Diagnostic ultrasound ( PDFDrive )

CHAPTER 43 Sonographic Evaluation of the Placenta 1473
and can approach the echogenicity of the myometrium. An
indirect sign of the presence of an acute hematoma is apparent
thickening of the placenta, which is associated with worse
outcome. 99,100
Even though placental abruption remains a clinical diagnosis,
ultrasound can play an important role. Larger hematomas are
expected to be seen (Fig. 43.15), and these are more likely to be
clinically important. Glantz and Purnell 101 reported that the
identiication of placental abruption by ultrasound had a sensitivity,
speciicity, positive predictive value, and negative predictive
value of 24%, 96%, 88%, and 53%, respectively. hey determined
that if a hematoma was identiied by sonography, there was an
increased risk of preterm delivery, low birth weight, and neonatal
intensive care unit admission. Increased size of the hematoma
and percentage of placental involvement are associated with
increased fetal mortality. 102
PLACENTAL INFARCTION
Placental infarctions can occur focally or throughout the placenta
and are thought to have a vascular etiology. Maternal loor
infarction is a difuse entity overtaking the villi with a ibrinoid
deposition at the maternal surface and basal plate, reaching into
the placental substance. he presence of this ibrin surrounding
the villi obstructs nutrient exchange from mother to fetus. Both
FIG. 43.9 Placenta Percreta. Transvaginal sonogram of a thirdtrimester
placenta shows loss of the hypoechoic border between the
placenta and the myometrium, with protrusion of the placenta (long
arrow) into the maternal bladder (arrowhead); short arrow, placental
lake.
FIG. 43.11 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. (With permission from Levine D. Placenta accreta:
evaluation with color Doppler, power Doppler and fast MRI. Radiology.
1997;205:773-776. 89 )
A
B
FIG. 43.10 First-Trimester Placenta Accreta. (A) The umbilical cord insertion is low in the uterus; arrowheads indicate multiple small placental
lakes. This patient had a prior cesarean delivery and subsequently was shown to have a placental previa accreta. (B) A different patient with two
prior cesarean deliveries. Note bulging of the placental tissue in the scar from a prior cesarean into the posterior wall of the bladder (arrows).