OBGYN clinical sonography

sonographic criteria for an optimally filled bladder

1. bladder should indent the uterus, and the uterine contour should be maintained

2. the bladder dome should extend slightly (1-2cm) over the uterine fundus

nulliparous uterus ratio

1:2, 40cc volume, fundus 6-8cm

multiparous uterus measurements

1:3, 80cc volume, fundus up to 10cm

sonographic appearance of endometrium in menstrual phase

single, thin line. Possible complex echoes from fluid/blood. <1mm

sonographic appearance of endometrium in post-menstrual phase

mostly anechoic, 2-4mm

sonographic appearance of endometrium in proliferative phase

three echogenic lines, 5-8mm

sonographic appearance of uterus in secretory phase

thickened, highly echogenic to the myometrium, blurring the three-line appearance with an anechoic halo. 9-14 mm

what type of disinfectant is used for transvaginal transducers?

high level disinfectans gluteraldehyde or OPA solutions. However, the transducer should be manually wiped clean of gel and biofilm first.

which muscles are in the false pelvis

iliacus and psoas

which muscle is in the true pelvis

piriformis

rectouterine pouch/pouch of douglas

posterior to uterus, anterior to rectom. Most common site for fluid that may indicate a normal cycle, ectopic pregnancy, PID, cirrhosis, or ovarian cancer

vesicouterine space/anterior cul-de-sac

anterior to uterus, posterior to bladder, potential site for fluid collection

retropubic space/space of retzius

anterior to bladder, potential site for fluid collection

vaginal fornix

recesses formed by cervix protruding into vagina.

ovary characteristics

9.8cc when menstruating, lower echogenicity than uterus, follicles are small anechoic structures in the cortex

arterial supply to uterus

aorta> common iliac> internal iliac> uterine

arcurate arteries

lateral margins of uterus in broad ligament that penetrate the myometrium circumferentially

radial arteries

extend from arcurate arteries into deeper layers of myometrium

straight arteries

supply basal layer of endometrium

spiral arteries

supply functional layer of endometrium

gravida

total number of pregnancies regardless of outcome

para/parity

summary of a woman’s past pregnancy outcomes

TPAL

way para is expressed, term births, preterm births, abortions, living children

what are we looking for during first trimester ultrasound?

confirm and date a pregnancy, looking for ectopic pregnancy, miscarriage, molar pregnancy, vanishing twins.

what are we looking for during a second trimester ultrasound?

anatomical survey/screening, looking for fetal structure anomalies, heart defects, incompetent cervix, abnormal placenta location

what are we looking for during a third trimester ultrasound?

monitoring growth and fetal wellbeing, looking for fetal positions that may be problematic for delivery, amniotic fluid volume, placental locations, monitoring growth

Biparietal diameter (BPD) and Head circumference (HC)

measured in transverse outer to inner for BPD, outer perimeter not including skin for HC, midline falx, cavum septum pellucidum (CSP), and thalami required

abdominal circumference (AC)

measured in transverse outer perimeter including skin, stomach, spine, umbilical vein curving into portal required. Must include skin line.

femur length (FL)

longitudinal/coronal measurement, long axis of ossified portion of bone, beam perpendicular to axis. Do not include distal epiphysis

crown rump length (CRL)

measured migsagittal, from fetal head to butt

gestational sac

3-plane average, measure mean diameter of the anechoic space in sagittal AP, sagittal length, and transverse width

complete previa

placental entirely covers os

partial previa

placenta partially covers os

marginal previa

edge of placenta is at the margin of the intenal os

low-lying previa

placenta is lower in uterus and edge is near but not covering the os

thermal index <10 weeks

TIs soft tissue index

thermal index >10 weeks

Tib bone index

two questions to complete fetal position assessment when there is transverse lie

1. which side of the mother is the fetal head on?

2. where is the fetal spine located (anterior, posterior, superior/fundal)

Corupus Luteum

provides progesterone until week 10, when placenta takes over. Highly vascular functional cyst, demonstrates a ring of fire

corpus luteum measurements

averages 2cm but can be 5-10cm

what should be visualized with a mean sac diameter (MSD) of 18mm or more

an embryo. absence indicates early pregnancy loss

intradecidual sac sign (IDSS)/ double decidual sac sign (DDSS)

4-4.5 weeks

gestational sac

4.3-5 weeks

yolk sac

5-5.5 weeks

embryo with Fetal heart tracing (FHT)

5.6-6.6 weeks

5-alive rule

if fetal heart tracing not present by 5mm CRL, possible early pregnancy loss

amniotic membrane encloses embryo, yolk sac seen

7-7.6weeks

distinct structural anatomy

8+ weeks

if MSD is >10

must see yolk sac

if MSD >18

must see embryo

when is yolk sac obliterated?

around 14 weeks when amnion fuses with chorion

fetal heart tones <6 weeks

110-115

fetal heart tones at 8 weeks

144-159

fetal heart tones >9 weeks

137-144

what does <90bpm indicate?

embryonic bradycardia

what should CRL be at the end of embryonic period

30-31mm

thickened nuchal translucency associated with?

chromosomal abnormalities or heart defects

overall thermal index with respect to ALARA

<1, preferably <0.7

placenta grade 0

smooth chorionic plate, medium level echoes throughout

placenta grade 1

echogenic areas randomly dispersed in placental substance, subtle indentations of chorionic plate

placenta grade 2

basal echogenic densities, comma-like densities

grade 3 placenta

echospared or fallout areas, irregular densities with acoustic shadowing

single maximum vertical pocket (MVP)

semi-quantitative method of measuring amniotic fluid,one pocket measured AP

amniotic fluid index (AFI)

semi-quantitative method of measuring amniotic fluid. Uterus is divided into 4 quadrants and 4 pockets measured AP. Value of all quadrants added to a total AFI

biophysical fetal monitoring (BPP)

performed in the late 3rd trimester to evaluate fetal wellbeing. Criteria scored with either a 2 or a 0:

1. gross movement: 3 or more body or limb movements

2. tone movement: 1 or more extension and flexion of limb or hand

3. respiration movement AKA practice breathing: 30 seconds of sustained motion

4. fluid: at least 1 pocket of amniotic fluid measuring at least 2cm

nonstress test

additional test based on fetal heart accelerations

4 chamber heart takes up _____ of thorax

1/3

femur length

beam should be perpendicular to long axis of the femur. Measurement should not include distal epiphysis

keys to determining fetal lie

plane of section across maternal abdomen, position of fetal spine, left side structures (stomach), right side structures (gallbladder)

endometrium layers

basal layer, functional layer (shed monthly)

multiparous cervix ratio

1:3

postmenopausal cervix ratio

1:1

menstrual phase

early proliferative/post menstrual phase

proliferative phase

secretory phase

ovary volume premenarche

3cc

ovary volume postmenopausal

5.8cc

advantages of transvaginal transducer

closer view, less attenuation from adipose tissue, able to use higher frequency, pelvic organ morphology and echo texture appreciated better

transvaginal transducer limitations

limited FOV, may miss larger or more superior positioned masses, cleaning and disinfection required, special storage guidelines for disinfected transducers, patient acceptance, made need 2nd person as chaperone.

transabdominal advantages

less invasive, broader FOV for larger pathologies and free fluid, can be used on pediatric patients, standard transducer cleaning is less expensive and time consuming

transabdominal limitations

more attenuation from adipose tissue, lower frequency use/lower resolution, obscure or small pathology missed/not appreciated, less accurate for torsion cases

why does transabdominal require a full bladder?

relocates uterus, non-attenuating pathway, pushes bowel away, provides anatomical and acoustic reference

why is an over full bladder problematic for transabdominal

it can displace the uterus and make it appear longer than it actually is

common uses for transperineal ultrasound

vaginal wall abnormalities, distal cervical abnormalities, pelvic floor diorders, PPROM (obstetric)

qualifying CRL measurement for nuchal translucency measurement

39-84mm

when is midgut herniation normal?

between 8-12 weeks

what is the normal range for amniotic fluid index

5-25

sequence of development from fertilization to implantation

fertilization> zygote> morula> blastocyst> implantation