographic screening, including fetal echocardiography.
Consultation with a pediatric urologist
to discuss the findings in the prenatal stage
and to counsel the parents. Early delivery is an
option after 32 weeks. Prior to this, puncture of
the fetal urinary bladder and examination of the
urine is helpful to obtain a rough estimate of
renal function. Repeated puncture or insertion of
a catheter to facilitate drainage may be required.
Fetal therapy using laser is still at the experimental
stage. Repeated instillation of fluid into
the amniotic cavity may be considered, to prevent
hypoplasia of the lungs resulting from
anhydramnios.
Procedure after birth: If the anhydramnios has
been present over a long period, hypoplasia of
the lungs can be expected. Drainage of the urine
is achieved by vesicotomy or ureterostomy.
Renal function often recovers only gradually.
Transurethral resection of the valve using endoscopic
techniques is also a therapeutic option.
Renal insufficiency and urinary incontinence
may also develop.
Prognosis: This depends on the severity of renal
function disturbance. The overall mortality is
50%; in the presence of oligo-anhydramnios it
increases to 95%. Spontaneous recovery of the
lesion in the prenatal stage has also been known
to occur in 50% of cases if the diagnosis is made
early.
References
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