Obtaining the subcostal IVC view:
The transducer is placed longitudinally in the epigastrium or sub xiphoid position. The transducer marker faces cephalad. Fan probe laterally to view the IVC draining and identify it draining into the right atrium.
You may also start with subcostal 4 chamber view, place right atrium in center of screen and rotate probe 90 degrees clockwise to find IVC.
This view is useful for determining intravascular volume status by determining IVC caliber and variation of IVC diameter with respiration.
Image : Normal Respiratory Variation of IVC Caliber. Note the change in diameter of IVC during the respiratory cycle.
| IVC Diameter cm | % Collapse on Inspiration | CVP mmHg |
| < 2 | > 50% | 0 – 5 |
| > 2 | > 50% | 5 – 10 |
| > 2 | < 50% | 10 – 15 |
| > 2 | Minimal | 15 – 20 |
| > 2 + Dilated Hepatic Veins | None | > 20 |
Pitfalls
Confusing or mistaking the upper abdominal aorta for the IVC.
The abdominal aorta has the following sonographic features that distinguish it from the IVC:
(i) thick muscular walls;
(ii) never collapses;
(iii) lies between the spine posteriorly and the liver anteriorly; and
(iv) has pulsatility.
In contrast to the upper abdominal aorta, the upper IVC has the following sonographic features:
(i) thin walls;
(ii) capable of collapsing;
(iii) usually shows no pulsatility (except in patients with severe tricuspid regurgitation); and
(iv) has liver anteriorly & posteriorly to it.
Some of the features are occasionally more difficult to appreciate, so looking for multiple of these datapoints is more useful than fixating on one.