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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5759_Библиотеки_им_академика_М_И_Перельмана
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Chapter 44 ■ Sonographic Evaluation of the Placenta 1507
FIGURE 44-11. Placenta accreta. Coronal T2-weighted
MR image shows an absent myometrial-placental interface in a
posterolateral location (arrow) surrounded by normal myometrial-
placental interface in a patient with previous posterior myomectomy. This region was not well evaluated with ultrasound. (From
Levine D. Placenta accreta: evaluation with color Doppler, power
Doppler and fast MRI. Radiology 1997;205:773.)
PL
FIGURE 44-12. Placental abruption. Transabdominal
sonogram of the placenta (PL) with a hematoma (calipers) lifting
the placenta away from the uterine wall.
BA
FIGURE 44-13. Subchorionic hematoma. A, Transabdominal transverse view of the uterus in the second trimester shows acute
subchorionic hematoma (calipers). The anterior placenta is shown by the short arrow. B, Transabdominal midsagittal view of the same
patient later in pregnancy demonstrates the subchorionic hematoma (long arrow) more hypoechoic and located overlying the cervix (cali-
pers); short arrow, placenta.
1508 PART IV ■ Obstetric Sonography
A B
FIGURE 44-14. Preplacental hematoma. A and B, Transabdominal sonograms early in the third trimester demonstrate a hema-
toma on the fetal side of the placenta (arrow). The fetus had severe growth restriction and died within 2 days of the ultrasound
examination.
FIGURE 44-15. Large hematoma. Transabdominal sono-
gram shows large hematoma (H, calipers). The placenta (*) is
anterior.
by bleeding from fetal vessels and located on the fetal
surface of the placenta under the chorion (Fig. 44-14).
Because preplacental hematomas likely result from the
accumulation of fetal blood, prognosis may be poorer.
80
When massive, these hematomas are sometimes termed
Breus mole. Preplacental hematomas may be associated
with maternal hypertension.
81
An acute hematoma has an echogenicity similar to
that of the placenta, making sonographic visualization
difficult. As the hematoma organizes, it becomes more
hypoechoic (Fig. 44-13, B) and can approach the
*
X
H
X
X
echogenicity of the myometrium. An indirect sign of the
presence of a hematoma is apparent thickening of the
placenta, which is associated with worse outcomes.
Even though placental abruption remains a clinical
diagnosis, ultrasound can play an important role. Larger
hematomas are expected to be seen (Fig. 44-15), and
these are more likely to be clinically important. Glantz
and Purnell
84
reported that the identification of placental abruption by ultrasound had a sensitivity, specificity,
positive predictive value, and negative predictive value
of 24%, 96%, 88%, and 53%, respectively. They
X
82,83
Chapter 44 ■ Sonographic Evaluation of the Placenta 1509
A
C
determined that if a hematoma was identified by sonography, there was an increased risk of preterm delivery,
low birth weight, and neonatal intensive care unit
admission. Increased size of hematoma and percentage
of placental involvement are associated with increased
fetal mortality.
85
PLACENTAL INFARCTION
Placental infarctions can occur focally or throughout the
placenta and are thought to have a vascular etiology.
Maternal floor infarction is a diffuse entity overtaking
the villi with a fibrinoid deposition at the maternal
surface and basal plate, reaching into the placental substance. The presence of this fibrin surrounding the villi
obstructs nutrient exchange from mother to fetus. Both
abnormalities are associated with oligohydramnios,
umbilical artery Doppler abnormalities, IUGR, central
nervous system injury, and fetal demise. Maternal floor
infarction tends to recur in subsequent pregnancies.
24,86-88
B
FIGURE 44-16. Maternal floor infarction. A, Trans-
abdominal sonogram of a third-trimester placenta shows an echogenic mass (arrow) emanating from the basal plate into the
placenta. B, In another patient, color Doppler sonogram late in
the second trimester demonstrates a placental subchorionic cyst
(arrow). C, In another patient, highly echogenic basal plate
(arrows) suggests basal plate infarction.
Although peripheral infarctions are common at term,
infarctions larger than 3 cm or involving more than 5%
of the placenta are associated with increased perinatal
morbidity. Both maternal and fetal thrombophilias can
lead to placental infarctions.
89
The sonographic findings of maternal floor infarction
include a hyperechoic placental mass (Fig. 44-16, A) or
placental thickening. Hyperechoic areas of the placenta
are especially prominent along the maternal surface of
the placenta and can stretch into the placental substance
itself. These can be a normal finding, especially with
mature placentas. Hyperechoic placental masses may be
associated with central hypoechoic spaces as they organize. Subchorionic cysts are also commonly present
with maternal floor infarction (Fig. 44-16, B). The
hyperechoic mass seen with maternal floor infarction
resembles that seen with placental chorioangiomas.
Placental infarctions caused by maternal vascular
disease often result in uteroplacental ischemia and infarction of the villi. These appear as echogenic, rimmed
cystic lesions within the placenta, not necessarily at the
90
1510 PART IV ■ Obstetric Sonography
FIGURE 44-17. Placental infarctions in patient
with severe preeclampsia. Transabdominal sonogram of
a third-trimester placenta demonstrates multiple hyperechoic bordered cysts with sonolucent cores.
1
2
A B
FIGURE 44-18. Placental cysts. A, Transabdominal sonogram of a third-trimester placenta demonstrates a small placental cyst. B,
Transabdominal sonogram of a second-trimester placenta with a surface cyst (calipers) located near the umbilical cord insertion.
maternal side of the placenta or basal plate (Fig. 44-17;
Video 44-4
coagulation with heparin may improve outcome.
). When identified early in gestation, anti-
91
contain these cysts have normal outcomes. Larger cysts
4.5 cm) are associated with IUGR. Maternal floor
(>
infarction may also be associated with placental cysts.
92,93
The most common benign tumor of the placenta is
the chorioangioma, occurring in approximately 1% of
PLACENTAL MASSES
Solid-appearing placental masses include chorioangioma,
subamniotic hematoma, subchorionic hematoma,
and placental hemorrhage. These masses should be differentiated from fluid-filled placental regions of placental
cysts and venous lakes. As just discussed, placental infarctions may also have a masslike appearance.
Subchorionic placental cysts on the fetal surface of
the placenta are predominantly innocuous findings on
prenatal sonography, similar to cysts in the substance of
the placenta (Fig. 44-18). Most fetuses whose placentas
pregnancies (Fig. 44-19). Although most are asymptomatic, large chorioangiomas can lead to high-output fetal
cardiac failure, anemia, hydrops, and death.
94
Chorioangiomas appear as well-circumscribed solid tumors in the
placenta. They can range from hypoechoic to hyper echoic
compared to the echogenicity of the placenta. A threshold
of 5 cm in diameter typically portends a high risk for
adverse outcome.
95,96
Use of color or power Doppler
ultrasound is helpful to identify increased blood flow
within the solid mass, thereby distinguishing the mass as
a chorioangioma.
97,98
Blood flow is not consistently
demonstrable, especially with smaller chorioangiomas;
Chapter 44 ■ Sonographic Evaluation of the Placenta 1511
2
1
A
1 D 6.79cm
B C
1
1 D 6.03cm
2 D 5.14cm
D
E F G
FIGURE 44-19. Chorioangioma. A, Transabdominal sonogram shows a heterogeneous placental mass (calipers). B, In another
patient, transabdominal sonogram of a more homogeneous and isoechoic placental mass (calipers). C, In a different patient, transabdominal
color Doppler sonogram shows blood flow within the tumor. D, Same patient as C; 3-D color Doppler sonography demonstrates feeding
vessel (long arrow) and vasculature (short arrow) in the placental tumor. E and F, Gray-scale and color Doppler sonograms show another
patient with a small, hypovascular chorioangioma. G, Specimen.
1512 PART IV ■ Obstetric Sonography
those with low flow tend to have a better outcome,
whereas chorioangiomas with extremely elevated flow
usually are associated with adverse perinatal outcome.
These pregnancies require close follow-up and surveillance for polyhydramnios and other signs of fetal
hydrops.
color or power Doppler ultrasound, signals an improved
prognosis.
assist with the diagnosis of chorioangioma and can be
used to quantitate blood flow to the tumor.
99,100
Decreasing blood flow, as documented by
100
Three-dimensional power Doppler can
95
In cases where the fetus is at risk for hydrops, in
utero intervention improves perinatal outcomes. Interventions include injection of thrombogenic material,
microcoil embolization,
devascularization.
103
102
and endoscopic laser
101
Maternal malignancies rarely metastasize to the placenta. Malignant melanoma and adenocarcinoma of
the breast, pancreas, and colon are most common.
104,105
These deposits are typically microscopic and do not
interfere with placental function.
MESENCHYMAL DYSPLASIA
OF THE PLACENTA
Mesenchymal dysplasia of the placenta resembles a
partial hydatidiform mole both grossly and microscopically, with a thickened placenta and small cystic lesions.
In contrast to partial moles, mesenchymal dysplasia of
the placenta may be associated with a normal fetus,
although IUGR is common. There is also an association
with Beckwith-Wiedemann syndrome
The villi in these cases are cystic with dilated vasculature.
The karyotype is usually normal.
107
106
(Fig. 44-20).
MOLAR GESTATIONS
Gestational trophoblastic disease consists of complete
mole (Fig. 44-21) and partial mole and choriocarcinoma. These placental abnormalities are discussed in
detail in Chapter 15.
FIGURE 44-20. Mesenchymal dysplasia of pla-
centa. Associated with Beckwith-Weidemann syndrome at 20
weeks’ gestation. Note the enlarged placenta (8 cm, calipers) with
multiple cystic spaces.
FIGURE 44-21. Molar pregnancy. Transvaginal sonogram
in the late first trimester demonstrates a moderate amount of
gestational tissue with multiple cystic spaces.
1
2
Chapter 44 ■ Sonographic Evaluation of the Placenta 1513
MORPHOLOGIC PLACENTAL
ABNORMALITIES
There are a number of placental shape abnormalities,
some quite rare.
Circumvallate Placenta
In circumvallate placenta the membranes of the chorion
laeve, instead of inserting at the margin of the placental
disc, insert more toward the center of the disc. The
pathologist can identify fibrin at the margin along with
evidence of bleeding. With a complete circumvallate placenta, a ring may constrict the chorion frondosum.
24
Because of this placement, there is disproportionate
folding of the placenta and fetal membranes. This results
in the chorionic plate being smaller than the basal plate.
Within the membrane fold hyalinized villi may be seen
after being incorporated into the fold.
Circumvallate placenta has the sonographic appearance of a rolled edge of membranes at the placental edge
inserting toward the center of the placental chorionic
disc (Fig. 44-22; Video 44-5). Termed a placental shelf,
this rolled edge of membranes can be thick and most
often occupies only a small portion of the placenta.
Circumvallate placentas can also be confused with
uterine synechiae (Fig. 44-23, A), uterine septum (Fig.
44-23, B), and amniotic bands. Carefully identifying
A B
FIGURE 44-22. Circumvallate placenta. A, Transabdominal sonogram in the early third trimester shows rolled edges of the
placenta (arrows). B, Transabdominal sonogram in the second trimester shows a placental shelf (arrow), which has echogenicity similar to
the remainder of the placenta.
A B
FIGURE 44-23. Mimics of circumvallate placenta. A, Placenta abutting a uterine synechia (long arrow) of myometrial tissue;
short arrow, placental edge. B, Transabdominal sonogram of a second-trimester pregnancy with a uterine septum (arrow). The placenta
partially inserts on the uterine septum.
1514 PART IV ■ Obstetric Sonography
the insertion of the membranes and determination of the
echogenicity of the rolled edge of placenta, which should
be similar to that of the placenta, should provide the
correct diagnosis.
If a circumvallate placenta is identified, even if it
seems to occupy only a small portion of the placenta, the
rest of the placenta must be evaluated to determine
whether the rolled edge of membranes involves the entire
placenta. Complete circumvallate placentae are associated with adverse neonatal outcomes, including placental
abruption, preterm delivery, oligohydramnios, IUGR,
emergency cesarean delivery, Apgar scores less than 7,
and perinatal death.
108,109
Fortunately, complete circumvallate placenta is rare, whereas partial circumvallate placentas are quite common and should be regarded as
normal variants.
Evaluating second-trimester placental shelves to determine whether the sonographic finding persisted into the
third trimester, Shen et al.
108
found an incidence of 11%
for the identification of these shelves at the 13 to 16–week
scan. Of note, none of the placental shelves occupied
more than 25% of the placenta. Also, none of the partial
circumvallate placentas could be sonographically appreciated in the third trimester. All neonates had a normal
outcome. A recent large study of postdelivery placenta
inspection yielded a complete circumvallate placenta incidence of 1.8%, none of which was detected antenatally.
Succenturiate Lobe
Succenturiate lobes, or accessory lobes, of the placenta
can be a single lobe or multiple lobes in addition to the
main placental lobe (Fig. 44-24). Their incidence is as
high as 6%.
24
Given that placental tissue is present in
the accessory lobe, there must be arterial and venous
connections to the main portion of the placenta. One
concern involves a retained placental accessory lobe after
delivery, if not expected from the antenatal sonogram.
A
C
B
FIGURE 44-24. Succenturiate lobe. A, Transabdominal
sonogram of a third-trimester pregnancy shows a portion of placenta
(arrow) separate from the main placental disc. B, Transvaginal
sonogram of a third-trimester succenturiate lobe (arrow) that
overlies the cervix (calipers). C, In a different patient, transabdominal color and pulsed wave Doppler ultrasound demonstrate the
vascular connection between the succenturiate lobe and the main
placental disc.
Chapter 44 ■ Sonographic Evaluation of the Placenta 1515
A B
FIGURE 44-25. Bilobed placenta. A, Transabdominal sonogram of a third-trimester bilobed placenta. Both placental discs are of
comparable size (arrows). B, Pulsed wave Doppler ultrasound demonstrates a fetal vascular connection between the lobes. The umbilical
cord insertion inserts into the lower lobe.
Succenturiate lobes can also lie over the cervix as a variant
of placenta previa.
106
Even more important is the
concern over the location of the vascular connection
between the main placenta and the succenturiate lobe. If
the vessels lie in proximity to the cervix, a vasa previa
may be present.
When a succenturiate lobe of the placenta is identified,
it is imperative that the vascular connection between the
succenturiate lobe and placenta be identified. This can
be difficult at times because of poor visualization, especially later in pregnancy, and because the closest distance
between succenturiate lobe and placenta is not always the
route taken by the vessels. At a minimum, the internal
cervical os should be evaluated to assess for fetal vessels.
Bilobed Placenta
Bilobed placentas consist of two similarly sized placental
lobes separated by intervening membranes (Fig. 44-25).
There must be some vascular connection between the
lobes, and the umbilical cord may insert between the
lobes in the membranes. Although rare, a bilobed placenta can be regarded similar to succenturiate lobes, with
similar risks. Bilobed placentas may have more unprotected vessels, however, reinforcing the need for careful
evaluation of the placental vasculature in such cases.
UMBILICAL CORD
Size and Appearance
Umbilical cord length varies, and a normal length has
not been established. However, extremes of cord length
are associated with abnormal outcome. Short umbilical
cords are associated with conditions that impair fetal
movement early in gestation, such as akinesia syndromes,
aneuploidy, and extreme IUGR. Excessive cord length
is associated with asphyxia or death resulting from a
variety of situations that compromise cord flow, including excessive coiling, true knots, multiple loops of nuchal
cord, and cord prolapse.
The potential importance of the diameter of the
umbilical cord is unclear. In the first trimester, fetal size
correlates with cord diameter, and small diameter may
be a marker for pregnancy loss.
tiple centers suggest that cord diameter may be a marker
for chromosomal abnormalities when larger
than expected.
112
In the second and third trimesters, the
110
Also, data from mul-
111
or smaller
largest contributor to the size of the umbilical cord is
Wharton’s jelly. A nomogram has been developed for
the area of Wharton’s jelly that correlate with fetal biometry up to 32 weeks’ gestation.
trimester, a larger-than-expected umbilical cord is associated with aneuploidy.
115
IUGR has been associated with
113,114
In the second
thin cords, and diabetes, fetal macrosomia, placental
abruption, and rhesus isoimmunization have been associated with thicker cords.
fetal umbilical cord size and fetal growth overlap too
greatly to be useful screening tools.
116
The associations between
117
Information on the umbilical cord and its manner of
twisting comes from the pathology literature. Left twists
occur in 83%, right twists in 12%, and absent twists
in 5% of umbilical cords in live-born singletons. For
the umbilical cords that have a twist, ascertainment
of the degree of twist has been reported antenatally.
The umbilical coiling index is calculated by dividing
the number of helices by the cord length in centimeters
1516 PART IV ■ Obstetric Sonography
(Fig. 44-26). The mean umbilical coiling index is
0.44 ± 0.11 antenatally and 0.28 ± 0.08 after delivery.
Umbilical coiling does not vary with respect to the
amount of Wharton’s jelly present.
119
Assessment of
118
the degree of coiling in the second trimester does
not correlate well with the umbilical coiling index
at term.
120
Absent umbilical cord twists are associated with
single umbilical arteries, multiple gestations, fetal demise,
preterm delivery, aneuploidy, and both marginal and
velamentous umbilical cord insertions
Lower degrees of coiling are associated with lesser degrees
of fetal growth.
124
True knots of the umbilical cord occur in 1% to 2%
of pregnancies. Although some are normal variants,
121-123
(Fig. 44-27).
125
these knots may also be associated with increased fetal
mortality. Sonographic features such as the “hanging
noose sign” have been proposed to make this diagnosis
A
FIGURE 44-26. Umbilical coiling index. Defined as the
distance (A) between the same umbilical artery making one turn
around the umbilical vein. (From Otsubo Y, Yoneyama Y, Suzuki
S, et al. Sonographic evaluation of umbilical cord insertion with
umbilical coiling index. J Clin Ultrasound 1999;27:341-344.)
antenatally, with 2-D imaging as well as 3-D and 4-D
sonography.
126,127
Although 3-D sonography may be
helpful for suggesting the presence of a true knot of the
umbilical cord, multiple loops of cord lying next to each
other can mimic the presence of a knot.
128,129
Cysts of the umbilical cord can be seen throughout
pregnancy, occurring most frequently on the portion
closest to the fetus (Fig. 44-28). Many cysts develop
from the allantois and omphalomesenteric duct, or pseu-
docysts may develop through liquefaction of Wharton’s
jelly, giving the umbilical cord a hydropic appear-
130,131
ance
(Fig. 44-29). All cord cysts are associated with
both structural and chromosomal defects, so a detailed
structural survey is required whenever a cyst is encoun-
132
tered.
often resolve, without sequelae.
are the most common chromosomal abnormalities associated with umbilical cord cysts,
and gastrointestinal anomalies are the most common
structural defects.
However, cord cysts seen in the first trimester
135-138
133
Trisomies 13 and 18
131,134
and genitourinary
Vascular anomalies of the umbilical cord are associated with adverse fetal outcomes. Umbilical artery
aneurysms are associated with vascular abnormalities,
trisomy 18, and fetal demise.
rupture of the umbilical artery with a resultant umbilical
cord hematoma has also been reported.
131,139-141
Spontaneous
141
Umbilical cord tumors are exceedingly rare. The most
common is the umbilical cord hemangioma, which
appears as a heterogeneous mass surrounded by multiple
peripheral cystic areas. Cord hematomas are associated
with an increased risk of fetal demise.
142,143
Nuchal cord (cord around neck of fetus) is often seen
in the second and third trimesters. Multiple tight loops
of nuchal cord indenting the skin late in the third trimester should prompt a nonstress test.
FIGURE 44-27. Uncoiled cord in second trimester.
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