AJR 2000; 174:641-649
© American Roentgen Ray Society
Sonography of Obstetric and Gynecologic Emergencies
Part I, Obstetric Emergencies
Y. Kaakaji1,
H. V. Nghiem2,
C. Nodell1 and
T. C. Winter3
1
Department of Radiology, The University of Washington Medical Center, 1959
N.E. Pacific St., Seattle, WA 98195-7115.
2
Department of Radiology, University of Michigan Health System, 1500 E. Medical
Center Dr., TC2910Q, Ann Arbor, MI 48109-0326.
3
Department of Radiology, University of Wisconsin Hospital, E3/311, CSC 600
Highland AVe., Madison, WI 53792-3252.
Received June 8, 1999;
accepted after revision August 10, 1999.
Address correspondence to H. V. Nghiem.
Introduction
Pelvic pain and vaginal bleeding are two of the most common presenting
complaints of women examined in the emergency department. In addition to
clinical history, physical examination, and laboratory data, sonography is
essential in evaluating pelvic pain and vaginal bleeding in women of
childbearing age because many causes of these two presentations have
suggestive or definitive sonographic findings. Multiple nonobstetric and
nongynecologic problems may present with a similar clinical scenario. The
purpose of this paper is to describe the pathophysiology and the sonographic
features of obstetric emergencies.
Ectopic Pregnancy
Ectopic pregnancy remains a common cause of morbidity and mortality in
women of childbearing age, despite advances in both diagnosis and therapy. The
diagnosis of ectopic pregnancy must be excluded in every woman of childbearing
age who has positive findings on a pregnancy test, despite the clinical
presentation, particularly when the human chorionic gonadotropin level lags
behind the estimated gestational age. An early intrauterine pregnancy,
spontaneous abortion, or ectopic pregnancy can all present with an empty
uterus. Common sonographic findings include one or a combination of the
following: cystic or solid adnexal mass, dilated and thick-walled fallopian
tube (adnexal ring), free echogenic or sonolucent intraperitoneal fluid,
hematosalpinx, and an extrauterine gestational sac containing a yolk sac with
or without an embryo [1] (Figs.
1 and
2). Color-flow Doppler imaging
may be helpful with diagnosis of ectopic pregnancy when a trophoblastic
Doppler flow signal is present. Taylor et al.
[2] reported trophoblastic flow
signals (high velocity, low impedance flow) in 54% of ectopic pregnancies in
their series. In a patient with a positive pregnancy test, the isolated
finding of free intraperitoneal fluid in the presence of an empty uterus has
been shown to carry a 69% specificity and a 63% sensitivity for the diagnosis
of an extrauterine gestation
[1]. In particular, echogenic
fluid has a positive predictive value of 93% for the presence of a bleeding or
ruptured ectopic pregnancy. No reliable sonographic findings currently exist
to predict the status of the fallopian tube because the volume of
hemoperitoneum does not correlate with tubal rupture. A large volume of
hemoperitoneum may also occur with active bleeding from the tubal fimbria,
tubal abortion, or rupture of the corpus luteum of pregnancy
[3]. The identification of an
intradecidual sign (a well-defined fluid collection completely surrounded by
decidual tissue and adjacent to, but not deforming, the central cavity echo
complex) is suggestive of an intrauterine gestation, with a limited
sensitivity of 34-66% and specificity of 55-73%
[4] (Fig.
3A,3B).
The double-decidual sign that can be used to identify an intrauterine
pregnancy before visualization of the yolk sac or embryo must be distinguished
from the decidual cast or pseudogestational sac of ectopic pregnancy. A
decidual cast or pseudogestational sac is an intrauterine fluid collection
surrounded by a single decidual layer rather than the two concentric rings of
the double-decidual sign of intrauterine pregnancy.
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Fig. 2. —26-year-old woman with live tubal ectopic pregnancy. Endovaginal
sonogram shows live right-sided tubal ectopic pregnancy with "ring of
fire" sign of trophoblastic flow as indicated by Doppler tracing
waveform. Arrowhead points to embryo with positive cardiac activity at
real-time.
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Fig. 3B. —22-year-old woman with live right-sided tubal ectopic pregnancy.
Endovaginal sonogram of right adnexa shows extraovarian echogenic ring
(arrow) containing live embryo; corpus luteum of pregnancy is seen in
right ovary (RT OV) (arrowhead). Determination of extraovarian
location of ectopic pregnancy may be suggested by indentation seen at
interface of ovary and ectopic pregnancy or by plane of separation between
ovary and ectopic pregnancy. Rim of ovarian tissue surrounding portion of mass
would be characteristic of intraovarian location. UT = uterus.
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The identification of a normal or abnormal intrauterine pregnancy virtually
excludes the diagnosis of ectopic pregnancy. The risk of concomitant
intrauterine pregnancy and ectopic pregnancy (Fig.
4A,4B,4C)
in the general population is low, 1:400 to 1:30,000. However, this risk is
higher, 1:100, in patients with assisted reproduction
[5].
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Fig. 4A. —Concomitant intrauterine and ectopic pregnancy in 32-year-old woman
not taking fertility drugs. Sagittal transabdominal sonogram shows
intrauterine gestation with yolk sac (arrowhead).
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Fig. 4B. —Concomitant intrauterine and ectopic pregnancy in 32-year-old woman
not taking fertility drugs. Transabdominal sonogram of right adnexa shows
tubal ring (arrows) with adjacent free fluid (ff).
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Fig. 4C. —Concomitant intrauterine and ectopic pregnancy in 32-year-old woman
not taking fertility drugs. Endovaginal sonogram of tubal ring
(arrows) in right adnexa shows that it contains embryo
(calipers), which was alive on color Doppler sonography.
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Sonography is valuable in characterizing extratubal ectopic gestations such
as intraabdominal (Fig.
5A,5B),
cervical, and cornual pregnancy. Cornual, or interstitial, gestations account
for as many as 3% of all ectopic pregnancies and carry a high mortality rate
as a result of delayed rupture with extensive hemorrhage
[6]. Original sonographic
descriptions include an eccentric intrauterine location and thinning of the
surrounding myometrial mantle to less than 5 mm
[6,7]
(Fig.
6A,6B,6C).
The interstitial line (a thin echogenic line extending from the endometrial
canal to the cornual sac or hemorrhagic mass) has been described as a highly
specific and sensitive sign of interstitial pregnancy
[8]. Ackerman et al.
[8] saw this interstitial line
in 92% of interstitial ectopic pregnancies in a retrospective 7-year study.
Asymmetrically increased low-resistance flow in a uterine cornu may also be a
secondary sign of an interstitial pregnancy
[8]. Care must be exercised to
avoid misinterpreting a normal intrauterine pregnancy in an anomalous
uterus—such as a septate or bicornuate uterus—as an interstitial
pregnancy. Cervical pregnancies have a worse prognosis than tubal pregnancies
because of the potential for uncontrollable hemorrhage. Once a gestational sac
is identified in the cervix, a crucial part of diagnosis is to differentiate a
cervical pregnancy from an abortion in progress. Features characteristic of a
cervical pregnancy include a round or oval noncrenated sac, the presence of
fetal cardiac activity, a closed internal os, and constant sac shape and
location on close follow-up sonograms.
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Fig. 5A. —32-year-old woman with intra abdominal pregnancy. Transverse
transabdominal sonogram shows empty uterus with thickened endometrium. Free
intraperitoneal fluid (ff) and extrauterine pregnancy is seen. Arrows point to
fetal skull.
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Fig. 6C. —33-year-old woman with surgically proven left cornual pregnancy.
Oblique sagittal endovaginal sonogram oriented toward left cornu reveals
echogenic ring (arrows) with near absence of surrounding
myometrium.
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Cervical Incompetence
Cervical incompetence is a common cause of pregnancy failure in the second
trimester, manifesting as painless dilatation of the cervix that leads to
preterm labor. Cervical incompetence may present with premature rupture of
membranes, resulting in oligohydramnios. The sonographic findings include
bulging of the fetal membranes into a widened internal os and shortening of
the cervical canal (Fig. 7).
The cervical length is obtained by measuring the endocervical canal from the
internal cervical os to the external cervical os. Endovaginal sonography does
not have the distortion associated with the transabdominal approach and is a
more accurate method. The mean cervical length is normally greater than 3 cm.
Because of the dynamic nature of the cervical canal and lower uterine segment
throughout pregnancy, the normal length of a competent cervix falls within a
wide range [9]. Consequently,
the sonographic assessment of the cervix requires attention to the temporal
changes of the cervical length during every examination (Fig.
8A,8B).
Furthermore, provocative measurements such as Valsalva's maneuver or manual
compression of the uterine fundus may corroborate the sonographic diagnosis of
cervical incompetence [10].
The sonographic determination of the residual closed length of the cervix may
be used as a prognostic indicator for the risk of preterm labor progressing
into preterm delivery [9].
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Fig. 8A. —34-year-old woman with second trimester cervical incompetence,
emphasizing dynamic nature of cervix during pregnancy. Sagittal endovaginal
sonogram shows shortened endocervical canal (calipers), with
funneling of internal os (arrowhead).
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Fig. 8B. —34-year-old woman with second trimester cervical incompetence,
emphasizing dynamic nature of cervix during pregnancy. Second image obtained
during same examination as A reveals progressive shortening of
endocervical canal (calipers) and further widening of internal os
(arrowheads).
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Retroplacental Hematoma and Abruptio Placentae
Bleeding along the basal plate of the placenta, separating it from the
underlying uterine wall, may result from primary abruptio placentae or
ruptured spiral arteries. Proposed causes of ruptured spiral arteries include
maternal hypertension, trauma, cigarette smoking, acute chorioamnionitis,
retroplacental myomas, and ethanol or cocaine abuse. Fetal demise is commonly
a result of global placental infarction from the rupture of spiral arteries or
extrinsic compression by the retroplacental hematoma when a large portion of
the maternal placental surface is involved
(Fig. 9). Retroplacental
hematoma may remain asymptomatic or present as placental abruption with
painful vaginal bleeding, consumptive coagulopathy, acute renal failure
resulting from acute tubular or cortical necrosis, and fetal distress. Vaginal
hemorrhage occurs with large retroplacental hematomas once the peripheral
margins of the placenta are disrupted and the fetal membranes are stripped
from the underlying decidua basalis. Fetal demise is uncommon with vaginal
hemorrhage because the overlying placenta is not significantly compressed.
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Fig. 9. —Placental abruption and fetal demise in 28-year-old woman presenting
with acute pelvic pain without vaginal bleeding in early second trimester.
Endovaginal sonogram shows apparent thickening of placenta (arrow),
consistent with retroplacental hematoma. No fetal heart motion was identified.
Retroplacenta abruption may appear simply as thickened placenta.
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Sonographically, the retroplacental hematoma may mimic a thickened placenta
because the hematoma is commonly isoechoic to the placenta. Otherwise, the
retroplacental hematoma may be hypoechoic or may be of heterogeneous
echogenicity (Fig. 10).
Because of the low sensitivity of sonography in detecting small retroplacental
or submembranous hematomas or the occasional absence of bleeding with
placental abruption, negative sonographic findings do not rule out the
presence of placental abruption
[11].
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Fig. 10. —32-year-old woman in second trimester with placental abruption
presenting with vaginal bleeding. Sagittal transabdominal sonogram shows
thickened anterior placenta with extremely heterogeneous echo texture. Portion
of placenta closest to maternal surface (arrowheads) is much more
hypoechoic than remainder of placenta (arrows), which is more
suggestive of retroplacental abruption. After spontaneous abortion,
histopathologic examination revealed placental abruption with infarct
involving at least 50% of placenta.
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Uterine Dehiscence and Rupture
Although uterine rupture may occur in previously normal uteri, old cesarean
scars most commonly cause uterine dehiscence. Uterine rupture may be limited
to dehiscence of the ends of the cesarean scar with an intact overlying
serosal layer of the uterine wall. This type of dehiscence does not involve
extrusion of fetal parts into the peritoneal cavity, and therefore results in
minimal vaginal bleeding or intraperitoneal hemorrhage. Conversely,
full-thickness uterine rupture, with direct communication of the uterine and
peritoneal cavities, results in massive hemoperitoneum and carries high fetal
and maternal morbidity and mortality rates. Classic scars are more likely to
rupture before labor, whereas lower uterine segment scars tend to rupture
after labor. Reported sonographic signs of uterine rupture include the
identification of the protruding portion of the amniotic sac, an endometrial
or myometrial defect, an extrauterine hematoma, and hemoperitoneum
[12],
[13] (Figs.
11A,11B
and
12A,12B,12C).
Multiplanar MR imaging offers a comprehensive assessment of the uterine wall
and the peritoneal cavity [14]
(Fig.
12A,12B,12C).
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Fig. 11B. —36-year-old woman with uterine rupture after prolonged induction of
vaginal delivery. Transverse image of pelvis shows complex hematoma. Complex
fluid collection and clinical symptoms suggested diagnosis. Uterine rupture
was confirmed at surgery.
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Fig. 12A. —28-year-old woman with surgically proven intraabdominal pregnancy
resulting from uterine dehiscence because anterior placenta percreta grew
anteriorly through previous cesarean scar. Sagittal endovaginal sonogram shows
empty uterus, myometrial defect anteriorly and inferiorly (long
arrows), and extrauterine pregnancy. Arrowhead points to fetal abdomen.
Short arrows indicate endometrium.
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Fig. 12B. —28-year-old woman with surgically proven intraabdominal pregnancy
resulting from uterine dehiscence because anterior placenta percreta grew
anteriorly through previous cesarean scar. Sagittal T2-weighted MR image shows
empty uterus (arrowhead) and extrauterine amniotic sac
(asterisk). Arrows indicate myometrial defect.
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Fig. 12C. —28-year-old woman with surgically proven intraabdominal pregnancy
resulting from uterine dehiscence because anterior placenta percreta grew
anteriorly through previous cesarean scar. Sagittal gradient-echo MR image
shows multiple parasitized vessels (wavy arrow) around extrauterine
pregnancy (straight arrows).
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Puerperal Gonadal Vein Thrombosis
Ovarian vein thrombosis is an uncommon, but potentially fatal, postpartum
complication. The pathogenesis is postulated to be retrograde propagation of
thrombosed myometrial veins draining an infected placenta. The diagnosis is
critical to make in postpartum patients because of the risk of pulmonary
embolism.
The sonographic diagnosis of ovarian vein thrombosis is mainly based on
identifying the dilated, noncompressible ovarian vein extending into the
inferior vena cava in a postpartum woman with signs of infection
[15] (Fig.
13A,13B,13C).
Confirming the gonadal vein drainage into the inferior vena cava is important
to avoid mistaking the dilated vein for a dilated ureter, dilated fallopian
tube, or retrocecal appendicitis
[16]. The lateral displacement
of the ovarian vein by the gravid uterus and its tortuous course during
pregnancy may further mimic the sonographic appearance of bowel with thickened
wall or appendicitis [16]. The
venous thrombosis may extend in a retrograde fashion into the iliofemoral
veins, potentially mimicking lower extremity deep venous thrombosis.
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Fig. 13A. —28-year-old woman with puerperal gonadal vein thrombosis presenting
as persistent fever 3 days after uncomplicated vaginal delivery. Sequential
axial enhanced CT images show postpartum uterus (U, A and B),
enlarged heterogeneous ovary (arrow, A), dilated tortuous
right ovarian vein with partial thrombosis (arrowhead, B), and
partial thrombosis in pararenal inferior vena cava (arrow,
C).
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Fig. 13B. —28-year-old woman with puerperal gonadal vein thrombosis presenting
as persistent fever 3 days after uncomplicated vaginal delivery. Sequential
axial enhanced CT images show postpartum uterus (U, A and B),
enlarged heterogeneous ovary (arrow, A), dilated tortuous
right ovarian vein with partial thrombosis (arrowhead, B), and
partial thrombosis in pararenal inferior vena cava (arrow,
C).
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Fig. 13C. —28-year-old woman with puerperal gonadal vein thrombosis presenting
as persistent fever 3 days after uncomplicated vaginal delivery. Sequential
axial enhanced CT images show postpartum uterus (U, A and B),
enlarged heterogeneous ovary (arrow, A), dilated tortuous
right ovarian vein with partial thrombosis (arrowhead, B), and
partial thrombosis in pararenal inferior vena cava (arrow,
C).
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Retained Products of Conception
Retained products of conception after spontaneous or elective abortion or
full-term pregnancy may cause secondary postpartum hemorrhage or may serve as
a nidus for uterine infection. Predisposing factors include the presence of a
succenturiate lobe or placenta accreta, increta, or percreta, preventing
complete placental delivery. Sonographic findings include endometrial
expansion of heterogeneous echogenic material (Fig.
14A,14B)
and focal areas of hyperechogenicity that may represent retained placental
calcifications (Fig. 15).
Retained trophoblastic tissue exhibits low-resistance arterial flow, which is
uncommonly seen with endometritis.
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Fig. 14A. —28-year-old woman with retained products of conception presenting as
persistent vaginal bleeding after spontaneous abortion. Sagittal endovaginal
color Doppler sonograms show expanded and heterogeneous endometrium
(arrowheads, A) and marked trophoblastic flow.
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Fig. 14B. —28-year-old woman with retained products of conception presenting as
persistent vaginal bleeding after spontaneous abortion. Sagittal endovaginal
color Doppler sonograms show expanded and heterogeneous endometrium
(arrowheads, A) and marked trophoblastic flow.
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Introduction
Ectopic Pregnancy
