Monday, November 15, 2010

How to learn how to ultrasound a dog

I’ve seen a bunch of ultrasound images (still and moving) throughout vet school. Lecturers will flash up a picture and say things like “and that’s what a pyometra looks like on ultrasound.” And what do I see? MASS OF GREY AND BLACK.

[Image source: Imaging 2003;15:72-78.]

Today we had our first lab in which we got to actually handle ultrasound machines. When you’re driving, everything makes a little bit more sense.

The procedure

Take a dog. Sedate it. Put it on its back (padded to stay in place). Slather gel on its belly. Watch as someone who knows what they’re doing shows you how to find the liver, gallbladder, and kidneys with the ultrasound probe.

The liver isn’t so hard: it’s tucked up under the rib cage, so you put your probe at the end of the rib cage, right in the middle of the belly, and look around. The round black circle that is the gallbladder tells you that you’ve found the right spot. The liver is all around the gallbladder, and once you know that, you can see that it is indeed a slightly different color and texture of grey than all the grey around it. Move the probe back and forth along the dog’s belly, following that particular grey texture until it disappears. You have imaged the liver!

The kidneys are a lot harder to find, as they are not so near the surface of the dog’s body, and they don’t have as clear a landmark. When you do find them, they are super cool to look at, though. The liver is a plain mass of grey, but the kidneys have a pattern to them that looks exactly like a kidney looks when you cut it in half in gross anatomy lab. It convinces you that what you’re looking at is for real and not just made-up images on a computer screen.

Try again with the urinary bladder. That’s easy to find, a nice big black circle. You can change its shape by pushing down with the ultrasound probe. As you are being pleased with how easy this is, the radiology resident comes over and asks if you want to try to find the prostate.

The prostate is hard to find, I tell you what. The resident had to find it for me (I held on to the probe while he moved it, so that I could feel where to put it), and when he pointed it out to me, I was like, “That’s a thing? A thing I am supposed to be able to recognize later? It doesn’t look like anything!”

Wipe the gel off the dog. Call someone to give him his reversal agent to counteract the sedative. Wrap him in a warm blanket and cuddle him while he wakes up.

Success! You saw a liver, gallbladder, urinary bladder, and prostate!

The students

There are two labs for the class of 82 students, so this lab had 41 students in it. There were 5-6 students per dog, 6 students in my group; we took turns with the probe. The dogs were sedated for about 80 minutes, which didn’t feel too long to me.

The instructors

The instructors included: a private practice veterinarian; two radiology residents; a representative of the ultrasound equipment company (who may or may not have been a vet, I wasn’t clear, but certainly knew how to ultrasound a dog).

The equipment

A manufacturer of ultrasound equipment lent us the equipment for the day, so that we could have several ultrasound machines in use at once. They did this out of the kindness of their hearts, and perhaps with the idea that we would think well of them and perhaps purchase some of their equipment some day.

The dogs

The dogs came from my school’s teaching colony. These are ex-research dogs. The research laboratories can’t place the dogs directly in homes once their stint as research animals is over, so they give them to my school, which socializes them for a few years and uses them in procedure labs like this one, then adopts them out. They retire to pet homes for the rest of their lives. I also learned how to do a neurology and cardiology exam on these dogs, among other non-invasive procedures.

The dogs represent a complex moral question for me. Is it acceptable to use them like this? They are cared for well, but they live in kennels rather than homes, and they do have procedures like this done on them, which while non-invasive must be at least a little stressful. However, my school is doing a good thing by helping them to transition from a research environment to pet homes. And the alternative would be that I would learn ultrasound techniques on patients, animals who were actually sick, and perhaps less able to tolerate my bumbling around. In the end, I like this solution.

So thank you to the dog who let me practice on him (although it was not his choice). Thank you to the people who taught me. Thank you to the company who lent the equipment. It was a good lab.


  1. So you can do the ultrasound with gel on the belly fur, without having to shave it?

  2. No, you definitely have to shave the fur. I should have mentioned -- these dogs came to the students pre-shaved.

  3. Why must the fur be shaved, please. Will areas that are read as probable malignancies turn out to be something far less serious? Is air misinterpreted as tumor? Thank you.

    1. The ultrasound machine needs a smooth, close connection to the skin in order to get a good, clear picture. The clearer the picture, the better the information for the person performing the ultrasound. So the animal gets shaved!

    2. I understand that. The vet doesn't understand that. I asked if there would could be misinterpretations of artifacts as tumors. Thank you.

    3. Artifacts can be hard to interpret, and a good shave will help, but u/s interpretation is just hard and a good shave won't completely fix that. In most situations just seeing something tumor-like on an u/s wouldn't be the last step, though. Diagnosis should involve another step -- the u/s just tells you where to look; to find out what the suspicious thing actually is, you have to do something else too (like stick a needle in it, or perform an endoscopy...)

      Hope that helps. Hard to answer -- every situation is a little different.

    4. Yes. Thank you. I know u/s must be done by an experienced professional, and that interpretation is just that. I wasn't able to find any information, you see, on just what how the fur interfered - hence the comments. I appreciate your having replied.