The IVC on bedside ultrasound

Q: Does IVC size predict fluid responsiveness?

Only weakly, especially in spontaneously breathing patients.

The IVC drains into the right atrium; its size and how much it collapses with a sniff give a rough estimate of right atrial pressure.

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How to scan

Curvilinear or phased-array probe, subxiphoid, longitudinal, just right of midline. Follow the IVC into the right atrium; measure about 2 cm from the junction.

Interpretation (ASE)

IVC < 2.1 cm collapsing > 50% with a sniff → low RA pressure (~3 mmHg). IVC > 2.1 cm collapsing < 50% → high RA pressure (~15 mmHg).

Caveats

Mechanical ventilation, raised abdominal pressure, athletes and severe tricuspid regurgitation all confound it. Use it as one clue, not a verdict.

Real scans

Collapsing IVC in hypovolaemia (clip). The IVC collapses completely with each breath, suggesting low volume status. Best seen in motion. Gillman L, Ball C, Panebianco N, Al-Kadi A, Kirkpatrick A · CC BY 2.0 · source

Plethoric IVC in cardiac tamponade (clip). In tamponade the IVC is large and barely changes with breathing (plethoric). Ben Smith · CC BY 4.0 · source

Normal IVC with respiratory variation (animated) — Normal inferior vena cava that gets visibly smaller and larger with breathing. The right heart is seen at the right of the image. — **Normal IVC with respiratory variation (animated).** Normal inferior vena cava that gets visibly smaller and larger with breathing. The right heart is seen at the right of the image. Tinss · CC BY-SA 4.0 · source

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FAQ

Does IVC size predict fluid responsiveness?

Only weakly, especially in spontaneously breathing patients.

Related guides

Pericardial effusion and tamponade on ultrasoundHow to see a pericardial effusion on bedside echo (subxiphoid and parasternal views) and the ultrasound signs of tamponade. Interactive beating-heart simulator.
Abdominal aortic aneurysm on ultrasoundHow to scan the abdominal aorta at the bedside, how to measure it (outer wall to outer wall), and when it’s an aneurysm. Try the calipers in a live simulator.
The parasternal long axis viewHow to obtain the parasternal long axis (PLAX) echo view, probe position and orientation, and the structures you should identify — with a live beating-heart simulator.

Educational content for learners; follow local protocols and supervision. Simulated images are generated by Sonoduck’s physics model; real images are credited individually.