This X-ray shows a spinal fracture a dog suffered in a car accident. Veterinary Specialty Care/provided
The hardest part of my (Perry Jameson) job as a veterinary internist is figuring out what the underlying problem with a patient is.
My patients come in with a certain set of symptoms. It can be anything from fever, vomiting, diarrhea, lameness, painful abdomen to the least specific of all: anorexia. Before I can begin therapy, I have to determine what the underlying issue is that is causing these presenting symptoms.
The dog or cat cannot tell me how they feel, what they may have eaten or where it hurts. I depend on Mom and Dad to try to provide some of this information to the best of their ability. Sometimes this can be diagnostic, such as if they saw their cat eat a string. But more often, it is not.
Laboratory testing may reveal the cause if the patient has renal disease, liver failure or electrolytes that are abnormal. If these tests are normal, then the next step is to begin imaging.
The different imaging procedures used in veterinary medicine are X-rays, ultrasound, CT scan and MRI. These techniques all provide ways to look inside of the animal without actually going to surgery.
When explaining what I hope to accomplish with an imaging technique, I also have to explain the limitations. In some ways, taking an image is similar to the kindergarten post office game. In this game the children are seated in a circle. The first child whispers a message into the child seated next to her. This message is whispered from child to child around the circle. Inevitably, by the time the final child states the message, it has changed.
This fact has to be taken into account when we perform imaging. The pictures are never as good as the real thing because they are altered in some way. Getting a look inside requires surgery, but images are much safer to obtain, so we start with these.
X-rays usually do not require any sedation, are the least expensive and with digital X-rays, they can be obtained in seconds. They are great for assessing changes to bones such as tumors or fractures. Air-filled structures such as the lungs and loops of intestine can be evaluated as well.
When looking at an X-ray, I have to remember that I am assessing a three-dimensional structure in one dimension. For this reason we often take two to three images of the same area from different angles. Free fluid in the abdomen or chest cavity will “white out” the image making assessment difficult.
One of the biggest drawbacks with X-rays is the nurses taking the images are being exposed to radiation. Protective gowns and gloves are worn, and we wear badges to tell us when we have been exposed to too much radiation and need a break.
Ultrasound usually does not require sedation. It requires the person performing the ultrasound to have advanced training to obtain the proper images as well as interpret them.
Ultrasound is especially useful at looking at abdominal structures and the heart. It allows us to look inside the organs for changes. It is quick and does not expose us to any dangerous radiation. Fluid can easily be detected and actually aids in performing the imaging. It is not great for looking at air-filled areas such as the lung or dense structures such as bone.
CT scans provide greater detail than X-rays and ultrasound and may pick up abnormalities missed on those two. Most CT scanners used today are quick, getting images in minutes. Computers can reconstruct the CT images into three-dimensional pictures helping us make the diagnosis.
CT scans are a great way to look at bones, the nasal passage and sinus cavities, blood vessel abnormalities or clots and urinary anomalies. They are a great way to look for small tumors in the chest or abdomen that could be missed with X-rays and ultrasound.
The biggest drawbacks are it requires general anesthesia to keep the dog or cat still while moving through the tube, and it is more expensive than X-rays and ultrasound.
MRI is the newest imaging technique we use on a daily basis. It is the most expensive machine to operate, requires general anesthesia and takes longer than a CT scan. Those negatives aside, it provides incredible images, especially of the brain and spinal cord.
The ability to image our patients in such detail aids in getting an accurate diagnosis and making the appropriate recommendations.
Dr. Henri Bianucci and Dr. Perry Jameson are with Veterinary Specialty Care LLC. Send questions to firstname.lastname@example.org.