Suspect abdominal fluid? Think FAST!

Does Fred have free abdominal fluid? Find out FAST! (Shutterstock/Jaromir Chalabala)Do you have an ultrasound machine in your veterinary practice? Do you see emergency cases? At a recent CVC, Justine Lee, DVM, DACVECC, DABT, told veterinarians not to make the mistake of bypassing your machine to help you definitively detect the presence of free abdominal fluid.

First, a comparison to illustrate the benefit. Let's consider a 30-kg Labrador retriever-we'll call him Fred.

• At least 20 to 25 ml/kg of abdominal fluid must be present to be able to detect it by palpation or ballottement. That's at least 600 ml of fluid in Fred!

• At least 5 to 25 ml/kg of abdominal fluid must be present to be able to detect it by blind abdominocentesis. That's still at least 150 ml of fluid in Fred.

• As little as 2 ml/kg of abdominal fluid can be present to detect it by performing a FAST ultrasonographic examination. That's just 60 ml in Fred.

You can see the benefit. Now how to do it? Lee says the FAST protocol, or focused assessment with sonography for trauma, was developed in human medicine for ER physicians who have had little training in performing an ultrasonographic examination. They needed a shortcut to find critical abnormalities quickly. Lee admits that veterinary specialists, excluding radiologists, are often similarly ill-prepared and have limited ultrasound training themselves.

With the FAST method, you only have to look at four locations and see if you see free fluid-caudal to the xiphoid, cranial to the bladder and then the right- and left-dependent flank. (Get more details on the locations and what to look for here, as there are also rapid ultrasound techniques to look at the thorax.) Lee prefers not to position the patient on its back due to lack of stability in emergent patients (as is depicted in most illustrations of the locations to sonogram), but allows the patient be in whatever position is most comfortable (typically lateral recumbency).

“You should normally never see abdominal effusion,” says Lee. “And when you do, it's very important that you tap it off and look at it in-house to find out what it is.”

Her last plea: Make sure you charge for your FAST ultrasound exam and make sure you document it. After all, you spent years and lots of money learning all the differentials for effusions of any kind. You're worth it!