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Reason for Fasting a Dog Before the Ultrasound

Dehydration in Dogs

Dog owners are accustomed to fasting their dogs before surgery, but may be wondering what's the purpose of fasting a dog before an ultrasound. Also known as ultrasonography, an ultrasound is an imaging technique that allows your vet to visualize internal body structures courtesy of a beam of sound waves emitted by a probe in contact with your dog's skin. Sounds waves may pass through tissues, or they may be reflected or absorbed. The sound waves that are reflected, return to the probe as echoes which are then converted into images that are displayed live on a monitor.

Safe and effective, an ultrasound is an invaluable non-invasive imaging technique that comes useful in veterinary medicine for evaluation and diagnostic purposes. Veterinarian Dr. Joanne Fernandez-Lopez explains why fasting your dog for an ultrasound can be important.


So Why does My Vet Want My Dog Off Food Before the Ultrasound?

The food may cause what is called an acoustic shadow in the image. Acoustic shadowing is defined as a signal void behind structures that strongly absorb or reflect ultrasonic waves.

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This means that the food would be absorbing all the signal sent by the ultrasound probe that the veterinarian is placing on your pet’s skin.

This shadow behind the food then may hide other organs in the image which will not allow the clinician to perform a full and accurate study.

The problem with this is that we may be running the risk of missing important information that can help the clinician reach a diagnosis. In some instances, the clinician may need to repeat the study or reschedule for another day.

About the author 

Dr. Joanne Fernandez-Lopez is an emergency veterinarian on staff in the Emergency and Critical Care Department at Florida veterinary Referral Center (FVRC).

joanne fernandez

Originally from Puerto Rico, Dr. Joanne Fernandez-Lopez graduated from North Carolina State University – College of Veterinary Medicine in Raleigh, NC. Prior to joining FVRC, Dr. Fernandez-Lopez worked in small animal general practice and as a relief doctor in South East Florida. Her professional interests include dermatology, surgery, internal medicine, preventive medicine, reptile medicine and practice management.

In her free time, Dr. Fernandez-Lopez enjoys relaxing at the beach, paddle boarding, kayaking, and surfing. She has a small Tibetan spaniel mix named Carlitos.

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