What is a Diagnostic Ultrasound for Dogs and Cats?

Many people are surprised when they hear that the next stage in the medical work up for their dog or cat's disease is ultrasound. Most people think of it solely as a means of confirming pregnancy and it is used for that a but it is also useful in many other situations. Diagnostic ultrasound involves a special machine that sends high-frequency sound waves into the tissue and then elistense for the echoes that bounce back. A computer in the machine determines the timing and strength of the returning echoes and from them, constructs a two-dimensional image of the tissue being studied. By updating the image several times a second the computer can provide a television-like moving picture of the area of interest.

Ultrasound has been used for two decades at larger veterinary colleges, but due to the expense of the equipment, it was not available to the average general practitioner. Today, most large cities will now have at least one veterinarian who has an interest in diagnostic ultrasound and the equipment to conduct the examination. Here are some of the reasons your veterinarian may recommend an ultrasound when determining a diagnosis in your cat or dog:

  • To examine internal organs: an ultrasound is an excellent, non-invasive tool that is very useful to study the heart and major blood vessels leaving it, as well as the liver, spleen, kidneys, pancreas, adrenal glands, urinary bladder, prostate gland, and other internal organs. It is a non-invasive option in cases where the next step would often be an exploratory surgery.
  • To check for cancer: cancers, abscesses and other abnormal tissues are also often easily seen with ultrasound. The exact nature of the problem, sometimes cannot be determined without an actual biopsy but in these cases, ultrasound can help guide the veterinarian to the exact location of the problem. Ultrasound may also be used to help guide a biopsy instrument to allow a portion of the tissue to be removed for diagnosis of disease without having to do an actual surgery. Many ultrasound-guided biopsies can be done with just a local anesthetic.
  • To confirm a pregnancy: pregnancy diagnosis is an important use of ultrasound. Early and accurate diagnosis can help guide breeding programs. The earliest that a pregnancy has been seen in dogs using an ultrasound is 12 days gestation, but the recommended time should be 25 to 30 days post breeding. One important point is that the ultrasound cannot be used to accurately count the number of pups a bitch is carrying. In some cases an exact count can be done, but often we are limited to saying whether she will have a large litter or there are only two or three pups.

Is an Ultrasound Safe?

Ultrasound is an extremely safe procedure. No short or long-term problems associated with the proper use of diagnostic ultrasound have been seen. The only telltale sign is that the hair in the area to be studied must be clipped to do a good ultrasound exam.

Like any other medical procedure, ultrasound is not magical. The image and the information gained is only as good as the machine being used and its operator. Experience and study are needed to interpret the ultrasound images just as they are for reading x-rays or interpreting laboratory results. Often, ultrasound will not achieve the final diagnosis, but instead must be looked at as a piece a often a large piece a of the entire puzzle. Your veterinarian has to obtain enough pieces of the puzzle so the final picture can be seen.

Ultrasound is a part of this evolution in veterinary medicine, and it is likely to become more readily available in the future.

Article submitted by: © Daniel Joffe, DVM

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