Role of Ultrasound in Emergency Obstetrics

Dr. Omneya Nagy ElmakhzangySpecial Fetal Care UnitAin Shams University

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

Pregnancy of unknown location (PUL)

The term PUL is used whenever there is no sign of either intra or extrauterine pregnancy or retained products of conception on transvaginal ultrasound.

Up to 31% of women attending early pregnancy assessment centers have a PUL though the experience of the sonographer can reduce this to 10%.

Early IUP??

Ectopic pregnancy??

PUL??

How can Ultrasound answer the Question?

Discriminatory zoneIt refers to a defined level of hCG above which the

gestational sac of an intrauterine pregnancy should be visible on ultrasound.

The concept of a discriminatory zone has limitations. Levels of hCG of 1000 iu/l, 1500 iu/l and 2000 iu/l have been used as discriminatory levels.

These levels are dependent upon the quality of the ultrasound equipment, the experience of the sonographer, prior knowledge of the woman’s risks.

For specialised units performing high resolution vaginal ultrasound with prior knowledge of the woman’s symptoms and serum hCG, a discriminatory zone of 1000 iu/l can be used. In other units offering a diagnostic transvaginal scan without prior clinical or biochemical knowledge a discriminatory zone of 1500 iu/l or 2000 iu/l is acceptable.

RCOG Guideline No. 21 ,Evidence level III (2004)

Different Scanning Modalities

Gestational sac TAUS

Gestational sac TVUS

3 D Scanning

Endometrial Findings Suggestive of intrauterine Pregnancy

Double decidual sac sign (DDSS)Is a useful feature on early pregnancy

ultrasound in distinguishing between an early intrauterine pregnancy (IUP) and a pseudogestational sac. It consists of the decidua parietalis (that lining the uterine cavity) and decidua capsularis (lining the gestational sac).

Endometrial findings diagnostic of intrauterine pregnancy.

Adenxae and ovaries

Corpus luteum

Tubal Ectopic pregnancy

Adenxal mass

Adenxal ectopic pregnancy with positive cardiac pulsation

Interstitial pregnancyCornual, 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 . Original sonographic descriptions include an eccentric intrauterine location and thinning of the surrounding myometrial mantle to less than 5 mm.

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

Ovarian Ectopic

Cervical EctopicCervical 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 sonogram

Cervical Ectopic

Heterotropic Pregnancy

Abdominal Ectopic

Peritoneal cavity free pelvic fluid or haemoperitoneum in the pouch of DouglasThe presence of free intraperitoneal fluid in the

context of a positive beta HCG and empty uterus is ~70% specific for an ectopic pregnancy . ~63% sensitive for an ectopic pregnancy.

The differential diagnosis of abdominal pain in a pregnant patient is broad. An ectopic pregnancy must be excluded with ultrasound. Other common diagnoses in this setting include:

1- Ruptured corpus luteum.2-Appendicitis (negative beta hCG).

Peritoneal Free Fluid

Case : Ruptured corpus Letuem Cyst with massive heamopertonium

Ring of fire SignThe ring of fire sign also known as ring of

vascularity signifies a hypervascular lesion with peripheral vascularity on colour or pulsed Doppler examination of pelvis due to low impedance high diastolic flow .

This sign can be seen in highly vascular pelvic lesions like:

1-corpus luteum cyst (more commonly)2-ectopic pregnancy

Cervical IncompetenceCervical 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.

Failed early Pregnancy Findings diagnostic of pregnancy failurecrown-rump length (CRL) of ≥7 mm and no

heart beatmean sac diameter (MSD) of ≥25 mm and no

embryoabsence of embryo with heartbeat ≥2 weeks

after a scan that showed a gestational sac without a yolk sac

absence of embryo with heartbeat ≥11 days after a scan that showed a gestational sac with a yolk sac

Findings suspicious but not diagnostic of pregnancy failure

crown-rump length (CRL) of <7 mm and no heartbeatmean sac diameter (MSD) of 16-24 mm and no embryoabsence of embryo with heartbeat 7-13 days after a

scan that showed a gestational sac without a yolk sacabsence of embryo with heartbeat 7-10 days after a

scan that showed a gestational sac with a yolk sacabsence of embryo ≥6 week after last menstrual

periodempty amnion (amnion seen adjacent to yolk sac, with

no visible embryo)enlarged yolk sac (>7 mm)small gestational sac in relation to the size of the

embryo (<5 mm difference between mean sac diameter and crown-rump length)

Retained Products of ConceptionRetained 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 and focal areas of hyperechogenicity that may represent retained placental calcifications . Retained trophoblastic tissue exhibits low-resistance arterial flow, which is uncommonly seen with endometritis

Retroplacental Hematoma and Abruptio PlacentaeSeparation of the placenta from the myometrium

where it is implanted causes bleeding. When only the margin of the placenta is separated, it is called a marginal subchorionic hematoma .

When the bleeding is behind the placenta, it is termed a retroplacental bleed. The term “abruption” (abruptio placentae) is typically reserved for premature placental separation occurring after 20 weeks.

Subamniotic bleeding is a collection anterior to the placenta and limited by the umbilical cord.

Subchorionic hematoma .Subchorionic hematomas manifest as crescentic collections lifting the chorionic membrane Depending on the time elapsed since the bleeding, the collection will have variable echotexture and size .Correlation between the size of the subchorionic hematoma and the rate of pregnancy loss is imperfect. In general, small- and moderate-sized subchorionic hematomas have a better outcome than large ones . The percentage of placental detachment is the prognostic factor most strongly associated with fetal mortality: the frequency of fetal demise is 50% for retroplacental hematoma versus 7% for marginal subchorionic hematoma

Subamniotic hematoma Subamniotic hematomas result from the rupture of chorionic vessels (fetal vessels) close to the cord insertion. These lesions are rarely reported in utero; they are usually discovered postnatally and thought to result from excessive traction on the umbilical cord at birth. It has been postulated that these cysts may form from subchorionic fibrin deposition 

Retroplacental hematoma (abruptio placentae)Abruptio placentae is one of the most serious complications of pregnancy, accounting for up to 25% of perinatal deaths , Diagnosis requires a high index of suspicion because the signs and symptoms are variable, including a painful tense uterus, vaginal bleeding, premature labor, fetal distress, and coagulopathy; most episodes remain asymptomatic. Sonographic findings are negative in most cases, either because of the passage of blood without accumulation behind the placenta or because of blood being isoechoic with the placenta. The only evidence of abruption may be the identification of an abnormally thick placenta . The sensitivity of sonography is low, 2–20%.

Placenta Previa Routine ultrasound scanning at 20 weeks of gestation should include placental

localisation.

Transvaginal scans improve the accuracy of placental localisation and are safe, so the suspected diagnosis of placenta praevia at 20 weeks of gestation by abdominal scan should be confirmed by transvaginal scan.

In the second trimester transvaginal sonography (TVS) will reclassify 26–60% of cases where the abdominal scan diagnosed a low-lying placenta, meaning fewer women will need follow-up. In the third trimester, TVS changed the transabdominal scan diagnosis of placenta praevia in 12.5% of 32 women. Leerentveld et al demonstrated high levels of accuracy of TVS in predicting placenta praevia in 100 women suspected of having a low-lying placenta in the second and third trimester (sensitivity 87.5%, specificity 98.8%, positive predictive value 93.3%, negative predictive value 97.6% .

RCOG Green-top Guideline No. 27

All women require follow-up imaging if the placenta covers or overlaps the cervical os at 20 weeks of gestation. Women with a previous caesarean section require a higher index of suspicion as there are two problems to exclude: placenta praevia and placenta accreta. If the placenta lies anteriorly and reaches the cervical os at 20 weeks, a follow-up scan can help identify if it is implanted into the caesarean section scar.

Placental ‘apparent’ migration, owing to the development of the lower uterine segment, occurs during the second and third trimesters, but is less likely to occur if the placenta is posterior or if there has been a previous caesarean section.

In cases of asymptomatic women with suspected minor praevia, follow-up imaging can be left until 36 weeks of gestation.

In cases with asymptomatic suspected major placenta praevia or a question of placenta accrete, imaging should be performed at around 32 weeks of gestation to clarify the diagnosis and allow planning for third-trimester management, further imaging and delivery

RCOG Green-top Guideline No. 27

Morbidly adherent placenta

Sensitivity (%)

Specificity (%)

Positive predictive value (%)

Risk

Grey scale 95 76 82 93

Colour Doppler

92 68 76 89

Three-dimensional power Doppler

100 85 88 100

RCOG Green-top Guideline No. 27

Abnormal intraplacental lacunaeVisualization of lacunae had the highest sensitivity (79%) in

the 15–20-week range and a sensitivity of 93% in the 15–40-week gestational age time frame (ISUOG 2005).

Myometrial thickness Measurement of the thickness of the lower uterine segment in

women who had had a previous Cesarean section and had a low-lying anterior placenta or placenta previa by measuring between the bladder wall and the retroplacental vessels, as seen by color Doppler.

All patients later proven to have placenta accreta had myometrium of less than 1 mm, which was as predictive of accreta as lacunae

Translucency zone

Color Doppler

Color Doppler image of a tornado-shaped sinus

Signs Suggestive of Placental invasion by 3D Power Doppler Numerous coherent vessels involving the whole uterine

serosa–bladder junction (basal view)Hypervascularity (lateral view)Inseparable cotyledonal and intervillous circulations, chaotic

branching, detour vessels (lateral view).

Uterine Dehiscence and RuptureAlthough 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

Sagittal transabdominal sonogram shows enlargement and heterogenicity of postpartum uterus.

An unusual cause of abdominal pain and shock in pregnancy is Spontaneous uterine rupture caused by placenta percreta in first and second trimester.

Red or carneous fibroid degeneration Is one of a five main types degeneration that

can involve a uterine leiomyoma. While it is an uncommon type degeneration it is thought to be most common form of degeneration of a leiomeyoma during pregnancy.

Fetal Emergency

Is an obstetric complication in which fetal blood vessels cross or run in close proximity to the external orifice of the uterus. These vessels are at risk of rupture when the supporting membranes rupture, as they are unsupported by the umbilical cord or placental tissue.

 If these fetal vessels rupture the bleeding is from the fetoplacental circulation, and fetal exsanguination will rapidly occur, leading to fetal death.

Vasa Previa

 On ultrasound and gross examination, the normal umbilical cord sheath is contiguous with the chorionic plate. With a velamentous insertion, the cord can end several centimeters from the placenta, at which point the umbilical vessels separate from each other and cross between the amnion and chorion before connecting to the subchorionic vessels of the placenta . This typically occurs at the margin of the placenta (within 1 cm of the placental edge), but can also occur at the apex of the gestational sac. In monochorionic twins, the velamentous vessels often occur in the dividing membranes.

Diagnosis of Fetal Distress by Ultrasound In the preterm SGA fetus with umbilical artery

AREDV detected prior to 32 weeks of gestation, delivery is recommended when DV Doppler becomes abnormal or UV pulsations appear, provided the fetus is considered viable and after completion of steroids. Even when venous Doppler is normal, delivery is recommended by 32 weeks of gestation and should be considered between 30–32 weeks of gestation.

RCOG Green-top Guideline No. 31 January 2014

If MCA Doppler is abnormal but U.A is reserved , delivery should be recommended no later than 37 weeks of gestation.

RCOG Green-top Guideline No. 31 January 2014

When umbilical artery Doppler flow indices are abnormal (resistance index > +2 SDs above mean for gestational age) and delivery is not indicated repeat surveillance twice weekly in fetuses with end–diastolic velocities present and daily in fetuses with absent/reversed end–diastolic frequencies.

RCOG Green-top Guideline No. 31 January 2014

Nuchal Cord

Nuchal cord is very common, present in 20% to 30% of birth.

The presence of two or more coils is estimated to affect 2.5-8.3 % of all pregnancies.

Single Nuchal cord usually doesn’t compromise the fetal well being and so management should not be altered

Multiple Nuchal cords , esp. 4 or more should be managed with special care because of high risk of cord compression.