Vena cava

Inferior vena cava (IVC)

The inferior vena cava (IVC) is the body’s largest vein that provides the back-flow of blood to the heart. This vein contains deoxygenated blood returning from the tissues in the lower part of the body (systemic circulation). The inferior vena cava can be best appreciated from a subcostal view. The IVC can be compressed by surrounding tissues such as tumours obstructing the return of blood leading to congestion. This is called the IVC-Syndrome.

IVC subcostal view
IVC subcostal view

Inferior vena cava diameter

Normal Borderline Dilated
<15mm 15-20mm >20mm


Respiratory collaps

With normal RA pressures the IVC collapses in 80% of cases, >40% (measured at the origin of the hepatic vein). 40% collapse corresponds to a pressure of 8-10mmHg in the IVC. At a collapse of 60-70%, the pressure is usually in the IVC 2-4mmHg. With a collapse <40% of the IVC, the pressures exceed >10mmHg. When the IVC is dilated and does not collapse, IVC the pressures can reach 20-25mmHg.

IVC collaps registered with m-mode
IVC collaps registered with m-mode

RA pressure

RA estimated pressure
Inferior Vena Cava size (mm) IVC collaps (%) Estimation RA pressure (mmHg)
<21 >50 3 (range 0–5)
<21 < 50 8 (range 5–10)
>21 >50 8 (range 5–10)
>21 < 50 15 (range 10- 20)


Flow patterns

Because in most cases the the flow in the IVC is perpendicular to the ultrasound-beam, it can not be measured by Doppler reliably. In stead the flow pattern of the hepatic vein can be recorded. They mark the same signals, although the quality of the latter signal is much better because its flow is parallel to the sound beam.

Hepatic vein flow
Hepatic vein flow

Superior vena cava (SVC)

The superior vena cava contains the deoxygenated blood returning from the tissues in the upper part of the body. The superior vena cava connects into the roof of the right atrium. The superior vena cava can transthoracically not be portrayed properly. Some times it can be visualized supraclavicular, however this is not a default recording. The SVC (the lower part) is easier to visualize with TOE. The SVC can be compressed by tumours obstructing the return of blood leading to congestion, this is called the SVC-syndrome.

Bicaval view
Bicaval view

The information above comes from Last changed on: 11 September 2023.