Which Vessel Contains the Most Deoxygenated Blood
The inferior vena cava (IVC) carries the largest volume of deoxygenated blood back to the heart, as it drains blood from the entire lower half of the body including the abdomen, pelvis, and lower extremities. 1, 2, 3
Anatomical and Physiological Basis
The IVC is the largest vein in the human body and serves as the primary conduit for deoxygenated blood returning from all tissues below the diaphragm. 1, 2 This anatomical positioning means it collects venous drainage from:
- Lower extremities (the largest muscle mass in the body)
- Abdominal organs (including liver, kidneys, and gastrointestinal tract)
- Pelvic structures 3
The superior vena cava, while also carrying deoxygenated blood, drains only the upper body (head, neck, arms, and upper thorax), representing a smaller anatomical territory and therefore lower total blood volume. 4
Hemodynamic Considerations
During normal circulation, the IVC delivers this deoxygenated blood (with a PaO₂ of approximately 6 kPa or 45 mm Hg) directly into the right atrium. 4 From there, blood flows through the right ventricle and into the pulmonary artery for oxygenation in the lungs. 5
The oxygen saturation measurements obtained during right heart catheterization routinely include IVC sampling specifically because it represents the largest single source of systemic venous return. 4
Clinical Relevance
The IVC's size and dynamics reflect blood volume status and right atrial pressure, making it a critical diagnostic target in ultrasound assessment of volume status and cardiac function. 2, 6 The vessel's diameter correlates with mean right atrial pressure (r = 0.72, p < 0.001), and its respiratory variation provides information about right ventricular function. 6
In congenital heart disease, particularly single-ventricle physiology, surgical procedures like the Fontan operation specifically redirect IVC blood flow directly to the pulmonary arteries to complete the separation of systemic and pulmonary circulations. 4, 7 This surgical approach underscores the IVC's role as the dominant source of deoxygenated systemic venous return.