a) First spot the umbilical vein passing through the fetal abdomen.
b) Switch on the color Doppler function to view the flow of the umbilical vein.
c) Reduce or increase the PRF (pulse repetition frequency) function of the color flow until you spot a prominent but short vessel with MARKED ALIASING (ie: turbulent flow producing a multiple shades in the flow image). This is most likely to be the ductus venosus. Note the location of the vessel, just anterior to the fetal aorta.
d) Now switch on the spectral doppler trace of the vessel. This will give a wavy spectral waveform with 3 waves (d): The S wave, the D wave and the A wave. Note the marked diastolic flow in this waveform. This is diagnostic of a normal Ductus venosus. All images by Joe Antony, MD, using a Toshiba Nemio -XG ultrasound system.
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