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By March 20, 2022March 7th, 2023No Comments

The ultrasound is a very important diagnostic tool in the veterinarian’s arsenal. Today I am going to talk about what the ultrasound is, how it is used and what it can be used for to help your animals. The ultrasound allows us to visualize structures below the surface of your animal’s skin without having to do invasive procedures such as surgery.

The ultrasound machine uses high frequency sounds waves to visualize structures inside of an animal. The probe of the machine emits the sound waves, which pass through tissues beneath the skin. As the waves hit different structures, some of the waves bounce off and are reflected back to the probe. The machine is able to calculate distances at which the waves were reflected and creates a black, white and gray image of the structures encountered.


Diagram of ultrasound waves emitting from ultrasound probe. Image from:

Ultrasound is commonly used for many species of animals. For dogs and cats, abdominal ultrasound is commonly used to diagnose diseases such as pymetra or tumors. It is also used to direct the biopsy of various organs such as the liver.

Picture of abdominal ultrasound of a dog with a pyometra (uterine infection). Courtesy:

In large animals, ultrasound is primarily used to diagnose reproductive conditions. In cattle, ultrasound is routinely used to diagnose pregnant animals as early as 32 days of pregnancy. If the cow is not pregnant, the ultrasound is than used to scan each ovary to determine possible reasons for why she did not get pregnant. It is a powerful tool, because cows that are not pregnant, cost money (ie; cows must produce offspring to earn their keep). For cows, the ultrasound is performed rectally, which allows us to image the reproductive tract early in pregnancy.

Diagram of rectal ultrasound in the bovine. Courtesy:


Photo of bovine fetus at 35 days. Courtesy:

In sheep and goats, using ultrasound to view the reproductive tract is a little different. You can get probes and special introducers to place the probe in the rectum (human arms are a bit big to rectal these animals). Another method is to scan across the abdominal wall from underneath the animal. This method is least invasive and can allow the veterinarian to count fetuses within the uterus.

Photo of ultrasounding the abdomen of a ewe. Courtesy:

Picture of a sheep ultrasound with twins. Courtesy:

Ultrasound of animals to determine pregnancy status has many advantages. Learning whether or not animals are pregnant early is critical to feeding those animals appropriately to support pregnancy. Animals that fail to conceive can be culled or repurposed. Identifying if sheep or goats have twins vs a single fetus is crucial as those ewes or does carrying more than 1 fetus will require more energy in their diet than those carrying singles.

There are, of course, many more uses for the ultrasound in veterinary medicine. Tendon injuries, pneumonia in calves, liver biopsies in cattle, to name just a few. Stay tuned for more blog posts about diagnostics that can benefit your herd or flock.

References (and to learn more):