anatomy scan -a systematic approach

Anatomy Scan - A Systematic Approach

DR PRADIP GOSWAMI FRCOG

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Fetal Anatomy Scan

Standardization

• Performance • Documentation• Interpretation and analysis

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Implication for patient management

To speak the same language

TARGETED IMAGING

Rule of 3

Easy to remember “checklist” approach

Systematic method of scanning

A detailed clinical examination of the fetus

Why at all any checklist ?

• Checklist based approach reduces chance of missing• It helps to know when to “stop” scanning• Provides for verifiable audit if anomaly is missed• Easily reproducible and ideal training method

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Anatomy Scans – Segments

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History Survey

Biometry Targeted scanFetal activity

Fetal enviromentReporting

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Patient History

Consanguinity

Number of gravida and

parity and any significant

obstetric history

Details of scan reports, blood

and biochemistry

screening reports

Any significant family history

Maternal medical

conditions, medications

What are the 20 + 2 planes?

• A combination of 2 overview sweeps & 20 planes of the fetus• Each plane relates to a specific fetal section or view• Measurement(s) to be taken* are included• Each plane has a number of structures to be evaluated*• A combination that enable the potential exclusion of 50 abnormal fetal

appearances

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Anatomical area

Plane Description

Overview 1 Sweep 1 Longitudinal head & body for initial orientation

Spine 123

Sagittal complete spine with skin coveringCoronal complete spineCoronal section of body

Head 456

Transventricular plane*Transthalamic plane*Transcerebellar plane*

Thorax 789

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Lungs, 4 chamber view of heartLeft ventricular outflow tract (LVOT)Right ventricular outflow tract (RVOT) & crossover of LVOT3 vessel trachea (3VT) view of heart

The 20 + 2 planes

*Measurement required

The 20 + 2 planes

*Measurement required

Anatomical area

Plane Description

Abdomen 111213

Transverse section of abdomen with stomach & umbilical vein*Transverse section of abdomen at cord insertionTransverse section(s) of left kidney & pelvis, right kidney & pelvis

Pelvis 14 Transverse section of pelvis, bladder, both umbilical arteries

Limbs 151617

Femur diaphysis length*3 bones of both legs, both feet & normal relationships to both legs3 bones of both arms, both hands & normal relationships to both arms

Face 181920

Coronal view of upper lip, nose & nostrilsBoth orbits, both lensesMedian facial profile

Overview 2 Sweep 2 Transverse sweep of body from neck to sacrum, one vertebra at a time

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Sections required

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3

3

4

4

2

2

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BPD – Transthalamic Plane

T – ThalamiC – CSPM – Midline falx

CT

T M

Salomon LJ, et al. Ultrasound Obstet Gynecol. 2011;37(1):116-26.

Cross-sectional view of the fetal head at the level of the thalami

Ideal angle of insonation is 90°to the midline echos

Symmetrical appearance of both hemispheres

Midline falx cerebri broken anteriorly by cavum septi pellucidi and thalamus

No cerebellum visualized

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Biparietal Diameter


Calipers to be placed at the widest part of the skull.

Any of the following method can be used.

Outer edge to inner edge

Inner edge to outer edge

Outer edge to outer edge

Use appropriate reference chart

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Head Circumference


(Occipito frontal diameter to be measured in BPD plane with

calipers placed at outer edges at both the ends)

HC=(BPD + OFD) × 1.62

Directly placing ellipse

around the outer edge of

the skull

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Abdominal Circumference


Transverse section of the fetal abdomen (as circular as possible)

Distal part of Umbilical vein at the level of the portal sinus forming hockey stick bent

Stomach bubble visualized

Kidneys should not be seen

Part of adrenals in the section is accepted

S – StomachU – Umbilical veinP – Portal veinSP – Spine

S U

P

SP

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AC Measurement

APAD – Anteroposterior abdominal diameter; TAD – Transverse abdominal diameterSalomon LJ, et al. Ultrasound Obstet Gynecol. 2011;37(1):116-126.

Directly use theellipse of the

machine(place the calipers

at the outer borderof the abdomen)

AC = π (APAD + TAD)/2 =

1.57 (APAD + TAD).

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Femur (Diaphyseal) Length

The longest axis of the ossified

diaphysis is measured

Exclude the epiphysis and the triangular spur which is

an artefact

Angle of insonation

should be at 90 degrees


Cephalic Index (BPD/OFD x 100):

§75-85 – Normal§< 75 – Dolicocephaly§>85 – Brachycephaly

ØSizeØShapeØ IntegrityØDensity

Skull

ØHPEØASPØACC

Head

Transthalmic

Midline FalxThalami

Transventricular

LVCSP

Transcerebellar

CerebellumCM

Measurement of LV, CMBiometry of CC and CV

Spine

Sagittal

ContourSacral taper

Transverse

3 ossificationSkin cover

Coronal

Optional

Counting of vertebraAssessment of conus distance

Right lung

Left lung

Heart

Thorax

Counting ribsThoracic circumference

Lung length

Heart

4 Chamber view

Chambers Valves+crux

Outflow tract

Cross overLVOT+RVOT

3 vessel view

No.+ size arrange align

Sequential segmental approach

Cardiac biometry

Abdomen

Upper

StomachPV, GB

Mid

KidneysSmall bowel

Lower

Bladder Genitalia

Measuring RPD routinely, Assessment of renal length

UL/LLRelation

shape

echogen

Extremeties

Measuring all long bonesCounting fingers/toes

Dont forget to look for the movements at joints

Face

Axial

Orbits

Coronal

PMT, NM

sagittal

Profile signature

Measurement of IOD/BODMeasurment of NB

Location and configuration of ear

Enviroment

Placenta

LocationEchogenicityretroplacenta

Liquor

SDP/AFI

Cord

3VCinsertion

Cervix Myometrium

Adnexa

Pla grading/thicknessAFI @TIFFACord length

Placenta Previa Terminology• complete• partial• marginal• low lying

Placenta previaLow lying < 2cm from internal osNormal

Amniotic Fluid Assessment

AF

objective

MVP/SDP AFI

subjective

What abnormalities should be excluded ?

• The key to the 20+2 planes approach is understanding the importance of knowing what the normal ultrasound appearances are in each plane• This knowledge equates to the exclusion of a range of

abnormal appearances &/or abnormalities, rather than ‘making a diagnosis’• The range of abnormal appearances being sought may differ

depending on local service requirements

20 + 2 planes & abnormal appearancesPlane Area Abnormal appearances (50+IUD) excluded by the correct 20+2 approach

Sweep 1 Anencephaly, Intrauterine death

1-3 Spine Abnormal abdominal situs, left sided diaphragmatic hernia, meningocoele, Open spina bifida, sacral agenesis, sacral coccygeal teratoma,

4-6 Head Alobar holoprosencephaly, banana shaped cerebellum, cystic hygroma, large posterior fossa cyst, lemon shaped skull, occipital encephalocoele, skin oedema, ventriculomegaly

7-10 Thorax AVSD, CPAM, double aortic arch, ectopia cordis, overriding aorta, persistent left vena cava*, right aortic arch, severe aortic stenosis, coarctation & pulmonary stenosis, significant pericardial effusion (>4 mm) & pleural effusion (>4 mm), situs inversus/ambiguous, tetralogy of Fallot, transposition, univentricular heart, VSD (moderate/large)

11-13 Abdomen Ascites, bilateral renal agenesis, duodenal atresia, echogenic bowel*, gastroschisis, omphalocoele, renal pelvic dilatation (>7 mm AP), small/absent stomach

14 Pelvis Cystic renal dysplasia, lower urinary tract obstruction, 2 vessel cord

15-17 Limbs Fixed flexion deformities wrist, severe skeletal dysplasia (some), talipes

18-20 Face Anopthalmia, cataract*, cleft lip, proboscis*, severe micrognathia

* Optional, for local decision as to whether or not included

Anatomy Scan at 18-22 weeks

Objectives of Identification- of non-viable abnormalities- abnormalities with high morbidity and long term handicap- conditions with potential for intra uterine therapy - conditions which will require immediate post natal interventions - Finally reassurance that the baby is apparently normal

Image Documentation

Image document

Still images

electronic Paper prints X- ray films

Real time

CD/DVDesp heart

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As exaustive as possibleAll representative images as per

guiddelines

Reporting Findings• AIM – To communicate findings to caregiver.• In a changing medicolegal scenario one should be very

careful with this legal document and include any one of following –

ØA detailed descriptionØRef of protocol followed eg SFM2013 or ISUOG 2014 etc.

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Good practice to attach disclaimerBut caveats exists (caution)

Suboptimal examination should be highlighted

Suboptimal examination

Equipment

Fetalposition

Maternal habitus

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Appropriate recommendation like serial evaluation,referral for 2nd opinion, referral to center with better expertise and equipment.

Please dont leave only to verbal comminication

Conclusion …….

• Checklist based approach

•A detailed clinical examination of the fetus•Systematic method of scanning•Avoid Suboptimal examination•Be Aware when to refer for 2nd opinion • Documentation (still and avi) of all representative images• Report as per guidelines (ISUOG/SFM etc)

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Thank You

anatomy scan -a systematic approach

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