Fetal ductus venosus flow assessment

Fetal ductus venosus flow assessmentcan be sonographically assessed in a number of situations in fetal ultrasound:

• first trimester screening for aneuploidic anomalies
• second trimester scanning when there are concerns regarding
  • intrauterine growth restriction (IUGR)
  • fetal cardiac compromise

Of all the pre-cardial veins, the ductus venosus allows the most accurate interpretation of fetal cardiac function as well as myocardial haemodynamics ⁹.

Radiographic assessment

Ultrasound

Technique

• the fetus should be as still as possible
• the probe is ideally focused so sampling is done where the umbilical vein joins the ductus venosus 
•  a right ventral mid-sagittal view of the fetal trunk should be obtained and color flow mapping used to demonstrate the umbilical vein, ductus venosus and fetal heart
• the probe is ideally angled to allow a mid sagittal plane or a transverse oblique plane through the fetal abdomen
• the image should be magnified enough for the fetal thorax and abdomen to occupy the whole screen
• do not contaminate the ductus venosus fromflow with the flow from the fetal inferior vena cava, for this the Doppler sample should be small ( 0.5- 1 mm)
• the fetusinsonationa angle should be as still as possible30°
• the sweep speed should be high (2–3 cm/s) so that the waveforms are spread allowing better assessment of the a-wave 

On Doppler ultrasound the flow in the ductus venosus has a characteristic triphasic waveform where in a normal physiological situation flow should always be in the forward direction ⁷ (i.e. towards the fetal heart).

This triphasic waveform comprises of:

• S wave: corresponds to fetal ventricular systolic contraction and is the highest peak
• D wave: corresponds to fetal early ventricular diastole and is the second highest peak
• A wave (or rather trough): corresponds to fetal atrial contraction and is the lowest point in the wave form albeit still being in the forward direction

See also

• abnormal ductus venosus waveforms
• ductus venosus
• utero-placental flow assessment