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Inferior vena cava is normal
Medical expert of the article
Last reviewed: 06.07.2025
The inferior vena cava normally changes its diameter during the respiratory cycle, contracting during inspiration and expanding during expiration: these changes in diameter allow the inferior vena cava to be recognized and differentiated from the aorta. In cross-sections, the inferior vena cava is flat or oval, while the aorta is always round: The inferior vena cava is flatter during inspiration and more oval during expiration, especially during forced inspiration (Valsalva maneuver).
Once the inferior vena cava has been identified, a thorough examination of the hepatic and renal veins and, in some cases, the iliac veins must be performed:
In elderly patients, the aorta may displace the inferior vena cava to the right or lie anterior to it. Very rarely, there may be two inferior vena cavae on either side of the aorta: they may be mistaken for hypoechoic, enlarged lymph nodes. Changes in the diameter of these structures during the respiratory cycle will differentiate the veins from other solid structures.