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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5514_Библиотеки_им_академика_М_И_Перельмана.pdf
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E. R. Oliver and S. J. Back
Prenatal Imaging Findings
Bladder Exstrophy
Demonstration of a uid-lled urinary bladder is a required component of all fetal
anatomic examinations, regardless of whether the examination is a routine secondtrimester screening ultrasound, a detailed fetal anatomic survey performed for a
known or suspected anomaly, or a late rst-trimester anatomic survey for patients in
whom earlier assessment is indicated [1–3]. The normal fetal urinary bladder is
located in the midline anterior pelvis, is bordered on both sides by the umbilical
arteries (Fig.4.1), and should ll and empty over the course of an examination. In
the case of bladder exstrophy, the anterior abdominal wall and bladder fail to fuse
and result in an infraumbilical wall defect with bladder mucosa exposed to the
amniotic uid. Fetal urine is released directly into amniotic space, leading to the
pathognomonic nding of bladder exstrophy—a non-visualized, or “absent,” urinary bladder (Figs.4.2 and 4.3) [4, 5].
In addition to an “absent” urinary bladder, several other sonographic ndings are
typically present that assist in prenatally diagnosing bladder exstrophy. These
include a low abdominal cord insertion (Figs.4.2 and 4.3); genital abnormalities
(Fig.4.4), such as epispadias or bid penis in males and bid clitoris and vaginal
and/or uterine anomalies in females; and bony pelvic abnormalities, such as pubic
diastasis and attening of the iliac bones (Figs.4.2 and 4.3) [4–7]. The exstrophied
bladder may vary in appearance and range from irregularity of the infraumbilical
abdominal wall (Fig.4.4) to a bulging infraumbilical mass mimicking an omphalocele (Fig.4.5) [4, 8]. In the former instance, the infraumbilical irregularity is secondary to inammation of the exposed posterior bladder wall mucosa, whereas in
the latter instance, the mass-like appearance is secondary to protrusion and eversion
of the bladder plate.
MRI is a powerful imaging adjunct for the assessment of complex fetal anomalies, and, unlike ultrasound, is not subject to some of the limitations that can constrain sonographic evaluation, such as fetal positioning, anterior placenta, and
maternal body habitus [9]. In addition, MRI offers excellent tissue contrast, which
is particularly helpful in evaluating genitourinary and gastrointestinal
abnormalities.
The primary MRI ndings of isolated bladder exstrophy are identical to those of
ultrasound—non-visualized urinary bladder, infraumbilical abdominal wall defect
with a low cord insertion, and pubic diastasis (Figs.4.6, 4.7, and 4.8)—however, the
added value of MRI is in conrming the absence of other anomalies that may confer
a more severe diagnosis on the EEC spectrum. The T1-signal characteristics of
meconium allow for thorough assessment for hindgut abnormalities, which should
be absent in isolated bladder exstrophy. T1-hyperintense meconium should be seen
4 Prenatal and Postnatal Imaging of the Bladder Epispadias-Exstrophy Complex
35
a
b
c
Fig. 4.1 Normal ultrasound ndings in a 21-week gestation fetus (a) and a 22-week gestation
fetus (b and c). (a) Color Doppler image through the pelvis demonstrates a normal anechoic and
uid-lled bladder bordered by both umbilical arteries. (b) Transverse grayscale image through
the iliac wings demonstrates a normal iliac angle. (c) A transverse grayscale image through the
lower pelvis shows a normal conguration of the symphysis pubis with the ossication centers
(arrows) appropriately angled toward the midline. Distance between the ossied portions of the
symphysis pubis measured <1cm (not shown)
within the rectum after 20weeks gestational age, and there should be progressive
lling of the more proximal colon as the pregnancy advances [10]. If an anteriorly
displaced anus is present, the course of the rectum to the perineum may be easier to
appreciate on MRI, as the rectal meconium signal should be readily identiable
(Figs.4.6, 4.7, and 4.8).
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E. R. Oliver and S. J. Back
Fig. 4.2
Ultrasound ndings of classic bladder exstrophy at 21weeks gestation. (a) Transverse
color Doppler image through the pelvis and umbilical arteries demonstrates the absence of an
anechoic uid-lled bladder between the two umbilical arteries, consistent with bladder exstrophy.
(b) Sagittal grayscale image through the lower abdomen demonstrates an infraumbilical defect
(arrowhead) representing the exstrophied bladder immediately below the abdominal cord insertion
(arrow) and cephalad to the external genitalia (open arrowhead), which were abnormal in appearance (not shown). (c) Transverse grayscale image through the pelvis demonstrates the infraumbilical defect (arrowheads) and bladder plate bulging between the exed and adducted legs. (d)
Transverse grayscale image through the anterior bony pelvis reveals separation of the symphysis
pubis (arrows) with the ossied portions demonstrating an abnormal parallel conguration. In
addition, the distance between the ossied portions of the symphysis is abnormal and >1 cm
(1.3cm, not shown), and the ndings are consistent with pubic diastasis. (e) Transverse grayscale
image through the perineum reveals normal hyperechoic anal mucosa (*) surrounded by a ring of
normal hypoechoic anal sphincter muscle (open arrows). (f) Sagittal grayscale image through the
pelvis and perineum reveals the normal echogenic rectal mucosa (*) extending to the anal orice
(open arrow). (g) Postnatal photograph demonstrating the exstrophied bladder (between open
arrows) and the abnormal external male genitalia consistent with epispadias (circle)
4 Prenatal and Postnatal Imaging of the Bladder Epispadias-Exstrophy Complex
37
e
f
g
Fig. 4.2 (continued)
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E. R. Oliver and S. J. Back
Careful assessment of the abdomen and pelvis is crucial in distinguishing isolated bladder exstrophy from bladder exstrophy associated with cloacal exstrophy,
which is discussed in greater detail in the following section. In isolated bladder
exstrophy, there should be no abnormalities of the spine, such as spinal dysraphisms
or anomalous vertebrae. Similarly, abnormalities of the hindgut, such as imperforate
anus, should not be present in isolated bladder exstrophy. It is important to note that
the anus may be anteriorly displaced in isolated bladder exstrophy and slightly difcult to demonstrate, potentially giving the false impression of an associated imperforate anus. Careful assessment of the perineum can often identify a displaced anus
and avoid misdiagnosis. Free-oating intra-amniotic bowel loops also should not be
seen in cases of isolated bladder exstrophy, as fusion of the posterior bladder plate
halves prevents extrusion of bowel loops into the amniotic uid; identication of
intra-amniotic bowel loops arising through an infraumbilical defect strongly suggests that the bladder halves are separate and unfused, which is a feature of cloacal
exstrophy. Lastly, the abdominal wall defect present in isolated bladder exstrophy
should be infraumbilical and not involve or extend above the level of the cord insertion, as would be seen with an omphalocele.
Fig. 4.3
Ultrasound ndings of classic bladder exstrophy at 24weeks gestation. (a) Transverse
color Doppler image through the pelvis and umbilical arteries demonstrates the absence of an
anechoic uid-lled bladder between the two umbilical arteries. (b) Sagittal grayscale image
through the lower abdomen demonstrates an infraumbilical defect (arrowhead) representing the
exstrophied bladder immediately below the abdominal cord insertion (arrow) and cephalad to the
external genitalia (open arrow). (c) Three-dimensional image of the lower abdominal and pelvic
wall shows the abdominal cord insertion (arrow), the bladder plate (arrowhead) bulging between
the exed and adducted legs, and the external genitalia (open arrowhead). (d) Transverse grayscale
image through the anterior bony pelvis demonstrates pubic diastasis (arrows). Although one ossication center is angled toward the midline, the other is not, and the distance between the ossied
portions is abnormal and >1cm (1.6cm, not shown). (e) Transverse grayscale image through the
bony pelvis at the level of the lumbosacral junction reveals posterior rotation of the iliac bones,
resulting in an abnormally increased iliac wing angle
4 Prenatal and Postnatal Imaging of the Bladder Epispadias-Exstrophy Complex
ba
dc
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e
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E. R. Oliver and S. J. Back
Fig. 4.4 US ndings of the abnormal external genitalia and irregular bladder mucosa in classic
bladder exstrophy at 19weeks gestation. (a) Transverse grayscale image of the external genitalia
reveals an abnormal ambiguous appearance of the genitalia (circle). (b) Sagittal grayscale image
through the lower abdomen demonstrates a ventral wall defect between the abdominal cord insertion (ACI) and external genitalia (closed arrows). The defect has a lobulated and irregular surface
(open arrows). (c) Transverse grayscale image of the infraumbilical defect further illustrates the
irregular contour of the defect (open arrows), corresponding to the inamed bladder mucosa. (d)
Postnatal photograph reveals the lobulated exposed bladder mucosa (between open arrows) and
abnormal male external genitalia with epispadias (circle)
ab
4 Prenatal and Postnatal Imaging of the Bladder Epispadias-Exstrophy Complex
Fig. 4.5 Classic bladder exstrophy with ultrasound ndings mimicking a bowel-containing
omphalocele at 27weeks gestation. (a) Transverse grayscale image of the abdomen demonstrates
a protruding ventral wall defect containing non-dilated bowel (arrowheads). (b) Sagittal grayscale
image reveals that the ventral wall defect (arrowheads) is infraumbilical and immediately below
the ACI (arrow) and cephalad to the external genitalia (open arrowhead). The infraumbilical location and absence of a uid-lled bladder on other images (not shown) are consistent with bladder
exstrophy with a protruding bladder plate rather than an omphalocele
41
Cloacal Exstrophy
Cloacal exstrophy represents a more severe constellation of urogenital and gastrointestinal malformations and is considered by many to represent the most severe clinical entity on the bladder exstrophy-epispadias complex spectrum [11, 12]. In
addition to bladder exstrophy, an omphalocele, imperforate anus, and spine abnormality are classically present, leading to the acronym by which this entity is also
known—omphalocele, bladder exstrophy, imperforate anus, and spine anomalies
(OEIS) complex. The acronym OEIS was originally coined as a mnemonic for the
typical anomalies seen in cloacal exstrophy [13], and the terms “cloacal exstrophy”
and “OEIS complex” should be considered synonymous [14]. It is also important to
recognize that not all four components of classic cloacal exstrophy need to be present for its diagnosis [15]. Indeed, in one series of cloacal exstrophy, only 22.6% had
all four components (OEIS), 32.8% had cloacal exstrophy without spine abnormalities (OIE), and 18% had cloacal exstrophy without omphalocele (EIS) [15].
Therefore, when making a prenatal diagnosis of cloacal exstrophy, it is likely best
to specify which individual components are present (e.g., “Cloacal exstrophy, characterized by …”), as this will help optimize prenatal counseling, delivery planning,
and neonatal management [16].
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E. R. Oliver and S. J. Back
Fig. 4.6 MRI ndings of classic bladder exstrophy at 22weeks gestation. (a) Transverse FSE
T2-weighted image (TR/TE ms, 1100/84) through the lower abdomen just below the level of the
umbilical cord insertion demonstrates the absence of a uid-lled bladder and a relatively small
infraumbilical defect (arrowheads). (b) Sagittal SSFP image (TR/TE ms, 3.99/1.74) through the
mid-abdomen demonstrates a ventral wall defect (arrowhead) located immediately below the level
of a low ACI (black arrowhead) representing the exstrophied bladder. *, umbilical cord. (c)
Transverse EPI image (TR/TE ms, 5841/50) through the lower bony pelvis demonstrates widening
of the symphysis pubis (measured distance 1.2cm). (d) Sagittal T1-weighted gradient echo image
(TR/TE ms, 202/4.76) through the lower abdomen and pelvis demonstrates a normal course of the
T1-hyperintense meconium (arrows) extending to the perineum, arguing against the presence of an
imperforate anus/anorectal malformation. A uid-lled bladder was not identied on any other
sequences, and the constellation of ndings is consistent with classic bladder exstrophy
4 Prenatal and Postnatal Imaging of the Bladder Epispadias-Exstrophy Complex
43
a
b
c
Fig. 4.7 MRI ndings of classic bladder exstrophy at 21weeks gestation (same case as Fig. 4.2).
(a) Transverse FSE T2-weighted image (TR/TE ms, 1100/76) through the lower abdomen just
below the level of the umbilical cord insertion demonstrates the absence of a uid-lled bladder
and a relatively small infraumbilical defect (arrowheads) protruding between the adducted legs. (b)
Sagittal SSFP image (TR/TE ms, 4.18/1.92) through the mid-abdomen demonstrates a ventral wall
defect (arrowhead) that was immediately below the level of the ACI (not shown) representing the
exstrophied bladder and cephalad to the external genitalia (open arrowhead). (c) Sagittal
T1-weighted gradient echo image (TR/TE ms, 209/4.76) through the lower abdomen and pelvis
demonstrates a normal course of the T1-hyperintense meconium (arrows) extending to the
perineum, which argues against imperforate anus/anorectal malformation. A uid-lled bladder
was not identied on any other sequences, and the ndings are consistent with classic bladder
exstrophy