Help! Where do I start with ultrasound?

Developing a consistent technique with ultrasound

Where do you start your clinical exam? Nose to tail or tail to nose?

If you’re like to vast majority of vets I know, you’ll start at the head end. But as long as you don’t miss anything out, there is no one right way.

How do you know you haven’t missed anything?

You go through a similar process each time.

Ok, there may be the odd distraction, like a huge cat bite abscess on the top of the head, that is just crying out for treatment. But generally, you will still go back and check the WHOLE animal before deciding on the next course of action – next diagnostic steps, owner discussion and expectations, treatment, plan and review.

Is there anything different with an ultrasound exam?

There shouldn’t be, but all too often with imaging, particularly ultrasound, but radiography as well, we get distracted by an abnormality. This abnormal finding may or may not be significant, and might not be the only change. If we do not follow a consistent, repeatable approach, we might miss another glaringly obvious abnormality, if only we would look.

And therein lies the problem with ultrasound.

You cannot see all the organs in front of you at the same time on the screen. You cannot even see the whole organ at one time.  

Only a small slice of tissue, lying directly in front of the probe, around 1mm in thickness is visualised on the ultrasound screen. As the saying goes ‘Seek and you will find’ but how long is it reasonable to seek the right adrenal?

At least with an X-ray if there is a foreign body (FB) present, you can hope that it will be radio-opaque to be easily seen on the film.

If not, there are other specific signs to look for in the abdomen: two populations of small intestine (distended loops of bowel, with concurrent normal bowel) or ileus with a palpable abdominal mass. With perforation we would expect to see increased soft tissue opacity indicating inflammation and extra-luminal gas within the abdomen.

Unfortunately, intra-abdominal gas in ultrasound can be confusing for the inexperienced sonographer. Intra-luminal gas can complicate the image, and unless you put the probe in the exact position over a foreign body in the intestine, it can be easily missed.

Confirmation of a FB within the lumen would lead to a well-defined area of distal acoustic shadowing, coming from the luminal surface.

As in so many instances, we would hope telemedicine may be able to assist us.

Unfortunately, a recent study of telemedicine review of ultrasound images on cases of intestinal obstruction had lower than ideal positive predictive value of 55-70% (Sombrio et al, 2023). While observers could agree when there was no FB present, there was considerable disagreement on those cases with a partial, or complete obstruction.

This means it's mostly down to the attending vet to, not only obtain high quality diagnostic images, but to also assess them fully to avoid missing a diagnosis.

If you would like to know more about how to develop a consistent, repeatable ultrasound exam then get in touch today. We have a number of options to help develop your confidence to improve the service you give to clients.

Complete the form here: https://www.skillvetscan.co.uk/contact

References:

Sombrio MS, Mai W, Buch D, Grotti GC, Luciani MG, Froes TR (2023) Accuracy and reliability of tele-ultrasonography in detecting gastrointestinal obstruction in dogs and cats. Journal of Small Animal Practice https://onlinelibrary.wiley.com/doi/10.1111/jsap.13604