Module 8 : Doppler Flashcards
what are the 4 methods of fetal doppler assessment
- continuous wave (non stress test)
- pulsed wave doppler
- colour doppler
- power doppler
what technical parameter needs to be adjusted when doing doppler on baby
- power
what three things are qualitatively analyzed
- low of diastolic flow
- reversal of diastolic flow
- notching of venous flow
what velocities are increase as term approaches and why
- diastolic velocities
- due to decreased placental resistance
why is it called semiquantitave analysis
- difficult to control angle of incidence
- equations are all angle depenedant
what are the three ratios used to asses flow
- pulsatility index PI = (S-d)/mean velocity
- resistance index RI = (S-D)/S
- systole/diastole ration = S/D
what causes and increase of PI
- increase impedance
when will the S/D ratio become infinity
- when diastolic velocity reaches zero
when will the RI become 1
- when diastolic flow is zero
does the PI stay the same
- no it continuous to show change even when diastolic flow is zero
how many waveforms should be measured to reduce error
- 3 or more
when should we avoid performing doppler
- during fetal breathing periods
how does the vascular resistance change during pregnancy
- during embryonic period normal to have high resistance absent end diastolic flow
- near end of 1st trim end diastolic flow appears
- near end of pregnancy end diastolic velocity increases
what fetal vessels are routinely assessed
- umbilical artery
- ductus venosus
- fetal cerebral vessels MCA
- fetal aorta
- umbilical vein
- fetal IVC
how does the PI, RI, S/D ratios change in the UA during pregnancy
- all decrease because diastolic flow increases
where are ratios higher when sampled in the cord
- higher if measured at fetal end of the cord
what are abnormal umbilical artery findings
- decreased or absent diastolic flow causes elevated RI and PI
- reversed diastolic flow indicating severe fetal distress
- RI > 0.72 is abnormal from 26 week onward
what are the indications for umbilical artery doppler
- small for gestational age
- hypertension in pregnancy
- diabetes type 1
- discordant growth in TTS
- poor growth in both twins due to placental insufficiency
what is the normal flow in the umbilical artery
- forward flow through all phases of the cardiac cycle
what is abnormal flow umbilical artery d
- absent diastolic
- reversed diastolic
where is the fetal aorta sampled
- descending aorta just Bove the diaphragm
- appearance is similar to umbilical artery
in which vessel is changes noticed earlier UA or ao
- AO
when is the MCA sampled
- asses for brain sparing effect with IUGR fetuses
- preferential flow to the brain results in an increased diastolic flow during fetal asphyxia
what are the cerebral umbilical ratios
CU ratio = MCA PI/UA PI
- describes the relative impedance to blood flow between maternal and fetal circulation
when is the CU ratio abnormal
MCA PI/ UA PI < 1
how is the MCA doppler affected by immune hydrops
- anemia causes increased systolic velocity due to decreased viscosity of the blood
- > 1m/sec indicates an amnio
how is the MCA sampled
- slightly caudal from BPD
- measure MCA that is closest to tansducer
- must have MCA flow parallel to sound beam
- sample at prox segmento of MCA
why do we need to be conscious of transducer pressure when sampling the MCA
- constant pressure from the transducer can cause a reaction similar to that of fetal distress so the blood will shunt to the brain
- causing abnormal false positive
how is umbilical vein flow changed during pregnancy
- during embryonic period flow is pulsatile
- should not be pulsatile from 2nd trimester on
what doe venous pulsation in the UV indicate for the fetus
- poor prognosis
- CHF
where is the ductus venous located and what si the normal flow
- in fetal liver between left portal vein and IVC
- normal to see continuous biphasic flow
what is abnormal flow in the DV
flow below the baseline
why does the recipient twin in TTTS demonstrate flow below baseline and TR in the DV
- volume overload
- getting too much blood
what is the purpose of ductus venosus
- regulator of oxygen to the fetus
- half of the blood returning from the placenta is directed through the DV
how do we obtain ductus venosus flow
- level of AC
- colo doppler of umbilical vein
- sweep posterior towards fetal spine
- locate a turbulent flow vessel
what are the points of the DV wave
- first peak = PSV
- second peak = rapid filling of ventricles
- A wave = atrial contraction (reversal abnormal)
what is the flow in the IVC
- triphasic close to the heart
- becomes biphasic further from heart
- measure below diaphragm
- PI increase with fetal hypoxia/asphyxia
what are 2 ominous signs for hypoxia in the fetus
- reversed flow in the umbilical artery
- increased diastolic flow in the MCA
what do the abnormal dopplers mean
- indicate placental resistance is rising due to loss of small vessels
- loss of perfusion in placenta
- UV flow is decreased causing hypoxia
when is uterine artery doppler warranted
- is PAPP-A low and abnormal when uterine doppler will be performed later
what is the normal PI in the uterine artery
- PI < 1.2
- notching is abnormal
what are three reasons doppler is perform in gynaecology with EV
- persistent trophoblastic disease
- neoplasia or tumours
- AV fistulas
what is the normal Uterine artery RI
< 0.4
what uterine abnormalities can cause low resistance flow
- endo carcinoma
- uterine leiomyoma
what should we look for with doppler in ovarian torsion
- look for color flow
- spectral doppler performed as well
what are the doppler characteristics of ovarian neoplasia
- RI < 0.4
- PI < 1
- increased diastolic flow
- non specific to whether ovarian mass is bengin or malignant
- corpus luteal doppler may mimic neoplasm flow
what does ovarian doppler vary with
- menstrual cycles
+ increases in P and F decrease during ovulation - ovary with dominant follicle
+ decrease PI and RI reflect decreased vascular impedance and an increase in flow in ovary with dominant follicle - inactive ovary
+ low or absent end diastolic flow - pregnancy
how is the flow different in malignant vs benign ovarian neoplasm
- malignant = central flow
- benign = peripheral flow
what is postpartum ovarian vein thrombophlebitis
- inflammation of vein caused by clot
- rare
- associated with post partum, malignancies, PID
- increased risk of C-section patients
what is Virchows triad
- hyper coagulability in pregnancy
- venous stasis
- vessel damage due to uterus expanding and contracting
which ovarian vein is more common to contain clot adn what will it look like
- right t
- dilated hypoechoci tube lacking color or spectral doppler flow
- asses IVC
what are the DDX of ovarian thrombus
- appendicitis
- fibroids
- nephrolithiasis
- ovarian torsion
- tube-ovarian abscess
what are the cause of pelvic congestion
- unknown
what are the symptoms of pelvic congestion
- chronic dull pelvic ache
- pain ( premenstual, mesntual, postcoital, perineal)
what is pelvic congestion associated with and what exam is gold standard for diagnosis
- lower extremity varies, multiparty
- venogram
