Umbilical Cord Complications and Doppler Ultrasound

14	Umbilical Cord Complications and Doppler Ultrasound

The course and structure of the umbilical cord can, in principle, be displayed by gray-scale ultrasonic imaging when there is sufficient amniotic fluid. However, near term or in critical situations this contrast can be limited, and the abdominal wall may not provide good imaging in all pregnant women. In such cases color-coded Doppler of the umbilical vessels makes it possible to find the umbilical cord, especially when it is in an unusual location, for example, looped around the neck (Figs. 14.1, 14.2a, b), the extremities, or ahead of the presenting part.

The number of vessels can be determined by grayscale or color-coded display.

The thickness of the umbilical cord is of great significance, since it is a measure of the more or less abundant supply of Wharton’s jelly. For one thing, a thick umbilical cord is considered to be an indication of sufficient nutrient supply for the fetus, for another the thickness of the umbilical cord can be an indicator of the degree of risk when there are knots or kinks in the umbilical cord, since a thick cord is hardly in danger of compression.

Color-coded Doppler ultrasound can also detect knots in the umbilical cord, especially when they need to be distinguished from false knots. Doppler ultrasound is also valuable in the detection of eccentric insertions and vasa previa. Similarly, it may be used to make a definitive diagnosis of intertwining of the umbilical cords of monoamniotic twins.

Fig. 14.1 Triple umbilical cord loop. Transverse cut of neck.

Fig. 14.2 Display of the cord looped around the neck. (a) Horizontal section without color Doppler. (b) Horizontal section with color Doppler.

Doppler Ultrasound Findings when Umbilical Cord Complications Affect Hemodynamics

As a rule the unusual findings in the umbilical cord described above do not pose an acute problem at the time of diagnosis. In individual cases, however, spectral or color Doppler sonography may detect a hemodynamic dysfunction by a reduced flow in the umbilical v. or aa. Umbilical cord knots may show a reflection phenomena in the arteries, i. e., the usually smooth waveform of the sonogram of the umbilical aa. shows a notch ig. 14.3). A constriction of the lumen of the umbilical can be seen as a considerable increase in the flow rate and a consequent localized color shift that may extend to aliasing in the color Doppler image.

Fig. 14.3 Late systolic notch on the waveform of the umbilical a., possibly caused by a knot in the umbilical cord.

Table 14.1 Elucidation of umbilical cord findings by various ultrasound procedures

Umbilical cord finding	Ultrasound procedures suitable for displaying finding
Localization	Gray-scale B-mode image/color Doppler ultrasound
Number of perfused vessels	Color Doppler ultrasound
Thickness of umbilical cord	Gray-scale B-mode image
Flow restriction	Doppler sonogram (waveform)/color Doppler ultrasound

Obstetric Applications of Doppler Ultrasound: References

Diagnostic Doppler Ultrasound in Preeclampsia, Eclampsia, and HELLP Syndrome

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