Diagnostic ultrasound ( PDFDrive )

CHAPTER 43 Sonographic Evaluation of the Placenta 1483
features such as the “hanging noose sign” have been proposed
to make this diagnosis antenatally, with 2D imaging as well as
3D and 4D sonography. 147,148 Although 3D 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. 149,150
Cysts of the umbilical cord can be seen throughout pregnancy,
occurring most frequently on the portion closest to the fetus
(Fig. 43.28). Many cysts develop from the allantois and omphalomesenteric
duct, or pseudocysts may develop through liquefaction
of Wharton jelly, giving the umbilical cord a hydropic
appearance 151,152 (Fig. 43.29). All cord cysts are associated with
both structural and chromosomal defects, so a detailed structural
survey is required whenever a cyst is encountered. 153 However,
cord cysts seen in the irst trimester oten resolve, without
sequelae. 154 Trisomies 13 and 18 are the most common chromosomal
abnormalities associated with umbilical cord cysts, 152,155
and genitourinary and gastrointestinal anomalies are the most
common structural defects. 156-159
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. 152,160-162 Spontaneous rupture of the umbilical artery
with a resultant umbilical cord hematoma has also been
reported. 162
Umbilical cord tumors are exceedingly rare. he 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. 163,164
Nuchal cord (cord around neck of the fetus) is oten seen in
the second and third trimesters and is a common inding at
delivery. Multiple tight loops of nuchal cord indenting the skin
late in the third trimester may prompt further evaluation
A
B
C
FIG. 43.28 Umbilical Cord Cysts. (A) Transvaginal sonogram
early in the irst trimester demonstrates the yolk sac (long arrow),
which is extraamniotic, and umbilical cord cyst (short arrow).
(B) Transvaginal sonogram of a irst-trimester fetus with an umbilical
cord cyst (calipers), which is near the abdominal umbilical cord
insertion site. (C) Color Doppler sonogram with low in the umbilical
cord around the cyst.