PRUV is an anatomical variant with a probably underestimated incidence whose detection should prompt a comprehensive examination for the detection of cardiovascular and other fetal anomalies (Krzyżanowski, A, et al, 2019, Chaoui et al, 2014).
Embryology / Types
There are two embryological types of PRUV.
The most common type is the intrahepatic type (about 90% of the cases). Embryologically the right umbilical vein fails to form an anastomosis with the right vitelline vein and the left umbilical vein degenerates. This creates an isolated right umbilical vein which joins the portal system at the level of the sinus venosus and there is a normal ductus venosus. (Krzyżanowski, A, et al, 2019, Weichert, J. et al, 2011).
The second type is the extrahepatic type (about 10% of the cases). Here the PRUV bypasses the liver completely and there is no ductus venosus, since the umbilical vein drains into the right atrium directly.
Do not forget that there can be a PRUV as a fourth vessel in case both umbilical veins remain patent (Weichert, J. et al, 2011).
- Intrahepatic type: Umbilical vein hooks towards the stomach instead of hooking away from it.
- Extrahepatic type: Umbilical vein bypasses the liver.
Complications of diagnosing PRUV
- Exclude any other malformations, especially cardiovascular. (Krzyżanowski, A, et al, 2019).
- Krzyżanowski, A. , Swatowski, D. , Gęca, T. , Kwiatek, M. , Stupak, A. , Woźniak, S. and Kwaśniewska, A. (2019), Prenatal diagnosis of persistent right umbilical vein – Incidence and clinical impact. A prospective study. Aust N Z J Obstet Gynaecol, 59: 77-81. doi:10.1111/ajo.12791
- Chaoui, R., Heling, K. S., & Karl, K. (2014). Ultrasound of the Fetal Veins Part 1: The Intrahepatic Venous System. Ultraschall in Med, 35(3), 208–228. https://doi.org/10.1055/s-0034-1366316
- Weichert, J., Hartge, D., Germer, U., Axt‐Fliedner, R. and Gembruch, U. (2011), Persistent right umbilical vein: a prenatal condition worth mentioning?. Ultrasound Obstet Gynecol, 37: 543-548. doi:10.1002/uog.7764