Physiological umbilical herniation – a distinctive sonographic feature in the embryonic stage

Physiological umbilical herniation is a temporary change at the embryonic umbilical cord insertion that can typically be observed during prenatal ultrasound examination between 9 and 10 gestational weeks. As a result of the physiological displacement of significant portions of the midgut into the umbilical coelom, the umbilical cord insertion of the embryo quickly becomes distended. This should not be incorrectly interpreted as an omphalocele in the ultrasound examination.

Physiological umbilical herniation is a normal part of embryonic intestinal development. As the midgut elongates, it forms a ventral U-shaped loop of intestine, the midgut loop, that projects into the remains of the extraembryonic coelom in the proximal part of the umbilical cord at the beginning of the 6th embryonic week. While it is in the umbilical cord, the midgut loop rotates 90 degrees counterclockwise. During the 10th embryonic week, the physiological umbilical hernia resolves in that the intestines return to the abdomen. As the large intestine returns, it undergoes a further rotation of 180° in a counterclockwise direction around the axis of the superior mesenteric artery. The total rotation of the intestine is thus 270 degrees (Moore KL, Persaud TVN, Torchia MG. The developing human, Elsevier 2016).

3 D ultrasound and its different visualization modes (Merz E. 25 years of 3 D ultrasound in prenatal diagnosis (1989 – 2014). Ultraschall in Med 2015; 36: 3 – 8) make it possible to clearly see the distension of the embryonic umbilical cord insertion from outside as well as to identify the loop of intestine within the physiological hernia at 9 – 10 gestational weeks. The HDlive-Studio mode, which can use a total of 3 independent virtual light sources, can be used for surface imaging. This provides a photorealistic image of the embryo with optimal illumination of the surface ([Fig. 1a]). The loop of intestine within the umbilical cord can be visualized with the HDlive-High Silhouette mode which can be used to acquire a transparent image of the fetus as well as the umbilical cord ([Fig. 1b]). A physiological umbilical hernia should no longer be able to be detected on ultrasound by 12 gestational weeks at the latest. However, if clear distension of the fetal umbilical cord insertion can still be seen at this time, this is an early omphalocele requiring further testing.

Fig. 1 a Surface image (HDlive-Studio mode) of an embryo with a physiological umbilical herniation (10 gestational weeks). The distention of the umbilical cord at the embryonic insertion can be clearly seen. b The HDlive-High Silhouette mode allows transparent visualization of an embryo and the umbilical cord insertion so that the midgut loop within the umbilical cord is visible.

Abb. 1 a Oberflächendarstellung (HDlive-Studio-Modus) eines Embryos mit physiologischem Nabelbruch (10 Schwangerschaftswochen). Deutlich erkennbar ist die Auftreibung der Nabelschnur am embryonalen Ansatz. b Der HDlive-High Silhouette-Modus gestattet eine transparente Darstellung des Embryos und des Nabelschnuransatzes, wodurch die Dünndarmschleife innerhalb der Nabelschnur sichtbar wird.