ULTRASOUND 18-20 WEEKS - Normal (MORPHOLOGY SCAN)

 

 

HEAD ULTRASOUND

 

 

fetal Head BPD and Head Circumference
The correct plane for the measurement of the head circumference (HC) and bi-parietal diameter (BPD)must include the cavum septum pellucidum, thallamus and choroid plexus in the atrium of the lateral ventricles. BPD: Measure outer table of the skull to the inner table.
HC: Measure around the outer table of the skull.
 
Posterior Fossa Cerebellum, cisterna magna and nuchal fold
 The correct plane for measuring the nuchal fold is to have cavum septum pellucidum (CSP) and the cerebellar hemispheres in the image.
  • The cerebellar diameter should approximately equal the weeks of gestation. (EG 19weeks=19mm)
  • Normal cisterna magna is less than 10mm.
  • A normal nuchal fold is less than 6mm (between 17-20weeks).
 

  
Choroids and lateral ventricles Profile
The LATERAL VENTRICLES should be less than 10mm in diameter (best measured at the occipital horn).
The CHOROID PLEXII should be homogeneous. Small, and sometimes multiple, choroid plexus cysts are a common finding on high resolution equipment. They are of doubtful significance as an isolated finding.
 PROFILE - ensure the mandible is appropriate size, nasal bone is present and there is a normal face/head shape.


 
Orbits Coronal Nose and Lips
FACE: Ensure there is symmetry with a normal inter-orbital distance. NOSE & LIPS: From the 'face' image, rotate the probe to visualise the nose and lips front on.
2 distinctly seperate nodules and in intact hypoechoic upper lip should be seen. 2 distinctly septate nostrils and an intact hypoechoic top lip.
ABDOMINAL ULTRASOUND 
Abdominal Circumference Abdominal Circumference
AC- ABDOMINAL CIRCUMFERENCE
The Abdominal Circumference must include the portal section from the umbilical  vein, the stomach and a true cross section of the spine with 3 ossification centres. It should be circular in shape.

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Situs heart and stomach left side Diaphragm
First, confirm that the organs are correctly sited right vs left.
An axial plane through the chest and upper abdomen shows the heart and stomach on the same side (which has been proven to be the left).
In  a coronal plane, confirm the presence and position of heart, stomach and bladder. Also check the diaphragm.Ensure that there is no herniation of abdominal contents into the thorax.

FETAL KIDNEYS


 

Transverse Kidneys Kidney longitudinal
 
Confirm the presence and position of both kidneys. Be cautious not to mistake the adrenal glands which are quite large. Look for the anechoic renal pelvis. The renal pelvis TS diameter should be less than 5mm.
The kidneys must be measured in a sagittal or coronal plane.  Utilise colour/power doppler to confirm renal arteries and help identify the kidneys in a larger patient.

 

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UMBILICAL CORD                                                                          


Cord insertion and 2 umbilical arteries Male and female Gender
Cord insertion
Ensure the abdominal wall around the cord insertion is intact and that no bowel has herniated into the cord.
Use power doppler to confirm the presence of 2 umbilical arteries forking around the bladder. (Be careful not to slip into a more coronal plane and mistake the iliac arteries.)
There is an obvious penis identified at 18-20 weeks. Shown on the mouseover is the 3 parallel white stripes of the external genitalia of the female vulva.
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FETAL SPINE      


Coronal Spine Spine sagittal

CORONAL SPINE

Check for any scoliosis.

Cervico-thoracic spine:Check the ribs for symmetry.

Lumbar/sacral spine: In coronal, visualise the sacral taper and pelvic bones.

SAGITTAL SPINE

 Ensure there is a uniform, intact posterior skin edge.
  
Transverse Spine

TRANSVERSE SPINE

The 3 ossification centres of the spine should be visible from neck to the lumbo-sacral junction. A smooth intact skin line should be visible throughout.
Beware overlying cord mimicking a meningocoele.

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FETAL LIMBS

Femur length femur measurement

Femur  Length

The Femur length should only be measured when the femur is horizontal (beam is perpendicular) and shadows evenly- at least from both ends.
 
tibia and fibula foot perpendicular to the lower leg
Lower limbs
Confirm the presence and equal size of the tibia and fibula bilaterally.
The foot should not be seen. A rounded base at the base of the leg when seen front on. If you can see the tibia, fibula and foot in one plane, suspect talipes. Rotate 90degrees to see the sole of the foot and the toes.
The foot should be perpendicular to the tibia and fibula.


Arms Hand ultrasound
Upper limbs
Similar to the leg, confirm the presence and size of length of the 3 long bones in each arm.
The fist is often clenched. Ideally watch the hand open/close and check for 5 fingers/knuckles on each side.Check for the presence of the 5th middle phalanx.

 

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CERVIX

The cervix must be measured from the internal os to the external os.

Cervix Length
The echogenic mucous plug is readily visible in the cervix.
Measure the length of the cervix. It should be at least 30mm, and contain no fluid.

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PLACENTA

 

 

Placenta Placenta to Cervix measurement
Placental bed
  • Locate the placenta (anterior V's posteror or lateral)
  • Ensure there is a myometrial rim of 3mm or more under the placenta (otherwise suspect placenta percreta/accreta).

The placenta tip must be greater than 3cm from the internal os.

 
Placental Contraction
Uterine contraction
Beware of uterine contractions mimicking a low lying placenta.
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For uterine artery assessmentl

 

 

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2nd TRIMESTER ULTRASOUND PROTOCOL

 

ROLE OF ULTRASOUND

In the 2nd trimester, ultrasound is essential for assessing the

  • Current viability
  • Structural integrity of the foetus
  • Placental position and condition

 

This scan must not be done before 18weeks.

19weeks is optimal.

 

Patient History

 

  • Gravidity
  • Parity (Miscarriage, T.O.P)
  • Fertility treatment
  • Date of Last Menstrual Period
  • Current pregnancy History
  • Past pregnancy History (eg gestational diabetes)
  • Gynaecological History
EQUIPMENT SELECTION AND TECHNIQUE
  • Modern ultrasound unit
  • Curved linear probe approx 3-7 MHz depending upon maternal factors
  • Ensure patient comfort and privacy.
  • Warm gel, clean towels
  • Select "Obstetric" preset for appropriate power levels and measurement packages

Use a curvilinear probe (3.5-6MHZ) with low power to reduce risk of bio effects.

SCANNING TECHNIQUE

PATIENT PREPARATION
2 hours before the appointment time, empty your bladder. Over the next hour, drink at least 1 litre of water and do not go to the toilet until instructed.

TIPS AND PITFALLS
  • Ensure the patient presents with a full bladder. This will aid in the cervical measurement and placental position and measurement in relation to the cervix.
  • Do not panic. If you do, you will be adding on another 30minutes to the scan time as you and mother get flustered.
  • Wait till the baby moves into the required position,do not take short cuts.
  • You may even have to bring the Mother in and out of the room 5 times or the next day if after a walk and something sweet to eat the baby still does not cooperate.That is okay!
  • Remember you will need to heel and toe the probe to get the correct plane
  • Roll the patient and scan them decubitus if it helps
  • Start from the cervix then placenta then baby head,heart,abdomen,limbs and spine as a rough guide
  • Have your worksheet with you and mark off as you go so you will not forget anything.
WHAT TO CHECK

WHEN BABY IS SUPINE

  • Profile,nasal bone,nose/lips,mandible,palate,orbits.
  • Humerus,rad/ulna,hands,fingers
  • Heart,4chamber,LVOT,RVOT,heart beat
  • Chest cavity
  • Cord insertion,2 umb.arteries
  • Bladder, gender

WHEN BABY IS DECUBITUS

  • Head,BPD,HC,CBM,NSF,CM,Ventricles
  • Heart,IVS,LVOT,RVOT
  • Diaphragm,liver,GB,bowel
  • AC measurement,stomach,umbilical vein,
  • Spine coronal,trans
  • FL,femora,tib/fib,feet

WHEN BABY IS LYING PRONE

  • Spine,skin line,sagittal,trans
  • Aortic Arch,Ductal Arch
  • Kidneys,long and trans,PUJ
  • Diaphragm
  • Head,choroids
    CERVIX
  • Examine with some fluid in the bladder. Perform a transvaginal scan if it is shorter than 30mm or if Vasa Previa is suspected.
  • Previous Caesar scar and myometrial thickness
    PLACENTA
  • Anterior,posterior,fundal or lateral
  • Placental praevia (or low lying if less than 2cm from internal os))
  • Cord insertion
  • Fibroids
    OTHER
  • Maternal adnexae
  • Maternal kidneys if mother has had pain there
  • Maternal Gallbladder if mother has had RUQ pain.

 

IMAGES TO CHECK GROWTH

Biparietal Diameter and Head Circumference (BPD AND HC):

The foetal head measurement must be taken in a cross sectional approach to include the skull, thalamus,septum pellucidum and it must be symmetrical.The foetus's head should be imaged laterally through the parietal bone.The measurement is from the outer edge to the inner edge of the cranium .

**Note: The cerebellum must NEVER be seen in this image or the probe is too caudal which can give an inaccurate size of the foetal head.

Abdominal Circumference (AC):

The abdominal circumference is taken with a transverse image to include the stomach, portal vein and the spine in a true tranverse plane. The ribs may or may not be seen but must be symmetrical if included.It should be a circle at 18-20 weeks and no compression by external forces.It is best taken with the baby supine or lateral because if the baby is prone then the rib shadows make it difficult to check the correct level.The measurement must be taken around the waist on the edge of the skin layer.

**Note: The kidneys should not be seen in the AC image or the plane is too caudal.

Femur Length (FL):

The femur bone must only be imaged when it is parallel to the probe as it will not be foreshortened. The lateral edge of the shaft is measured from the greater trochanter to the lateral femoral condyle.

**Note: Do not take the measurement if the femur is oblique. It can be underestimated if the medial edge is measured on the deeper femur.

www.obstetricassistant.com

MOST COMMON ABNORMALITIES TO LOOK FOR WHEN IMAGING THE FOLLOWING STRUCTURES

Profile,nasal bone,nose/lips,mandible,palate,orbits.

  • Cleft lip and palate
  • Cystic hygroma
  • Exophthalamus
  • Proptosis
  • Prominent eyes
  • Hypertelorism
  • Hypotelorism
  • Microphthalmia
  • Anophthalmia
  • Facial asymmetry
  • Macroglossia
  • Micrognathia
  • Nasal bone absence or hypoplastic
  • Head,BPD,HC,CBM,NSF,CM,Ventricles
  • Choroids plexus cysts(CPC)
  • Agenesis of the corpus callosumSee embryology
  • Dandy-Walker cyst
  • Echogenic brain focus or foci
  • Encephalocele
  • Holoprosencephaly
  • Intracranial cyst
  • Clover leaf skull
  • Macrocephaly
  • Microcephaly
  • Ventriculomegally
  • Arnold chiari malformation
  • Dandy-Walker malformation
  • Arachnoid cysts
  • Intracranial bleed
  • Posterior fossa cyst
  • Vein of Galen aneurysm
  • Anencephaly
  • Aqueductal stenosis
  • Intracranial teratomas

Heart,4chamber,LVOT,RVOT,heart beat

  • Bradycardia
  • Tachycardia
  • Heart axis towards the left
  • Enlarged heart
  • Ventricular septal defect (VSD)
  • Atrial septal defect (ASD)
  • Coarctation of the aorta
  • Double outlet right ventricle
  • Hypoplastic left heart syndrome
  • Hypoplastic right heart syndrome
  • Single ventricle
  • Tetralogy of Fallot
  • Cardiac rhabdomyoma
  • Ebstein's anomaly
  • Endocardial cushion defect (atrioventricular canal)
  • Ectopia cordis (pentralogy of Cantrell)
  • Common arterial truncus
  • Premature atrial contractions
  • Transposition of the great arteries
  • Bright echoes in the heart
  • Left/right heart enlargement
  • Right atrial enlargement
  • Pericardial effusion
  • Small chest
  • Pleural effusion

Chest cavity

  • Pericardial effusion
  • Small chest
  • Enlarged heart
  • Pleural effusion
  • Cystic masses
  • Cystadenomatoid malformations
  • Diaphragmatic hernia
  • Chest wall haematoma
  • Pericardial cyst
  • Tracheal atresia
  • Mediastinal teratoma
  • haemothorax
    Diaphragm,liver,GB,bowel
  • Diaphragmatic hernia
  • Anal atresia
  • Duodenal atresia
  • Gastrointestinal atresia or stenosis
  • Gastroschisis
  • Omphalocele
  • Meconium cyst
  • Meconium ileus
  • Umbilical hernia
  • Tracheooesophageal atresia or fistula/oesophageal atresia
  • Ascites
  • Midgut volvulus
  • Small bowel atresia
  • Meconium peritonitis
  • Dilated stomach
  • Dilated duodenum
  • Dilated bowel
  • Echogenic mass
  • Adrenal haemorrhage
  • Hepatic tumour
  • Neuroblastoma
  • Ovarian cyst with haemorrhage
  • Echogenic bowel
  • Cystic fibrosis
  • Intragut or intrabdominal bleed
  • Calcification
  • Gallstones
  • Teratoma

Kidneys and Adrenals

  • Hydronephrosis
  • Ectopic ureter
  • Infantile polycystic kidney disease
  • Multicystic dysplastic kidney
  • Posterior urethral valves
  • Reflux (<6mm PUJ)
  • Ureterocele
  • Ectopic ureter
  • Pelvo-uretero junction obstruction
  • Ureterovesicle junction obstruction
  • Horseshoe kidney
  • Pelvic kidney
  • Renal agenesis
  • Ureterocele
  • Adrenal haematoma
  • Adrenal mass

Cord and insertion

  • Omphalocele
  • Gastroschisis
  • Umbilical hernia
  • One umbilical artery

Bladder and Gender

  • Absent bladder
  • Renal agenesis
  • Bladder exostrophy
  • Dilated bladder
    Spine coronal,trans
  • Spina bifida
  • Myelomeningocele
  • Myeloschisis
  • Meningocele
  • Cystic masses
  • Solid masses-Sacrococcygeal teratoma
    Lower limbs
  • Rocker-bottom feet
  • Polydactyly
  • Achondroplasia
  • Achondrogemesis
  • Absent digits
  • Absent limbs
  • Bowing
  • Clinodactyly
  • Club foot
  • Fractures
  • Joint contractures
  • Mesomelic shortness
  • Muscle wasting
  • Rhizomelic shortening
  • Limb shortening

Upper limb

  • Polydactyly
  • Achondroplasia
  • Achondrogemesis
  • Absent digits
  • Absent limbs
  • Abnormal thumb
  • Bowing
  • Clenched hands
  • Clinodactyly
  • Fractures
  • Joint contractures
  • Mesomelic shortness
  • Muscle wasting
  • Radial hypoplasia
  • Rhizomelic shortening
  • Short limbs
  • Limb shortening
IMAGING
  • Do not have your colour scale set too low or 'bleeding' over walls will occur and a small VSD could be missed or a coarctation.
  • Make sure the baby is over 18weeks
  • Dynamic range is narrowed for the heart.

 

 

BASIC HARD COPY IMAGES

 

A morphology series should include the following minimum images: 

  • cervix length
  • placenta
  • placenta to cervix distance
  • BPD
  • HC
  • AC
  • FL
  • REPORT
  • Ventricles and choroids
  • Cerebellum,NF,Cisterna Magna
  • profile
  • nose and lips
  • eyes and orbits
  • palate
  • mandible
  • spine (sagittal,coronal and transverse)
  • pelvis
  • arms, hands, fingers
  • legs,feet,toes
  • diaphragm
  • stomach shown on left side
  • kidneys with PUJ measurement
  • bladder
  • cord insertion
  • 2 umbilical arteries
  • Heart- 4 chamber,LVOT,RVOT,PAV,Aortic arch and ductal arch (in Bmode and colour)
  • heart rate

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