This brief overview of abdominal ultrasound is meant to be just that – an overview. If you are serious about ultrasound, you
will take it upon yourself to review on the ultrasound references in physics such as that by Kremkau. Ultrasound images can
be 100% artifactual, when inappropriate use of the technology is applied. Ultrasound examinations require time and effort
on the part of the sonographer. These types of introductory classes are great for getting an overview, but they are not the
ends of the line for learning how to perform an ultrasound examination. Most abdominal ultrasounds can be performed in 20
to 40 minutes; however, complex studies may require additional time. Ultrasound requires patience and technical expertise
that is only learned after mastering your equipment, the physics of ultrasound and ramifications in identifying abnormal sonographic
anatomy. As you are starting to do ultrasound examinations, read and thoroughly digest Nyland and Mattoon's book on small
animal ultrasound. Find a colleague with the same interest and start a journal club weekly to review this book in depth and
other articles/references that come up. Additionally, start collecting a normal database and scan everything. Look at specifics
(left kidney for 2 to 3 weeks) vs. trying you do a complete study and over 6 months you will start to recognize normal from
abnormal. Be sure to take at least 2 weekend short courses with different instructors each year for 3 years. This is a minimum
investment of 3 years on your part and in order to get "good" at it, you need to practice, practice and practice.
A Tour of the Abdomen
One of the most difficult aspects of abdominal imaging is establishing a set pattern of "exploration", especially compared
with echocardiography, where well established imaging planes are preset. The goal then is to evaluate the heart from these
imaging planes and take specific measurements. In abdominal imaging, conventional windows are not pre-established. Each structure
or organ has a characteristic echogenicity, shape, pattern, location, margin and number. Each organ should be evaluated using
multiple imaging planes. When abnormalities are identified, they should be evaluated in multiple imaging planes. The two most
common methods used for evaluating the abdomen include dorsal or lateral recumbency. I currently use lateral recumbency as
a starting point. HOWEVER, you should learn to use both techniques, as there are advantages and disadvantages of each. You
should be comfortable in doing both. I will roll the dog or cat into dorsal recumbency only when required to evaluate a particular
structure or a possible abnormality more completely. Aspirates and biopsies are done with the animal in the appropriate recumbency
that puts the area of interest the closest to the surface with the least amount of possible structures between the area of
interest and the skin. Abdominal radiographs are still the best way to "survey" the abdomen and should be used as the first
line for evaluating abdominal disorders. Ultrasound can then be used to evaluate specific structures for specific reasons.
The two imaging modalities are in fact complimentary as they provide different information.
Transducer placement and eye-hand coordination takes some practice and getting used to making adjustments while monitoring
the screen. There are three basic movements of the ultrasound transducer that one needs to master. The first is distance motion.
This means that the transducer moves in a cranial or caudal direction and thereby the structures in the image move also in
a cranial or caudal direction. The other distance motions include dorsal and ventral directions and oblique directions. The
second type of transducer motion is non-distance, angular motions. In this case, the transducer stays in the same position
on the animal, but is angled in a cranial, caudal, dorsal or ventral direction. The third type of transducer motion is a rotational
motion whereby the orientation of the beam is redirected from a cranial-caudal orientation to a dorsal-ventral orientation
or an oblique orientation. This type of motion would be one used when moving from a right, parasternal long axis image to
a right, parasternal, short-axis image of the heart. When moving the ultrasound transducer, the motions should be smooth.
Usually you do not have to press very hard wit the probe. Tweaking the transducer can be just as much of an art form with
technical expertise as playing with the ultrasound instrumentation. One should remember that more often than not, one is using
an oblique imaging plane versus a true dorsal, sagittal or transverse imaging plane. On every transducer is a small point
or marker that gives the orientation of the primary ultrasound beam. On the ultrasound screen, there is also a marker that
identifies the mark on the transducer. Place one finger on this marker on the transducer so that you always know the appropriate
image orientation and you do not get lost during the scan.