One of the most common things I hear from clients calling to schedule with Dr. Elliott, the internal medicine specialist here at Sunstone, is that their primary care vet is recommending an ultrasound as the next step for their pet. Indeed, the ultrasound is one of our most valuable tools for diagnosing the pets we see, but many people are surprised to hear that it is an option and may not know why it can be so useful.
There are several different options for imaging when a pet gets sick. The most common is the X-Ray, which most veterinary practices have located right in their clinic for easy use. Less common are ultrasound, CT and MRI. CT and MRI are considered more advanced imaging and are usually only found in a few specialty practices. Ultrasound machines are more common than CT and MRI, but not every veterinarian is trained to use the machine or feels comfortable interpreting the images, so they may refer their patient to a specialist like Dr. Elliott.
The key to deciding which form of imaging a pet needs lies in where the doctor is trying to look. X-Rays work by sending a beam of radiation through the body at undeveloped film for a very brief moment to create a single image. These pictures are very useful for evaluating bones, lungs and giving a general view of soft tissue structures within the body. Ultrasound, on the other hand, uses sound waves to create images. Very similarly to the echolocation used by bats, the ultrasound machine can interpret how the sound waves bounce back, forming a picture. Air and dense structures like bones bounce back the sound waves, while soft tissue structures like the liver and kidneys let some bounce back and some pass through. Because bones and air don't let waves through at all, ultrasound is not a good tool for looking at/behind bones or within air-filled areas, like the lungs. However, it is excellent for looking within the abdomen.
One of the biggest differences between these types of imaging equipment is that ultrasound produces a live video stream of images as the doctor moves the probe around. This lets the doctor see organs from many different angles, which gives them a lot of detailed information. Sometimes there are visible changes, and being able to see those changes gives us a diagnosis. However, in many cases these changes could happen for a variety of reasons and the only way to tell the cause is to look at the tissue on a cellular level. For these times, Dr. Elliott can use the ultrasound as a guide to take a small sample of the organ in question, which is then looked at with a microscope.
In my two and a half years with Dr. Elliott, I have probably helped with somewhere between 1-2000 ultrasounds, so I have seen firsthand how much information can be gathered with this tool. I have also seen when the answer was found with an X-Ray, or a blood test, or a stethoscope. These are all important tools, with their own strengths and weaknesses, for gathering information to piece together the puzzle of what is happening inside each pet.
Internal Medicine Assistant