Ultrasound, computed tomography (CT scan), and magnetic resonance imaging (MRI) are technologies now available on a wide scale in veterinary medicine. When used properly where indicated, these diagnostic modalities can aid in the diagnosis and treatment of many diseases. When used inappropriately, they can add greatly to the overall expense of the diagnostics with little if anything to show for it.

Ultrasound imaging, also called ultrasound scanning or sonography , involves exposing part of the body to high-frequency sound waves to produce images of the inside of the body. Ultrasound exams do not use ionizing radiation (x-rays). Ultrasound can be used to visualize the size, contour and texture of organs (a clue as to how well the organ functions), find masses (tumors or cysts), track blood vessels, analyze heart function, and help obtain samples (biopsies) from organs such as kidneys and liver or tumors in a less invasive manner than exploratory surgery. In my practice, ultrasound has been a huge asset. Our ultrasonographer has had many years of experience and the results have been extremely reliable. With ultrasound, diagnoses have often been reached quicker and actually saved the owner's money in the long run as well as minimizing patient discomfort. However, in inexperienced hands, ultrasound can miss the diagnosis or even result in the wrong diagnosis. The best way to prevent this is either to make sure that the ultrasound is done by a veterinary radiologist or by someone with lots of experience who has received proper instruction on its use. At my practice, no one operates the ultrasound to diagnose a patient's condition until he or she has gone to educational seminars on its usage and has ultrasounded many normal patients first under the guidance of someone more experienced. The abnormal cannot be identified until one knows the appearance of the normal.

CT scans utilize radiograph technology and produce images of bones and organs more detailed than conventional x-rays. They can diagnose tumors or cysts that are missed by standard radiographs or that are not accessible to ultrasound imaging such as tumors or cysts located within boney structures such as the skull or vertebrae. This is also an excellent technology to find ruptured intervertebral discs and other diseases that can cause spinal cord compression. MRI utilizes nuclear magnetic resonance technology to produce even more precise images of the inside of the body. These technologies can sometimes find things missed by ultrasound, radiographs, bloodwork, or physical exam. But CT and MRI imaging can be relatively expensive and do not always reveal problems that cannot already be found by more economical means. For instance, a cyst on a kidney can certainly be seen by CT or MRI but it can also be identified by ultrasound which is less costly. A bone tumor can be identified with the more expensive technologies but can also often be identified by relatively less expensive radiographs or x-rays. The key in not falling into the trap of diagnostic overkill is to simply have tests done as indicated. If bloodwork and radiographs are sufficient to make the diagnosis, then go no further. If an ultrasound and biopsy reveals the answer, then stop right there. But if all other tests are unable to produce an answer, then consider the more sophisticated technologies such as MRI or CT.

These tests are often most productive if the patient is being checked for something specific. For instance, if a dog is having seizures, an MRI or CT could be used to view the brain to help find the cause of the seizures. Bloodwork, physical exam and possibly other tests would first be done to make sure the problem was not coming from areas outside the brain. It would often be a waste of time and money to do a whole body MRI and find that the brain was fine but the seizures were a result of a pancreatic tumor. Bloodwork and abdominal ultrasound would have found the problem and prevented quite a lot of expense in the process. If a cat is suspected of having lung cancer, then a CT of the chest may be considered. But first radiographs of the chest should be done. If no cancer is found, an ultrasound of the abdomen could be done. Some cancers spread from the abdomen to the lungs. If cancer in the abdomen is found by ultrasound, the CT may be not be necessary. However, if cancer in the abdomen is not found, then a CT of the chest only may be done. At this point, a CT of the whole body would simply be diagnostic overkill and the extra expense can be avoided.

The moral here is not to avoid newer technologies, but be selective on when and where these technologies are utilized. In the case of ultrasound, make sure the ultrasonographer is well qualified.