Ultrasonography and radiography are the two most popular imaging modalities in veterinary medicine, and each has its pros and cons. In some cases, both ultrasound and radiography are used to evaluate a patient; they should be considered complimentary imaging modalities.
Radiographs provide a snapshot of large areas of an animal’s body. Digital Radiography (DR) offers superior images of bones, the lungs, and gas-filled organs such as the gastrointestinal tract.
Ultrasound enables veterinarians to evaluate the detailed internal architecture of organs. When diagnosing conditions related to the heart, soft tissues, fluid build-up, and parenchymal disease of organs, ultrasonography is far more useful and accurate than radiography.
So what are the four conditions that are more accurately diagnosed using ultrasound vs. DR?
- Detection of Abnormal Fluid Accumulation
- Abnormal Abdominal Organs
- Heart Disease
- Soft Tissues of the Musculoskeletal System
1. Detection of Abnormal Fluid Accumulation
Because soft tissues and fluids have the same radiographic density, radiography isn’t able to resolve them as different entities. However, fluid is easily recognized with ultrasound, distinguishing it from solid soft tissues structures such as the liver or spleen.
While the presence of fluid greatly diminishes the value of radiographic images, there is an old ultrasound adage: “fluid is your friend”. This is true because the presence of fluid allows superb transmission of the ultrasound beam, allowing you to easily see through and beyond the fluid to evaluate deeper positioned organs.
This makes ultrasound an effective modality for diagnosing potential causes of fluid accumulation such as hemoabdomen and pericardial effusion. In situations where fluid can mimic solid tissue structures, Doppler ultrasound can be used to determination structure has a blood supply (tissue) or is more likely a fluid pocket or cyst (no internal blood flow).
2. Abnormal Abdominal Organs
Ultrasound enables veterinarians to examine the internal structure of organs. If a mass is growing within an organ, it may not be readily identifiable on an X-ray unless it distorts the surface of the organ. However, ultrasound images are actually thin slices of an organ (termed cross-sectional imaging), which can be individually examined to identify, measure, and monitor progression or response to therapy.
3. Heart Disease
Cardiac studies, termed echocardiography or ‘echo’ for short, are one of the most common applications of veterinary ultrasound. Echo involves an examination of the cardiac chambers (wall thickness and chamber size), blood flow through the heart, and the function of the heart and valves.
Veterinarians can use radiography to identify an enlarged heart, but they will not know if the walls of the heart are weak and thin with big chambers (dilated cardiomyopathy), or the walls are thick with narrowed chambers (hypertrophic cardiomyopathy), or there is a build-up of fluid around the heart (pericardial effusion).
Ultrasound provides these details, which help DVMs diagnose certain heart diseases in time to provide life-saving treatment. Doppler ultrasound plays a major role in cardiac assessment and certain calculations packages give measurements used to benchmark disease states for monitoring over time.
4. Soft Tissues of the Musculoskeletal System
Ultrasonography provides much more detailed and accurate information when evaluating the soft tissues of the musculoskeletal system compared to radiography. It can detect tears in the ligaments and tendons of various muscles and is phenomenally useful in determining the state of the healing of soft tissue versus radiography.
Ultrasound can also be used to examine joints and bone surfaces. Periarticular osteophytes, as seen with degenerative joint disease, are readily seen using ultrasound. Ultrasound is also commonly used to direct needle sampling of bone pathology seen on radiographs.
Although radiography is the standard imaging modality in veterinary medicine, more veterinarians are investing in ultrasound due to its superior diagnostic capability for certain conditions and complementary role in others.
In addition to offering better clinical results, purchasing ultrasound equipment helps veterinarians increase their revenues by enabling them to administer ultrasonography on-site rather than referring clients to affiliates. DVMs who offer ultrasound can also attract new clients in other specialty niches. Ultrasound also enables veterinarians to recruit new associates and visiting specialists to the practice.