What is an ultrasound?
An ultrasound examination, also known as ultrasonography, is a non-invasive imaging technique that allows internal body structures to be seen by recording echoes or reflections of ultrasonic waves.
Ultrasound allow visualization of soft tissue and fluid filled structures in the body. Because ultrasound waves cannot penetrate gas, it is not useful in evaluating bones or lung tissue and can have limitations with examination of the gastrointestinal tract where gas pockets create artifacts in the image.
What preparation is required?
Anesthesia or sedation is not usually needed for most ultrasound examinations, unless biopsies are to be taken or if a patient is frightened or fractious. The technique is not painful and most patients will lie comfortably on a soft pad while the scan is being performed. The hair coat over the area of interest needs to be clipped, since air trapped in and around the coat will interfere with transmission of ultrasound waves. Alcohol and gel are applied to the surface of the skin to further decrease air artifacts. It is important that the patient is fasted for ~12 hours prior to the scan, unless their age or medical condition makes it unsafe. Fasting decreases the amount of gas in the gastrointestinal tract, which minimizes the interference from air.
When is an ultrasound recommended?
Abdominal ultrasound has become a very important and routine tool in the work up for a variety of different cases. If a physical exam or history raises concern about the structure or function of an organ or system in the abdomen, ultrasound can be used to evaluate the size, location and tissue architecture of the area or organ of interest. A few examples include bladder or kidney stones, a mass or tumor in any organ, gallbladder stones/obstruction/rupture, gastrointestinal tract wall abnormality or obstruction. Ultrasound is very sensitive for finding free fluid in the abdomen, and can be used to examine lymph nodes, adrenal glands and other small structures that cannot be felt on abdominal palpation or seen on x-ray.
Although ultrasound allows safe and non-invasive visualization of internal organs, it isn’t always possible to determine the nature or identity of some changes that are found. This is the case when a mass or ‘tumor’ is found. The appearance and location of a mass structure is not usually enough to definitively identify the mass as a benign process, or something more concerning, such as an abscess or cancer. Therefore, ultrasound is often used as a guide to obtain fine needle or tissue biopsy samples. That way, the placement of the biopsy tool is made more accurate and safer. In most cases, a sedative is required to ensure safety of tissue sample collection and a blood clotting panel may be required in some cases to ensure there is no increased risk of bleeding.
Ultrasound is also useful in evaluating the heart, masses at the periphery of the chest cavity, eyeballs and a variety of other soft tissue applications. Ultrasound can detect pregnancy much earlier than x-rays, and the development of the individual puppies or kittens can be monitored.
Is ultrasound better than x-rays?
Despite the immense value of diagnostic ultrasound in working up a variety of diseases and illnesses, it does not replace radiographs (x-rays). Rather, these imaging modalities are often complementary and will be used together to gain the best understanding of the structure and function of body systems. There are many instances where something that is easily identified on x-ray, can be missed on ultrasound, and vice versa.
Is the technique affordable?
Although the initial cost of a scan may seem high, it has to be equated with the high cost of the equipment, the fact that specialized training is required in order to interpret the images, and a significant amount of time is involved in carrying out the examination.