Abdominal Parallel Vessels on Fetal Ultrasound
Why It Matters
In a normal fetus, the abdominal aorta and inferior vena cava (IVC) are positioned asymmetrically.
The aorta lies slightly to the left of the spine, while the IVC is located anterior and to the right.
When these vessels appear parallel and symmetric, it should raise suspicion for abnormal laterality.
Key Association: Left Atrial Isomerism
Left atrial isomerism (also known as polysplenia syndrome) is often associated with:
- Interrupted IVC with azygos continuation
- Parallel abdominal vessels
- Cardiac conduction abnormalities
- Complex congenital heart disease
The “parallel vessel sign” can be one of the earliest clues.
Clinical Insight
If parallel vessels are identified:
✔ Evaluate the three-vessel trachea (3VT) view
✔ Assess pulmonary venous drainage
✔ Check cardiac position and axis
✔ Examine abdominal situs carefully
Fetal heterotaxy is not just a heart problem —
it is a systemic laterality disorder.
