Definition of ultrasound vs radiography

Ultrasound is a non-invasive imaging technique. It is also called sonography or ultrasonography. It uses high-frequency sound waves, higher than the audible frequency, to produce the images. These waves are sent out and bounced back or respond with an echo (hence their name). This is why this technique is used in the evaluation of soft tissues. Provides a two-dimensional moving image. The most used is abdominal ultrasound. This is used to evaluate multiple organs, both the digestive and reproductive and excretory systems: stomach, intestines, bladder, kidneys, prostate, spleen, liver, uterus, womb…

Radiography is a radiological diagnostic technique that obtains a static two-dimensional image using X-ray or gamma-ray radiation of radioactive isotopes. The beams of X-rays pass through the body absorbing in different amounts depending on the density of the structure through which they pass. It is quick and painless and provides images of the body’s internal systems. It is also considered a non-invasive technique, but as we have mentioned, the patient must be exposed to a small radiation dose.

When to use ultrasound vs radiography

• Radiography is an excellent diagnostic test for joint or trauma problems: fractures, dislocations… However, ultrasound is the appropriate test for evaluating soft tissues, organs or viscera.
• Ultrasound is also the best technique to assess the size or presence of more or less small masses.
• For the diagnosis of pregnancy, see the days of gestation. However, it is best detected with an x-ray at term to know the exact number of puppies.
• As for foreign bodies, radiography cannot detect the tissue, for example, unless there is already an obstruction. However, with the ultrasound, you can see if a sock is rolling around in the stomach. 
• The radiograph is indicative. As the first step in an evaluation, when performing the x-ray, you will be able to observe that the heart is more extensive than it should be. Therefore, you will have to complete an ultrasound if you want to make a more specific evaluation since, with this technique, you will be able to evaluate the function of the heart valves, the entrance of the arteries or the exits of the veins of the heart.
• An ultrasound can also see if there is pulmonary hypertension. Pulmonary hypertension cannot be detected with radiography.

Advantages of using ultrasound vs radiography

• There has been an increase in the use of the ultrasound technique instead of the radiological procedure for some time now in veterinary medicine. This has an explanation. Both radiography and ultrasound are good techniques, each on its own. But ultrasound has advantages over radiography because it encompasses a greater breadth of study, among other things. We leave you here some benefits of using ultrasound compared to radiography:
• Radiography emits ionising radiation that, although it is a small amount, is radiation. This radiation can be harmful to the patient and the professional. Ultrasound emits harmless waves. This means that protection measures, permits, insurance or specific measures are not required for its performance, as is the case with radiography.
• The image of both techniques is two-dimensional, but ultrasound is dynamic, allowing us to see movement, as in the case of fetuses in the womb. However, the X-ray image is fixed, which can be helpful in some instances. In addition, the radiographic picture is more explicit. No matter how clear it is, being static in many cases, it is insufficient, requiring an ultrasound to see specific movements.
• Ultrasound allows us to see the organs and differentiate between tissue densities, while radiography does not. Of course, the X-ray image will be more precise when evaluating bone matter or high-density objects.
• In case of intestinal obstruction, radiography cannot detect certain elements such as plastics, wood, fabrics or clothing, while ultrasound does have the ability to distinguish them.
• In a picture of urinary disorders, radiography would allow us to detect the presence of radiopaque stones. But if we want greater precision, we must use the ultrasound technique. An ultrasound would confirm or rule out renal obstruction. It would also inform us whether the block is caused by stones, tumours or clots.
• Ultrasound also has the advantage that it can be combined with other simultaneous techniques. Examples would be ultrasound-guided punctures or contrast to detect the animal’s lesions better.
• Knowing how to perform them is as important as knowing how to interpret them. The interpretation of ultrasound requires more technical knowledge than that of radiography. The radiograph is usually solved by veterinarians since no specialisation is required. However, to perform an ultrasound and especially to interpret it, the ideal is for it to be done by a specialist.
• A very positive aspect of radiography is that it is cheaper. It is within reach of any veterinarian; almost any centre has a ray machine. In the case of ultrasound, the cost of hiring a specialised professional must be added.

Abdominal ultrasound

Of the ultrasounds, the most performed is the abdominal one because it covers a multitude of organs and viscera that require evaluation for different ailments.

Abdominal ultrasound is indicated in the following cases:

• I suspect a foreign body, either in the stomach or intestine. As we explained previously, if it is not visualised in radiography, an ultrasound should be performed since the radiography does not differentiate specific tissues.
• In the case of cryptorchidism. Cryptorchidism is a developmental disorder in which there is an incomplete descent of one or both testicles, remaining internally. In the case of cryptorchidism, surgery must be performed to extract the testicle from the outside. If it remains internal, it can become a tumour or necrotic and cause infection. Abdominal ultrasound is used to assess the status of the testis.
• In case of discomfort or alterations in the animal’s urine, an abdominal ultrasound should be performed to confirm or rule out kidney stones. In this, crystals at the renal level can be evaluated. If this is not the cause of the obstruction, it would inform us of the other possible reason.
• Abdominal discomfort can encompass a multitude of possible alterations. Animals cannot tell us what is happening to them; although we will know which area bothers them the most by palpation, we will need an imaging technique to confirm or rule out the diagnosis. In this case, we can make a first simple abdominal X-ray; it will often fall short. To evaluate abdominal organs or viscera, abdominal ultrasound should be used.
• For pregnancy diagnosis. Either to confirm pregnancy, for the feasibility of pregnancy since the ultrasound, by distinguishing the movement, will detect the heartbeat; or to detect possible malformations. To determine the number of puppies, it could be done by ultrasound; in this case, it will be more precise to perform an X-ray at term.

Ultrasound performed at Vellcan Veterinaries.

• For cyst punctures: in case a sterile urine collection has to be performed through a hole in the bladder. By having the ultrasound image of the bladder, we can perform a safe cyst puncture.
• I was suspecting ascites: free fluid in the abdomen. Ascites can be due to different causes: liver problems, trauma to internal organs, inflammation of the peritoneum, tumours, coagulation disorders, etc. It is manifested by abdominal distension that usually occurs together with the animal’s discomfort. Knowing the cause of free fluid in the abdomen is essential for proper diagnosis and treatment. Ultrasound or radiography can be used to confirm the presence of free liquid from the waist. However, extraction will require the use of abdominal ultrasound.
• How often do we find a mass inside the abdomen or internal organs in the consultation? Gatherings can be detected with radiography and ultrasound, but when extracting a sample, the same will happen as in the previous point; an abdominal ultrasound will be used as a guide.