5.3.2\ Doppler Sampling and

Waveform of the Ductus Venous

Fig. 13.60  Doppler waveform of DV is sampled and measured in this image, and the upward spectrum represents Doppler waveform of ductus venosus

5.3.3\ Doppler Measurement of DV

Scanning Method

The fetal abdomen is scanned transversely or sagittally, but sagittal section is adopted usually. The fetal abdomen is scanned sagittally, then the color imaging function is opened, and the ductus venosus between the intrahepatic umbilical vein and the inferior vena cava will be found out.

Section Structures

The umbilical vein goes upward and backward after it enters the liver and becomes a narrow tubular structure called ductus venosus at the junction when it meets the inferior vena cava. The velocity of ductus venosus is high because of the narrow tubular diameter, so the color of blood flow is very bright (Fig. 13.58). The Doppler waveform of ductus venosus is shown as triphasic waves, peak S represents ventricular systolic phase, peak D represents ventricular early diastolic phase, and trough A represents ventricular late diastolic phase (i.e., atrial systolic phase) (Fig. 13.59).

Measuring Method

Doppler sampling gate is placed in the ductus venosus, and the sampling angle is adjusted to smaller than 60° (best to smaller than 45°).

Clinical Significance

Wave A is in the same direction as wave S and wave D when normal; all the three waves represent blood flow back to the heart. The absence or reverse of A wave is shown in the ductus venosus of fetuses complicated with congenital heart diseases and chromosomal abnormalities. But there is a certain percentage of physiological absence or reverse of A wave in the waveforms of ductus venosus, among those normal fetuses between 10 weeks and 14 weeks of gestation.

Normal Reference Values

During 16 weeks to 41 weeks of gestation, the velocity of the ductus venosus in normal fetuses elevates with the growth of gestational age, but the resistance index decreases with gestational age, while S/D ratio remains constant during pregnancy. There are various reports about the normal reference values, but large sample studies are lacking (Hecher et al. 1994; Ai & Todros 1996; Pei et al. 2005; Ai et al. 2007).