Advances in Ultrasonography

Not knowing why your beloved pet is sick can be frustrating and heartbreaking, but advances in technology and testing have greatly improved patient care. An ultrasound can be a helpful diagnostic tool when trying to determine the cause of a pet’s medical condition. This was the case with Lizzy, an unforgettable eight-year-old Labrador retriever. Her owner was concerned because her once happy dog was now lethargic, not eating well, panting, and losing weight. We ran blood work, tested her urine, and took x-rays. It wasn’t until we performed an abdominal ultrasound that the problem was discovered; Lizzy had cancer in her spleen. The resulting surgery allowed her to regain her joyful spirit. Lizzy’s case serves as an example of how ultrasonography can help diagnose medical problems when other tests are inconclusive.

ULTRASOUND 101

Ultrasonography, also referred to as ultrasound or sonography, is the use of high-frequency sound waves to generate an image of your pet’s soft tissues. The use of sound waves provides a noninvasive, safe means of obtaining important medical information. In certain circumstances, an ultrasound may provide veterinarians with more detailed information than an x-ray (also called a radiograph), another valuable diagnostic tool that veterinarians use on a regular basis, can provide. The primary advantage of an ultrasound exam is that it allows veterinarians to see the internal appearance of an organ. Ultrasound exams are often performed in conjunction with x-rays.

PRACTICING SOUND MEDICINE

Types of Ultrasounds

An ultrasound may have a different name or purpose depending on what part of the body is being examined:

• Echocardiograms are ultrasounds of the heart that allow veterinarians to evaluate each of the heart’s chambers and all of its valves. Echocardiograms can provide images of tumors as well as any accumulated fluids around the heart. They can also provide a cross-sectional view of the heart, measuring the heart’s wall thickness and chamber size and ultimately showing how well the heart is working.

• Abdominal ultrasounds are the most common type of study performed. They can show any change in size, shape, texture, or internal architecture of the abdominal organs (e.g., liver, intestines, kidneys). This type of ultrasound can help pinpoint areas of inflammation or distinguish cancer from benign cysts (although a tissue sample is generally needed to confirm the diagnosis). An abdominal scan can safely determine a pregnancy starting at around 28 days’ gestation; x-rays require 42 to 45 days’ gestation. (X-rays are, however, more accurate in determining the number of fetuses present.)

• Eye and orbit ultrasounds are of greatest value when direct visualization of the eye is not possible because of an existing disease. Both the eyes’ internal structures and the soft tissues behind the eyes can be inspected using ultrasound. Ailments commonly diagnosed with orbit ultrasounds include retinal detachments, cancers, infections, and foreign objects.

Unfortunately, ultrasonography can’t be used to examine all body structures. Ultrasounds are often not useful for examining the lungs and boney structures. The abrupt change in tissue density from soft tissues to bone or gas causes all the sound waves to be reflected back to the transducer (see the box “How Ultrasonography Works”), producing an unreadable area on the monitor.

A Helpful Tool

Technology and software improvements have advanced the clarity of imaging, aiding veterinarians in their ability to diagnose disease. The twodimensional images generated by standard ultrasonography can now be seen in three dimensions. Special ultrasound units can be used to treat some cancers by heating the cancer cells until they die. Contrast medium, an oral or vascular agent that makes an organ more visible during imaging, is becoming more regularly used and can help veterinarians detect subtle changes in the ultrasound image.

Ultrasound is a painless, safe method of diagnosing a range of medical conditions.

Available on most ultrasound units, Doppler allows veterinarians to look at the speed, direction, and character of blood flow in a specific area. It is commonly used in echocardiograms to evaluate heart murmurs, which are caused by blood moving in the wrong direction through the heart. Doppler is also used in abdominal ultrasounds to help locate irregular vessels and determine the volume of blood flow to an organ or mass.

Ultrasound provides a wealth of information about your pet’s health.

Ultrasounds give your veterinarian more information about your pet’s condition but may not always be able to provide a final diagnosis; additional information from fluid or tissue samples may be needed. By facilitating sample collection without surgery and sometimes without sedation, ultrasound is useful in this way as well.

WHAT TO EXPECT

 Depending on your veterinarian’s experience and the nature of your pet’s illness, many ultrasound exams can be performed by your veterinarian. However, he or she may also want to refer you to a specialist, such as a board-certified veterinary radiologist, cardiologist, or internal medicine specialist, who has advanced training in that discipline. Before the ultrasound examination, your veterinarian will likely want to take x-rays of the region of interest. These can provide useful information in determining what type of exam to perform and on which areas to focus.

Most ultrasound exams are performed without sedation with your pet lying comfortably on her back or side. To provide the veterinarian with a smooth, workable surface, hair may be shaved from the area of interest and gel applied to the skin to help the handheld probe, or transducer, move smoothly and obtain the clearest images. You may also be asked to withhold food or prevent your pet from urinating before the examination to improve visualization of abdominal organs. Most ultrasound studies take about 30 to 45 minutes and are well tolerated by most pets.

Ultrasonography has become a common diagnostic tool used by veterinarians. This safe and painless imaging technique provides a wealth of information about your pet’s health, and as technology improves, so does the ability to detect and treat disease. If you think your pet may benefit from ultrasonography or you have a question about ultrasound technology, ask your veterinarian.

HOW ULTRASONOGRAPHY WORKS

Although ultrasonography was first used in human medicine in the early 1940s, it wasn’t until the early 1980s that the same technology was applied to small animals in veterinary practice.Today, ultrasounds have become a common tool in both human and veterinary medicine, but how exactly does ultrasonography work?

An electrical impulse is sent from the ultrasound unit to a handheld device called a transducer; the transducer allows the veterinarian to direct sound waves to the desired location.The sound waves, which are above the human audible limit, bounce off the structures in their path, and some of the waves return to the transducer.These returning sound waves are called echoes.The echoes are converted back into electrical signals, which are used to generate the image seen on the monitor. All of this happens in a fraction of a second, allowing plenty of time for the process to be repeated and for a moving, real-time image to be generated.