Limited Obstetric Ultrasound Workshop:

Keep Prenatal Care at the Bedside! USAFP 2016 Annual Meeting – Denver, CO Jennifer Chang, MD Elizabeth Pietralczyk, MD Kevin Sisk, DO Matt Snyder, DO, FAAFP Kirsten Winnie, MD

Agenda 0900: Intro, Ultrasound basics Limited 1st trimester scan 2nd/3rd Trimester scan Antepartum testing, BPP Fetal Biometry 1015:

PRACTICE STATIONS – Block 1 (bathroom breaks)

1100: Cervical length measurements Coding, Documentation; Credentials 1130:

PRACTICE STATIONS – Block 2 (bathroom breaks)

1220: Conclusion; clean up

Objectives  Limited 1st trimester US 

Review criteria for viable IUP

 Limited 2nd/3rd trimester US 

Review indications and components of the exam

 Describe options & indications for antenatal surveillance  Advanced Options:  

Perform basic fetal biometry on live models Learn indications/method for cervical length measurement

Ultrasound Physics

US Physics • Uses sound waves to differentiate types of tissues in the body • Frequency measured in cycles per second (Hertz) • Diagnostic US – Mega-Hertz (MHz)

US Physics • Electrical stimulation applied to crystals in transducer produces sound waves • Sound waves reflect off different mediums and are detected by transducer • Echoes are converted to electrical signals and translated into images

What Happens to Sound?  ABSORPTION – due to heat or friction caused by cell vibration  ATTENUATION – weakens as it moves through different mediums  REFLECTION – sound waves change direction after striking a smooth surface  SCATTER – sound echoes in different direction after striking an irregular surface

Sound Waves • Aided by FLUID • Appears black or “echolucent”

• Reflection affected by: • Gas • Scars • Adhesions • Bone • High BMI

Transducer Orientation and Manipulation

Transducers • Different types based on “footprint”, frequency and task • KEY: Greater number of cycles (MHz) = greater resolution but least amount of penetration • OB ultrasonography: • Transvaginal: 5-7 MHz • Transabdominal: 2-3.5 MHz

Transducers • Knob (or “T”) on one end of the transducer corresponds with dot at top of display • Begin with knob facing: • Cephalad (sagittal plane) or • Patient’s right side (transverse plane)

• By convention, transducer’s knob should only be rotated between those two positions (0 to 270 degrees in counterclockwise fashion)

Display (Transabdominal) Near Field

Far Field

Display (Transvaginal)

Scanning Planes • Ultrasound not confined to just 2 dimensions like CT • Add third dimension by rocking and/or sliding transducer • If in doubt, scan object in 2 planes • Gross movements: sliding motion • Fine tuning: rocking, tilting, rotation

Knobology

US Console

Gain • Volume control to hear the echo signals (sensitivity) – does NOT enhance the signals themselves • Regulates amplification of signals • Able to adjust overall gain (entire display) or just near vs. far fields

Zoom/Magnification • Increases image in designated areas • May reduce resolution due to increase pixel size

Depth • Varies depth for optimal display • Adjusts the field of view – amount of penetration of sound beam available to view • DOES NOT adjust the actual penetration depth • May need to adjust gain when adjusting depth

Freeze • Stops real time motion • Stops and starts data display • Cine loop may be used after freezing image – allows operator to “go back in time” if optimal image was missed

Measurement Controls • Caliper markers allow measurement of structures or graphs • May appear as Xs or dotted lines

Performing Measurements 1. FREEZE image 2. Pressing CALCS 3. Press SELECT to choose desired measurement 4. Press SELECT after placing each X where desired 5. Then SAVE

Ultrasound Modes • M-Mode • Pulsed Doppler • Color Doppler • 2D Ultrasound

M-Mode • Motion mode – useful for fetal heart rate and echocardiography • Measure from one peak to next peak • Gives accurate heart rate in bpm

Pulsed Doppler • Fetal Heart rate • Systolic and diastolic function • Allows mother to hear heart beat! • Safety concerns

Color Doppler • Examination of fluid flow (e.g. blood) • Red vs. blue color indicate movement of fluid towards vs. away from transducer respectively • Transducer must be at less than 60 degrees incidence

Is ultrasound safe in pregnancy?  Overall, YES…but…  Use it judiciously (ALARA: “as low as reasonably achievable”)  Minimize duration of exposure  Avoid scanning “just for fun” or non-medical indications  Concerns with Doppler modes (thermal effects)  Doppler uses higher and more focused acoustic energy  Minimize use, especially earlier in pregnancy

Limited 1st Trimester Ultrasound

Kirsten Winnie, MD Adapted from Matthew Snyder, DO and Jennifer Chang, MD

Indications • Confirm IUP vs. gestational sac • Evaluate for multiple gestations • Fetal cardiac activity • Dating

Components LIMITED:

COMPLETE:

• Uterus (rule in IUP)

Add:

• Must see yolk sac (YS) or embryo • Trans/sag views • Predict EDC • Measure cardiac activity

• Adnexa evaluation • Cul de sac - for ectopic • Evaluate bleeding • Nuchal translucency for aneuploidy screening 3

Who needs a 1st trimester US? • NO: Low-risk, asymptomatic, certain LMP • YES: • Medical indications • Uncertain dates • Aneuploidy screening (Nuchal translucency) • Patient request (often considered standard of care) 4

•ACOG Practice Bulletin 101 (2009): Optimal timing for a single ultrasound examination in the absence of specific indications for a 1st trimester exam is 18–20 weeks of gestation. (Level C, consensus) • Gestational age still fairly accurate (within 10 days) • Allows for anatomic survey

Timing of 1st Trimester US •

Discriminatory Zone – the HCG quant level at which one would expect to identify an IUP • Above 1500-2000 for vaginal • Above 5,000 for abdominal (some use 3-4,000)

•

If HCG quant is above discriminatory zone and no IUP is identified, MUST r/o ectopic – obtain formal US

Patient Prep • Ensure proper indication for ultrasound • Correct patient ID Abdominal (TAUS): Vaginal (TVUS): • Full bladder • Empty bladder • Choose correct transducer • Gel in probe cover, sterile Surgilube • Scan from right side on outside

Confirming IUP • Must visualize gestational sac PLUS fetal pole OR YS • Mean diameter of gestational sac (MSD) = L+W+H • > 16 mm without fetal pole/YS may indicate pregnancy failure • r/o ECTOPIC

Early Pregnancy

Gestational sac Double decidual sign yolk sac

Crown-Rump Length •BEST measurement for dating up to 13 6/7 weeks

Method for estimating due date. Committee Opinion No. 611. American College of Obstetricians and Gynecologists. Obstet Gynecol 2014;124:863–6.

Crown-Rump Length •Do not include yolk sac in CRL measurement •Adding 6.5 to CRL (cm) approximates EGA OR • EGA = 6 weeks + (CRL (mm) in days) • Example: CRL of 16 mm =8 weeks and 2 days (6 weeks + 16 days = 8 weeks and 2 days)

Correct measurements

Incorrect

“True” CRL

Maximal axial length

9

Fetal Cardiac Activity • No FCA with CRL of 4 mm (100 bpm • 10-15 mm CRL (7wks) • HR> 110 bpm

Pregnancy Viability Findings diagnostic of pregnancy failure

- CRL > 7mm and no heartbeat - MSD > 25 and no embryo - No embryo with heartbeat > 2 wk after a scan which showed a gestational sac without a yolk sac - No embryo with heartbeat > 11 days after a scan that showed a gestational sac with a yolk sac

Findings suspicious but not diagnostic for pregnancy failure

-CRL < 7mm and no heartbeat -MSD 16-24 and no embryo -No embryo with heartbeat 7-13 days after a scan showing gestational sac without yolk sac -No embryo with heartbeat 7-10 days after a scan showing gestational sac with a yolk sac -Empty amnion -Enlarged yolk sac (> 7mm) -Small gestational sac in relation to the size of the embryo (10 No embryo when MSD >20

Documentation • Whether obtained abdominally or vaginally, the following information should be obtained and st 1 Trimester US Documentation (example) documented: st trimester vaginal scan for Indication: Limited 1 – Presence or absence of IU gestational sac dating – Identification of an embryo or fetus FetalIntrauterine number Single– Live Pregnancy Presence or absence of fetal at cardiac activity Fetal–cardiac activity measured 167 bpm via Mmode– CRL – Uterine and adnexae evaluation (not done in Avg of 3limited CRL =US) 1.72 mm, consistent with 8 week 1

day gestation Final EDD = consistent with LMP — 8/23/16

Summary: 1st Trimester US •

Empty bladder for TVU

•

Verify IUP and fetal number – scan across completely in both sagittal and transverse plane •

IUP = gestational sac + fetal pole OR yolk sac

•

HCG >1500 + no IUP = r/o ECTOPIC

• CRL to confirm vs change dates •

Calculate FHR (M-mode preferred)

Ultrasound in the Trimester

Kevin Sisk, DO

nd rd 2 /3

Indications for Limited Late Trimester Scan  Fetal presentation and lie  Fetal Cardiac activity  Fetal number (and chorionicity)  Amniotic fluid assessment  Placental appearance & location  Fetal biometry

Stepwise Approach Step 1: Fetal presentation and lie Step 2: Fetal Cardiac activity Step 3: Fetal number (and chorionicity) Step 4: Amniotic fluid assessment Step 5: Placental appearance & location Step 6: Fetal biometry

Timing of Examination  2nd Trimester (14-28 weeks)  Ultrasounds in 2nd trimester: 18-22wks  With limited access: 16-25wks 



16-18wks 

Anatomy survey is more difficult



Especially with portable equipment & obesity

>22wks 

Dating of pregnancy is less precise

Fetal Presentation & Lie Lie: orientation of the fetal spine (or long axis) to the maternal spine

Step 1: Fetal Position & Lie  Longitudinal  spines parallel  Transverse  spines perpendicular  Oblique

Fetal Presentation

Vertex/cephalic or

breech longitudinal lie

Fetal Lie

Fetal head to maternal right or left transverse

Fetal Presentation  Part of the fetus closest to the internal cervical os or maternal pelvic inlet  Cephalic (vertex, sinciput, brow, face)  Breech (complete, frank, footling)  Shoulder  Compound

Fetal Presentation

Step 2: Fetal Cardiac Activity  Essential component early in US evaluation  Easily determined by observing cardiac motion  Can be recorded with:  Cine-loop  M-mode image

Step 3: Determine # of Fetuses  Can be suspected earlier in the exam  Evaluate number of crania with mapping of uterus

Step 4: Amniotic Fluid Assessment  Will discuss in next lecture on antepartum testing  Amniotic Fluid Index (AFI)  Biophysical Profile (BPP)

Step 5: Placenta Localization  Fundal  Anterior  Posterior  Right lateral  Left lateral  Previa

Implantation Abnormalities Placenta Previa  Difficult to definitively diagnose before 3rd trimester  Potential lengthening of lower uterine segment  May be distorted by over-distended bladder or during uterine contraction  If noticed on first or early second trimester US, repeat at about 28 wks - determines delivery method

Placenta Previa

Normal Anatomy - TVUS view -

Complete Placenta Previa

Confounder: Full Bladder

Confounder: Contractions

Placenta Accreta INCRETA: Invasion of myometrium

PERCRETA: Invasion through myometrium to, and possibly through, serosa ACCRETA: Placental villi adherent to myometrium

Vasa Previa Velamentous cord insertion

Step 6: Fetal Biometry  STAY TUNED for later!!!

Antepartum Fetal Surveillance

Kevin Sisk, DO

Antepartum Fetal Surveillance  Non-Stress Test (NST)  Amniotic Fluid Index (AFI)  Single Deepest Pocket (SDP)  Biophysical Profile (BPP)  Modified BPP

Antepartum Fetal Surveillance • Considered an in-utero physical exam reflects CNS integrity • Based on fetal response to hypoxia/acidemia • Used as early as 26-28 wks gestation * The negative predictive value of antepartum testing is not as high with an anomalous fetus, in contrast to a structurally normal fetus

Indications 

Hypertensive Disorders



SLE/Scleroderma



Chronic HTN



Multiple Gestations



Pre-eclampsia



Oligo/Polyhydramnios



Diabetes (A1 & A2)



Previous Fetal Demise



Chronic Renal Dz



IUGR



Antiphospholipid Antibody Syndrome



Decreased Fetal Movement



Post-term Pregnancy (>41 wks)



Hemoglobinopathies



Uncontrolled Hyperthyroidism

Reduced Fetal Movement

Biophysical Profile  Combination of NST with 4 real-time ultrasound observations  2 points given to each normal or present observation  Maximum 30 minute time-frame

Biophysical Profile Normal (+2 pts) Fetal Tone

≥1 episode of active extension with return to flexion of fetal limbs, also includes opening/closing of hand

Gross Body Movements

≥3 distinct body/limb movements within 30 minutes

Fetal Breathing

≥1 episode of rhythmic fetal breathing movements of 30 seconds or more within 30 minutes

Amniotic Fluid Index

1 pocket of AF that measures greater than 2cm (single deepest pocket)

Nonstress Test*

Reactive

* NST may be omitted without compromising test validity if the results of all four ultrasound components of the BPP are normal

Biophysical Profile  NORMAL: composite score of 8 or 10  EQUIVOCAL: score of 6  ABNORMAL: score of ≤4 Regardless of score, oligohydramnios should prompt further evaluation  AFI ≤ 2cm in the single deepest pocket

Biophysical Profile

Amniotic Fluid Volume  Not a stagnant pool  Complete turnover of total volume occurs in about 1 day  Fluid made by fetal kidneys/bladder  Removed by fetal swallowing

Amniotic Fluid Index (AFI)  4-Quadrant Method  Summation of the amniotic fluid depths in each of 4 quadrants  Transducer should be perpendicular to ground  Fluid pocket should not include extremity or cord  Single Deepest Pocket 8 cm pocket represents polyhydramnios

Which AFI method is best?  4-Quadrant AFI measurements increase intervention rates without demonstrating improved outcomes, when compared with the single largest pocket (maximal vertical depth) approach.

Amniotic Fluid Index (AFI)

Amniotic Fluid Index (AFI) Parameters: Normal: 8-20 cm Oligohydramnios: ≤ 5 cm Polyhydramnios: ≥ 25 cm Equivocal: 5-8 cm

Oligohydramnios o Rupture of membranes o Renal abnormalities o o o o

Renal agenesis Bilateral renal obstruction Bilateral renal dysplasia Posterior urethral valves or atresia

o Uteroplacental insufficiency – IUGR o Post-dates o Indomethacin/Motrin use

Polyhydramnios  Idiopathic (60%)  Fetal anomalies/genetic syndromes (19%)  Multiple gestations (7.5%)  Diabetes (5%)  Macrosomia (4%)  Isoimmunization (1.7%)

Amniotic Fluid Index (AFI)

Biophysical Profile  Each of the 5 components of the BPP score do not have equal significance  Fetal breathing, AFI and NST are the most powerful variables

Modified BPP  Components:  NST (short-term indicator of fetal well-being)  AFI (long term indicator of fetal status)  Considered normal if reactive NST and SDP >2cm  NPV 99.9% for fetal demise within 7 days

Fetal Biometry Maj Elizabeth Pietralczyk FMOB

Objectives  Understand components of fetal biometry  Recognize landmarks for accurate measurement  Practice landmark identification on live patient

Components  Biparietal diameter  Head circumference  Abdominal circumference  Femur length

Biparietal diameter Head circumference

http://www.ultrasoundpaedia.com

Biparietal diameter & Head circumference  Landmarks:  Cavum septum pellucidum  Thalamus  Choroid plexus

 Biparietal diameter: measure from outer table of the proximal skull to inner table of the distal skull  Head circumference: ellipse drawn around the outside of the calvarium  Should NOT have cerebellum in view

Biparietal diameter

http://www.ultrasoundpaedia.com

Cerebellum

http://www.ultrasoundpaedia.com

Abdominal circumference

http://www.ultrasoundpaedia.com

Abdominal circumference  Landmarks  Umbilical vein  Portal sinus  Stomach bubble  Cross section of spine with 3 ossification centers

 Ellipse around the outside of the abdomen  Should NOT see any portions of the heart or kidneys

Abdominal circumference

http://www.ultrasoundpaedia.com

Femur Length  Landmarks: Femur in a horizontal position  Do NOT include femoral head or distal epiphysis in measurement

http://www.ultrasoundpaedia.com

Femur length

http://www.ultrasoundpaedia.com

Questions?

PRACTICE STATIONS Block 1: 1015 - 1100

Cervical Length Measurement

Matt Snyder, DO

Indications • Identify/monitor women at risk for preterm birth • History of preterm delivery • History of LEEP or cold-knife-cone surgery • Asymptomatic short cervix (