Sometimes, radiographs just don’t show the whole picture…
That’s especially true for analyzing the details of soft tissue structures—especially in the abdomen, but in other parts of the body as well.
Limitations of radiographs
One problem you may run into with radiographs is a “silhouette sign,” which basically means that two areas with a similar opacity border one another in your x-ray views. This makes it difficult to tell where one structure begins and the other ends.
A good example of a silhouette that could cause confusion is when the abdomen is full of fluid. Since fluid is approximately the same opacity as the abdominal organs, they may blend together, making it difficult to evaluate the abdominal structures.
In cases like this, an ultrasound can provide additional information. And, ultrasound has many other uses…
What an ultrasound is especially useful for
Radiographs can provide a lot of valuable information. But, they can’t always provide fine detail about texture, small defects, or other abnormalities of soft tissue structures. That’s especially true if the abnormalities don’t result in a big change in opacity or in organ size.
Therefore, ultrasound is often superior for detecting changes within an organ, especially if the change is small, in the early stages of a disease, or otherwise difficult to view on radiographs.
This may include conditions such as…
Nodules or masses within an organ such as the liver, which aren’t large enough to change the radiographic silhouette/size of the organ.
Pancreatitis or certain other disorders of the pancreas.
Calculi of the urinary bladder that are radiolucent.
Details of the gallbladder, an organ that is often difficult to see on radiographs since it is overshadowed by the liver.
Abnormal blood vessels, such as a portosystemic shunt.
Detailed cardiac evaluation, including diagnosing enlargements, congenital abnormalities, neoplasia, and more.
These are just a few examples—an ultrasound has many uses clinically!
Of course, there are some lesions that are better diagnosed using radiographs rather than ultrasound, especially in areas of the body that don’t transmit sound waves well (such as the lungs).
And, by looking at your x-ray views and ultrasound study together, you’ll get more information than you would with either technique by itself.
So, it’s not a matter of choosing between radiographs and ultrasound—instead, they work very well when used together to see the whole clinical picture.
How to use an ultrasound
It takes some experience to get the hang of directing your ultrasound probe and interpreting the images. Taking a course is often the best and fastest way to become proficient.
However, even though the process of performing an ultrasound study is different from obtaining radiographic views, some of the basic principles of interpretation remain the same for both.
Rely on the same good practices you do when reading a radiograph, such as…
Have a system and evaluate each organ (and spaces between the organs) in an order that works for you. Do it the same way each time, to be sure you don’t miss anything.
Examine cross-sectional images together—meaning views that are 90-degrees apart—of each area of study. An ultrasound, like an x-ray, produces a two-dimensional image. So, you’ll want to move the probe to look at each area at different angles (just like orthogonal views provide a complete picture when taking radiographs).
When in doubt, seek a consultation with a radiologist who can help you interpret your images.
Just like any other part of your clinical skills, ultrasound technique and interpretation will come with time.
After all, they call it clinical “practice” for a reason—practice makes perfect.
But with a little time, you’ll likely see a good ROI on your investment, since you can diagnose in-house rather than referring—and may find your ultrasound very useful if you need more diagnostic information in a pinch.
Ask for a free demo at your hospital to learn more.
Written by: Dr. Tammy Powell, DVM
