Words by: Lisa Whitfield
Most farmers are accustomed to the sight of the vet putting on their ultrasound gear to do pregnancy diagnosis at this time of the year. Modern ultrasound units are lightweight, ergonomically designed machines that allow the user to move about freely and work quickly and comfortably for a few hours at a time.
Did you know that ultrasound can be used for more than just pregnancy diagnosis in cattle?
With the ability to see more than 20cm deep through the skin and into the cow, the latest ultrasound units can be used to examine the internal organs quite readily. From viewing the heart and lungs in the chest, to the liver, stomachs and intestines in the abdomen, there are many organs that can be assessed for problems.
In a sick cow, a thorough clinical exam is the fundamental process that vets perform to identify abnormalities. Once all of her problems have been identified, a diagnosis can be made, or often, a list of potential diagnoses is made. Ultrasound can provide additional information by giving the vet an extra visual assessment of internal structures, which can be useful in decision making around the case, including helping to make a definitive diagnosis, deciding whether surgery is warranted, and assisting with giving a prognosis.
For cattle with internal problems, ultrasound gives us a window into the cow to provide more information, without having to make an incision. A few years ago, I was asked to examine a cow that was off her feed and off milk during spring. After the clinical examination, everything pointed clearly towards a problem in her abdomen, but it was unclear whether she needed surgery or not. Ultrasound was used to examine her abdomen, which showed that there was a blockage or a twist, and it allowed us to see that surgery was necessary to save the cow. We went ahead with surgery and when we opened her up, we found a 20cm long piece of intestine that was completely blocked with gravel. The blockage was able to be cleared, and the cow recovered, got in-calf, and went on to have a productive season.
In another case, a dairy heifer presented to me with signs of pneumonia. The signs were bad, but not enough to say she was not saveable. We performed ultrasound on her chest to help decide whether to go ahead with treatment. The ultrasound showed she had a huge build-up of fluid around her lungs, and the prognosis was unfortunately grim. In this case euthanasia was best choice for her. The use of ultrasound saved the farm a lot of money on treatments that would not have saved the heifer and it allowed us to end her suffering much sooner.
So how does ultrasound work? The transducer contains crystals that emit ultrasound waves into the body. The waves are bounced back by whatever they hit, and depending on how solid the object is, either more or fewer waves are bounced back to the transducer. A computer organises the signal to create an image, with more dense objects appearing whiter, and less dense objects appearing blacker. For example, bones are very solid and reflect almost all of the ultrasound waves, while soft tissues such as muscle appear as a variety of greys, and fluids such as urine are black.
Ultrasound can provide useful information to assist a vet in making clinical decisions for cases. Performing an ultrasound exam can improve the outcome for a sick cow significantly, whether through improved treatment plans, or allowing the decision to be made to euthanise.
Talk to your vet about what they can offer in this area – not everyone will carry an ultrasound unit around in the truck with them, but most will have a portable unit available that can do the job.
- Lisa Whitfield is a Manawatu-based production animal veterinarian.