Madurai, India
Persistent right umbilical vein is a vascular pathology in which the left umbilical vein becomes occluded & the right umbilical vein persists and remains open.
In the normal fetus, the right umbilical vein begins to obliterate around the fourth week of gestation & disappears by the seventh week of gestation. Persistent right umbilical vein does not prevent the formation of ductus venosus & it does not alter the distribution of blood to the fetus.
Causes of persistent right umbilical vein:
1. First trimester folic acid deficiency
2. Specific teratogens such as retinoic acid
3. Early obstruction of the left umbilical vein from external pressure or occlusion.
The ultrasound diagnosis of persistent right umbilical vein is made by the findings observed in the transverse section of the fetal abdomen. The criteria used are:
1. Portal vein curved towards the liver.
2. Fetal gall bladder located medially to the umbilical vein i.e. between the umbilical vein & the stomach.
3. Umbilical vein is abnormally connected to the right portal vein instead of to the left portal vein.
Color doppler is necessary to identify the type of persistent right umbilical vein.
The other associated anomalies include:
1. A single umbilical artery, which is the most common congenital anamoly with persistent right umbilical vein
2. Dextrocardia
3. Right sided descending aorta
4. Gastrointestinal tract malformation
5. Skeletal malformations
6. Cardiac anamolies
7. Urinary Tract malformation.
These are the ultrasound images of a fetus with persistent right umbilical vein: