Ultrasonography and Doppler 3rd Year Lecture 2012

7/31/2019 Ultrasonography and Doppler 3rd Year Lecture 2012

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ULTRASONOGRAPHY AND DOPPLER

Far Eastern UniversityDr. Nicanor Reyes Medical Foundation

Department of Obstetrics and Gynecology


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ULTRASONOGRAPHY

INOBSTETRICS


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Technology

picture displayed is produced by SOUND WAVESreflected back from the imaged structure

a transducer containing piezoelectric crystals

converts electrical energy to high-frequency

sound waves

water-soluble gel- as a coupling agent

Dense tissue (bone) produces high-velocity

reflected waves- WHITE

Fluid- generates few reflected waves- BLACK


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Technology

Images are generated quickly (> 40

frames/sec) picture appear real-time.

Higher-frequency transducers- better image

resolution

Lower- frequencies penetrate tissue more

effectively but resolution is poor


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Safety

only for valid medical indication

no confirmed damaging biological effects inmammalian tissue

no fetal harm has been demonstrated in morethan 30 years of use


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Clinical Applications

ACCURATE ASSESSMENT OF:

GESTATIONAL AGEFETAL GROWTH

FETAL AND PLACENTAL ANOMALIES

AOG based on ultrasound

- more accurate than the LMP

reduction in the number of labor inductions forpostterm pregnancy AND avoidance of deliveringa premature baby


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Table 162. Components of Standard Ultrasound Examination by Trimester

FIRST TRIMESTER SECOND AND THIRD TRIMESTER

Gestational sac location Fetal number

Embryo or yolk sac identification Presentation

Crown-rump length Fetal heart motion

Cardiac activity Placental location

Fetal number, including number of

amnions and chorions of multiples

when possible

Amnionic fluid volume

Gestational age assessment

Fetal weight estimation

Uterus, adnexal, and cul-de-sac

evaluation

Evaluation for maternal pelvic

masses

Fetal anatomic survey


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Some Indications for First-Trimester

Ultrasound Examination

Confirm intrauterine pregnancy

Evaluate suspected ectopic pregnancy

Estimate gestational age (most accurate)

Diagnose or evaluate multiple gestations

Confirm cardiac activity Assist to chorionic villus sampling, embryo transfer, and

localization and removal of intrauterine device

Evaluate suspected gestational trophoblastic disease

Define cause of vaginal bleeding Evaluate pelvic pain

Evaluate maternal pelvic masses or uterine abnormalities


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First Trimester

Transabdominal Scan

Gestational sac 6 weeks

Fetal echoes & cardiac activity

7 weeks

Transvaginal Scan

Gestational sac

5 weeks Fetal echoes & cardiac activity 6 weeks


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First Trimester Diagnosis ofpregnancy viability

TVS: cardiac motion usually is observed when theembryo is 5 mm in length (CRL)

valuable in diagnosing abnormalities such asembryonic demise as well as anembryonic gestation

Multifetal gestation can be identified- OPTIMAL TIMEto determine chorionicity

BEST TIME to evaluate the uterus, adnexal structures,and cul-de-sac

Between 11-14 weeks- fetal nuchal translucencycan beaccurately- often in conjunction with maternal serummarkers, in the detection ofaneuploidy


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Table 163. Some Indications for Second- or Third-Trimester Ultrasound

Examination

Estimation of gestational ageEvaluation of fetal growth

Vaginal bleeding

Abdominal or pelvic pain

Incompetent cervixDetermination of fetal presentation

Suspected multiple gestation

Adjunct to amniocentesis

Significant uterine size or clinical dates discrepancy

Pelvic mass

Suspected molar pregnancy

Adjunct to cervical cerclage


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Table 163. Some Indications for Second- or Third-Trimester Ultrasound

Examination

Suspected ectopic pregnancy

Suspected fetal death

Suspected uterine abnormality

Evaluation of fetal well-being

Suspected hydramnios or oligohydramnios

Suspected abruptio placentaeAdjunct to external cephalic version

Preterm prematurely ruptured membranes or preterm labor

Abnormal biochemical markers

Follow-up observation of identified fetal anomalyFollow-up evaluation of placental location for suspected placenta previa

History of previous congenital anomaly

Serial evaluation of fetal growth in multifetal gestation

Evaluation of fetal condition in late registrants for prenatal care


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Table 164. Essential Elements of a Standard Examination of Fetal Anatomy

Head and Neck

Cerebellum

Choroid plexus

Cisterna magna

Lateral cerebral ventricles

Midline falx

Cavum septi pellucid

Chest

Four-chamber view of heart

Evaluation of both outflow tracts if technically feasible

Abdomen

Stomachpresence, size, and location

Kidneys

Bladder

Umbilical cord insertion into fetal abdomen

Umbilical cord vessel number

Spine

Cervical, thoracic, lumbar, and sacral spine

Extremities

Legs and armspresence or absence

Gender

Indicated in low-risk pregnancies only for evaluation of multiple gestations


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Fetal Biometry

formulas and nomograms allow accurate assessment of

gestational age

describe normal growth of fetal structures

provides an estimated gestational age from the crown-rump

length measurement in the first trimester

estimates both gestational age and fetal weight in the second

and third trimester using measurements of the biparietal

diameter, head circumference, abdominal circumference, and

femur length.


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Fetal Measurements

Gestational sac (GS) - 4

6 weeks

Crown-Rump Length(CRL) - most accurate at 6-10 weeks

CRL- obtained in a sagittal plane and include neither the yolksac nor a limb bud; variation of only 3 to 5 days


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Fetal Measurements

Biparietal Diameter (BPD) - at 14- 26 weeks, is usually themost accurate parameter, with a variation of 7 to 10 days

BPD- outer edge of the proximal skull to the inner edge of the

distal skull, at the level of the thalami and cavum septumpellucidum

Head circumference (HC) - If the head shape is flattened

(dolichocephaly) or rounded (brachycephaly), thismeasurement is more reliable than the BPD


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Transthalamic view showing thalami (TH) and cavum septi pellucidi (CSP).


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Transventricular view of the atrium, which is marked by calipers and

contains the echogenic choroid plexus (CH).


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Transcerebellar view of the posterior fossa, demonstrating

measurement of the cerebellum (C) and cisterna magna (CM).


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Fetal Measurements

Femur length (FL) - correlates

well with both BPD and

gestational age, has a variation of7 to 11 days in the second

trimester


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Femur Length


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Fetal Measurements

Abdominal circumference (AC) - parameterwith the widest variation of 2 to 3 weeks,involves soft tissue rather than bone and is alsothe parameter most affected by fetal growth

AC- skin line in a transverse view of the fetus atthe level of the fetal stomach and umbilical vein

variability of gestational age estimationincreases as pregnancy advances

third trimester- all individual measurementsbecome less accurate


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Fetal Measurements

variability of gestational age

estimation increases as

pregnancy advances

third trimester- all individual

measurements become lessaccurate


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Amnionic Fluid

amount of amnionic fluid

Oligohydramnios - seen as obvious crowding of

the fetus and absence of any significant pockets of

fluid

Polyhydramnios - an apparent excess of fluid

Most widely used is the amnionic fluid index (AFI)

AFI- NV: 8 and 24 cm ( > 24 weeks )

Largest vertical pocket- NV: 2 to 8 cm (< 24 weeks)


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used to measure amniotic fluid

calculated by adding the verticaldepths of the largest pocket in each of

four equal quadrants

Amniotic Fluid Index


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Central Nervous System

Neural-Tube Defects-

second most common class of congenital anomalies

Defects result from incomplete closure of the neural

tube by the sixth week, or the embryonic age of 26 to28 days.

Anencephaly

Cephalocele Spina bifida


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Anencephaly

A lethal defect characterized by the absenceof the brain and cranium above the base of

the skull and orbits


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Anencephaly

can be diagnosed as early as the first trimester

Inability to obtain a view of the biparietal

diameter should raise suspicion

Polyhydramnios from impaired fetal

swallowing is common in the third trimester.


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Anencephaly

the diagnosiscan be made

as early as

12 -13 weeks

Ultrasonography


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Anencephaly (Pregnancy Management)

Prognosis:

* invariably lethal* 50% - stillborn

* 50% - neonatal

death


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Monitoring:

* usual prenatalcare

- emotional support for the family

- assess for polyhydramnios

- tocolysis is NOT indicated


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Delivery:

Vaginal

Special Issues:

Termination

Induction oflabor


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Anencephaly (Neonatology)

Resuscitation:

never indicated

Nursery management:

warmth, hygiene

facilitation of parentalgrief


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Cephalocele

herniation of meninges and brain tissue

through a defect in the cranium, typically an

occipital midline defect


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Spina Bifida

- a neural tubedefect of the

spine in whichthe dorsal

vertebral

arches fail tofuse together


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Spina Bifida

meningocoele


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Spina Bifida

meningomyelocoele


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Spina Bifida

the diagnosiscan be made

as early as

16 -18 weeks

Ultrasonography


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Sagittal (LEFT) and transverse (RIGHT) views of the spine in a fetus with

a large lumbosacral meningomyelocele


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Spina Bifida

Ultrasonography

Transverse


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Frontal scalloping or lemon sign in a fetus with a spinal meningomyelocele


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The banana sign, seen in this fetus with a meningomyelocele, develops when the

cerebellum is bowed and inferiorly displaced, causing effacement of the cisterna

magna

V i l l


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Ventriculomegaly

Enlargement of the cerebral ventricles

The lateral ventricle is commonly measured at its atrium,

which is the confluence of the temporal and occipital horn.

the measurement is relatively constant at 7 mm, with

standard deviation of 1 mm, from 15 weeks onward

Mild ventriculomegaly is diagnosed when the atrial width

measures 10 to 15 mm, and overt ventriculomegaly when it

exceeds 15 mm

A dangling choroid plexuscharacteristically is found in severe

cases

prognosis is determined by both etiology and rate of

progression


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Transventricular view of the atrium, which is marked by calipers and

contains the echogenic choroid plexus (CH).


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The atria appear unusually prominent in this fetus with mild ventriculomegaly

(caliper measurement 12 mm).


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Cystic Hygroma

congenital malformation of the lymphatic

system in which large, often multiseptated,

fluid-filled sacs extend from the posterior neck

usually develop as part of lymphaticobstruction sequence, in which lymph from

the head fails to drain into the jugular vein

and collects instead in jugular lymphatic sacs. Prognosis depends on the karyotype


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Large, septated cystic hygromas in a 17-week fetus with Turner syndrome


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Thorax

four-chamber view of the heart filling

approximately two thirds of the area

lungs are best visualized after 20 to 25 weeks

appear as homogeneous structures

surrounding the heart


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Diaphragmatic Hernia

left-sided and posterior

displacement of the heart to the middle or

right side of the thorax by the stomach and

bowel

absence of the stomach bubble within the

abdomen, small abdominal circumference

bowel peristalsis seen in the fetal chest


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Heart

cardiac malformations are the most common congenitalanomalies

Almost 90 percent of cardiac defects are multifactorial

As many as 30 to 40 percent of cardiac defects diagnosed

prenatally are associated with chromosomal abnormalities

recognition of a cardiac malformation should prompt fetal

karyotyping.

The most frequently encountered aneuploidies are trisomies

21, 18, and 13, and 45, X (Turner syndrome).


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Four-chamber view of the fetal heart, showing the location of the left and right

atria (LA, RA), left and right ventricles (LV, RV), foramen ovale (FO), and

descending thoracic aorta (A).


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Gastrointestinal Tract

stomach is visibleafter 14 weeks

the liver, spleen, gallbladder, and bowel can be

identified in many second- and third-trimester

fetuses

Non-visualization of the stomach within the

abdomen is associated with a number of

abnormalities, such as: diaphragmatic hernia,abdominal wall defects and esophageal atresia


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Transverse sonogram of a second-trimester fetus with an intact anterior

abdominal wall and normal cord insertion.


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Normal Abdominal Wall Development

Physiologic gut herniation:

6th 10th week AOG

Complete closure of the

abdominal wall:

10th 12th week AOG


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Abdominal Wall Defects

Omphalocoele Gastroschisis



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Gastroschisis full-thickness defect in the abdominal wall

Typically it is located to the right of the umbilical cord insertion

bowel herniates into the amnionic cavity

survival rate of at least 90 percent

result from an early vascular occlusion that leads to localizedabdominal wall ischemia.

Omphalocele

abdominal contents covered only by a two-layered sac of amnionand peritoneum.

The umbilical cord inserts into the apex of the sac may occur as part of a genetic syndrome, such as Beckwith

Wiedemann orpentalogy of Cantrell


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In this fetus with gastroschisis, extruded bowel loops are floating in the

amnionic fluid to the right of the normal umbilical cord insertion site (arrow).


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Gastroschisis full-thickness defect in the abdominal wall

Typically it is located to the right of the umbilical cord insertion

bowel herniates into the amnionic cavity

survival rate of at least 90 percent

result from an early vascular occlusion that leads to localizedabdominal wall ischemia.

Omphalocele

abdominal contents covered only by a two-layered sac of amnionand peritoneum.

The umbilical cord inserts into the apex of the sac may occur as part of a genetic syndrome, such as Beckwith

Wiedemann orpentalogy of Cantrell


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Transverse view of the abdomen showing an omphalocele as a large

abdominal wall defect with exteriorized liver covered by a thin membrane.


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G i i l A i


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Gastrointestinal Atresia

Most atresias are characterized by obstructionwith proximal bowel dilatation

the more proximal the obstruction, the more

likely it is to be associated with hydramnios.

Esophageal atresia may be suspected when

the stomach cannot be visualized and

hydramnios is present.

E h l At i


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Esophageal Atresia

D d l i


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Duodenal atresia

so-called double-bubble sign, whichrepresents distention of the stomach and the

first part of the duodenum


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Double-bubble sign of duodenal atresia is seen on this axial abdominal

image of the fetus.

Kid d U i T t


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Kidneys and Urinary Tract

paraspinous masses frequently as early as 14 weeks, and routinely by

18 weeks

The placenta and membranes produce amniotic

fluid early in pregnancy,. but after 18 weeks, mostof the fluid is produced by the fetal kidneys

Fetal urine production increases from 5 mL/hr at20 weeks to about 50 mL/hr at term

Unexplained oligohydramnios suggests a urinarytract abnormality


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Longitudinal sonogram of fetal kidney depicting the hypoechoic medullary

pyramids (M).


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R l A i


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Renal Agenesis

No kidneys are seen ultrasonographically at any point during

gestation.

The adrenal glands typically enlarge and occupy the renal

fossae

Without kidneys, no urine is produced, and the resulting

severe oligohydramnios leads to pulmonary hypoplasia, limb

contractures, a distinctive compressed face, and death from

cord compression or pulmonary hypoplasia.

When this combination of abnormalities results from renal

agenesis, it is called Potter syndrome

When these abnormalities result from scant amnionic fluid of

some other etiology, it is called Potter sequence.


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Urinary Bladder


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Urinary Bladder


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Secondary hydronephrosis from


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bladder outlet obstruction

Three Dimensional Ultrasonography


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Three-Dimensional Ultrasonography

superior views of fetal surface anatomy improved visualization of selected structures such

as the face, ear, and extremities.

to adequately image a fetal structure in three

dimensions, the part must be surrounded byamnionic fluid because crowding by adjacentstructures obscures the captured image.

even under ideal circumstances, image

processing may take considerably more time thanis typically devoted to two-dimensional (2-D)scanning.


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used to determine the volume and rate of blood flowthrough maternal and fetal vessels

Clinical Applications:

systolic

diastolic ratio (S/D ratio) - comparesmaximum (peak) systolic flow with end-diastolic flow,

thereby evaluating downstream impedance to flow

DOPPLER VELOCIMETRY


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Doppler waveforms from normal pregnancy. Shown clockwise are normal waveforms

from the maternal arcuate, uterine, and external iliac arteries, and from the fetal

umbilical artery and descending aorta. Reversed end-diastolic flow velocity is

apparent in the external iliac artery, whereas continuous diastolic flow characterizes

the uterine and arcuate vessels. Finally, note the greatly diminished end-diastolic flow

in the fetal descending aorta.

Umbilical Artery


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Umbilical Artery

This vessel normally has forward flow throughout the cardiaccycle, and the amount of flow during diastole increases as

gestation advances.

Thus the S/D ratio decreases, from about 4.0 at 20 weeks to

2.0 at term. The S/D ratio is generally less than 3.0 after 30 weeks

Umbilical artery Doppler may be a useful adjunct in the

management of pregnancies complicated by fetal growth

restriction. Not recommended for screening of low-risk pregnancies or for

complications other than growth restriction

Umbilical Artery


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Umbilical Artery

ABNORMAL:

ifthe S/D ratio is above the 95th percentile for gestational

age.

In extreme cases of growth restriction, end-diastolic flow

may become absent or even reversed

These are ominous findings and should prompt a

complete fetal evaluationalmost half of cases are due to

fetal aneuploidy or a major anomaly

In the absence of a reversible maternal complication or afetal anomaly, reversed end-diastolic flow suggests severe

fetal circulatory compromise and usually prompts

immediate delivery

Umbilical artery

D l f


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Doppler waveforms:

A. Normal diastolic flow.

B. Absence of end-diastolic

flow.

C. Reversed end-diastolic

flow.

DOPPLER VELOCIMETRY


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DOPPLER VELOCIMETRY

Diminished blood flow may be reflected such asthe ff:

1. Diastolic notch

2. Increased SD ratio (Stuart Index)

3. Pulsatility index; Resistance index

4. Absence or reversed end diastolic (ARED)

blood flow

Ductus Arteriosus


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Ductus Arteriosus

used primarily to monitor fetuses exposed toindomethacin and other nonsteroidal anti-inflammatory agents.

Indomethacin, which is used for tocolysis, causes

constriction of the ductus in sheep and human fetuses The resulting increased pulmonary flow may cause

reactive hypertrophy of the pulmonary arterioles, andeventually pulmonary hypertension develops

this complication is largely reversible if medication isdiscontinued before 32 weeks

Middle Cerebral Artery


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Middle Cerebral Artery

Peak systolic velocity in the middle cerebralartery is increased with fetal anemia because

of increased cardiac output and decreased

blood viscosity The cerebroplacental ratio has been

introduced as an indicator of brain sparing in

fetuses with growth restriction

Uterine Artery


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Uterine Artery

Uterine blood flow increases from 50 mL/minearly in gestation to 500 to 750 mL/min by term

Increased resistance to flow and development of

a diastolicnotch have been associated withpregnancy-induced hypertension

increased impedance of uterine artery

velocimetry at 16 to 20 weeks was predictive of

superimposed preeclampsia developing in

women with chronic hypertension.


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Normal uterine artery waveform with high-velocity diastolic flow.


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Ultrasonography and Doppler 3rd Year Lecture 2012

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