This is a Sagittal view of an Aneurysm. Again you can see Mural Thrombus both interiorly and posterioly, the indicator is turn towards the head.
This shows the correct measurement and still images of an Aneurysm in both the transverse in a Sagittal view. Note that we're measuring from the outside wall to the outside wall and not simply the Lumen of the Aneursym.
We need to be aware of other fluid filled structures anatomically speaking in the Abdomin. The Gallbladder is encapsulated and should not be mistaken for a vessel.
The IVC is a little bit more difficult. It can be very helpful to look transversely first to identify the IVC on the right of the Aorta and then rotate. But generally the IVC will be thinner walled. It will show respiratory variation that looks like pulsations. However, color flow would not show an Aortic character to those pulsations.
This is a Subcostal sagittal or long axis view showing the IVC draining from the feet into the right Atrium. You can see that the indicator is towards the patient's head and the heart is superior. You can also sometimes see the cephalic veins draining into the IVC as we follow it into the right Atrium.
These 2 clips show the Intra-organic Cava on the left, very plethoric or diluted great within 2 centimeters without respiratory collapse. Whereas the clip on the right shows a complete collapse of the IVC consistent with a fluid lost or dehydration.
The one on the left shows fluid overload and this can be helpful to qualitatively assess the fluid status of the patient. This clip shows a patient that actually had a descending Aortic dissection or flat which is something that sonography fairly specific to pick up but not sensitive to rule out. If you wanted to rule it out you should get a Contrast Enhanced CT Scan.