As you may know, my wife Stephanie Lisciandro, DVM, DACVIM (SAIM), was trained at The Animal Medical Center in the mid 1990s. There she was taught to look at the caudal vena cava and hepatic veins for right-sided volume overload and right-sided congestive heart failure by Dr. Richard “Scotty” Scott. In 2005, we created AFAST and TFAST while Stephanie was working as an internist at a referral practice and then doing mobile ultrasound and consulting. She had little interest in AFAST and TFAST until 2010 when she had enough local referring practices begin asking about AFAST and TFAST.
When I explained to her what we were doing, how we were performing the cxam, the information we were acquiring, and how we recorded on goal-dreicted templates, she suggested we add imaging and characterizing the CVC and hepatic veins. This was far in advance (years) of any other point-of-care ultrasonographers considering such a notion. In fact, we trained the groups out of Canada and Europe on how to image and characterize the CVC. So I give all the credit to Stephanie on making this paradigm change in veterinary medicine. We hope you enjoy this ECC and IM Blog.
Some Clinical Pearls for Imaging the Caudal Vena Cava.
Holding the probe.
The key is holding the probe so your scanning plane cuts through the caudal vena cava (CVC) in its longitudinal scanning plane. Holding the probe with your hand on top rather than like a pencil keeps the scanning plane “true.”
Best for success!
Note that the hand is on top of the probe with the thumb on the marker and the index finger on the other end as shown in A). By doing so, the scanning plane is like the piece of paper in B) and in a longitudinal plane. By holding the probe in this manner, you can fan in a “true” longitudinal plane. Staying “true” to the longitudinal plane will give you a good CVC image.
Likely a fail!
Note that the probe is held like a pencil as shown in A). By doing so, the scanning plane is like the piece of paper in B) and obliqued which will not provide a good image of the CVC .
A final comparative image!
Rocking cranially to get the caudal vena cava.
The image of from the 2nd edition of our textbook, a great resource for you, that may be purchased through Amazon. Note in A) the probe marker is directed far cranially bringing the white line of the diaphragm close to the probe head, close to the near field, as shown in C). In contrast in B), the probe is directed toward the spine, which will be a likely fail for imaging the CVC, because it will bring the stomach and its shadowing through your CVC area of interest. In D the overlay shows you the orientation of the heart chambers relative to the diaphragm. Note the left heart is along the diaphragm and this holds true for all quadrupeds. In contrast, people have the right heart closest to the diaphragm.
Additional Pearls for Imaging the CVC are 1) The CVC is Texas Longhorn away from the cardiac bump, where the heart is opposed to the diaphragm, and 2) increasing depth to find and then follow the column of reverberation artifacts to the diaphragm to locate the CVC.
Quiz – Can You Identify the CVC?
Note the image to the left and then the arrows showing the possible location of the CVC. Which image is correct (A-D)? Answer at the bottom of the post.
Measuring the CVC Height
Measuring the maximum height (it’s not a diameter, there is no circle shown) and using our chart to categorize as fluid responsive (bounce), fluid starved (flat), or fluid intolerant (FAT). The best manner to find the maximum height is to image the CVC over several seconds because it has respirophasic variation, then freeze and roll the track ball through frames finding its maximum height. Although, keep in mind that the “eyeball characterization” of the CVC trumps the maximum height.
You may use B-mode or M-mode; however, B-mode is usually much easier (unless you are a cardiologist or use M-mode a lot).
Hepatic Venous Distension and the “Tree Trunk Sign”
We have shown and published (Chou et al. 2021) the “Tree Trunk Sign” as 96% specific and 84% sensitive for the presence of right-sided congestive heart failure (R-CHF). In normalcy you do not expect to see hepatic venous branching. This Chou et al. study is available open access and has some interesting, easily readable tables with measurements of the caudal vena cava and presence of gallbladder wall edema.
Watch the Power of the DH Webinar for more information.
Quiz – Answer is D.