Introduction
Dog ultrasounds are a common diagnostic tool used by veterinarians to evaluate a dog’s health and examine things like pregnancy, internal organs, and potential medical issues. Ultrasounds use high-frequency sound waves to create images of the inside of a dog’s body in real-time. This allows vets to gain valuable information without invasive procedures.
One question dog owners often have is just how accurate ultrasounds really are. Like any diagnostic test, ultrasound results aren’t 100% foolproof and have some margin of error. There are instances where ultrasound results can be inconclusive or even misleading in rare cases. Understanding the accuracy of dog ultrasounds and why errors occasionally occur can help owners better interpret results.
How Ultrasounds Work
Ultrasound technology uses high-frequency sound waves to produce images of structures inside the body (Source: https://vcahospitals.com/know-your-pet/ultrasound-examination-in-dogs). A device called a transducer emits sound waves at frequencies above the range of human hearing and directs them at the area being examined. When the sound waves encounter different tissues and fluids, some of the waves are reflected back to the transducer. These reflected waves are converted into electrical impulses that a computer then translates into images on a screen.
The sound waves themselves are harmless and painless. Ultrasound allows your veterinarian to see internal organs and structures in motion in real-time. It is useful for evaluating the architecture, size, and shape of organs, as well as detecting abnormal masses or fluid accumulations. The quality of ultrasound images depends on the experience and skill of the ultrasonographer as well as the cooperation of the patient (Source: https://www.petmd.com/dog/general-health/ultrasounds-dogs-and-cats-everything-you-need-know).
Uses of Dog Ultrasounds
There are several common uses for ultrasounds in dogs:
Checking pregnancy and monitoring fetuses – One of the most common reasons for dog ultrasounds is to confirm pregnancy, determine how many puppies are expected, and monitor fetal development. Ultrasounds can detect heartbeats in fetuses as early as 3-4 weeks into pregnancy (source).
Evaluating organs – Abdominal ultrasounds allow for the visualization of the internal organs, such as the liver, kidneys, spleen, lymph nodes, urinary bladder, etc. This can help detect masses, cysts or abnormalities (source).
Assessing the heart – Cardiac ultrasounds are used to examine the heart walls, valves and blood flow to screen for defects or disease. This can diagnose conditions like cardiomyopathy or valvular disorders (source).
Checking for internal injury or bleeding – Ultrasounds can find fluid accumulation, bleeding, or damage to organs after trauma or an accident.
Guiding medical procedures – Ultrasound allows real-time visualization to safely guide needle biopsies, drain fluid from cysts, or place catheters.
Screening for cancer – Ultrasound can detect masses or abnormalities that may indicate cancerous tumors in organs like the spleen, liver, kidneys, etc.
Accuracy of Ultrasound Results
Overall, ultrasound is an extremely accurate way to diagnose various conditions in dogs when performed by a skilled veterinarian. According to one study, ultrasound was able to correctly identify the location of masses in the adrenal glands with 98% specificity for the left adrenal gland, 87% for the central part, and 89% for the right adrenal gland (https://pubmed.ncbi.nlm.nih.gov/26749405/).
For diagnosing pregnancy in dogs, another study found that real-time ultrasound resulted in 99.3% overall accuracy. The sensitivity was 98.7% and the specificity was 100% (https://link.springer.com/content/pdf/10.1186/BF03547247.pdf).
However, there are certain factors that can affect the accuracy of ultrasound results. Things like the skill of the sonographer performing the scan, the quality of the ultrasound machine, the cooperation of the dog during the procedure, and the timing of the scan relative to the dog’s pregnancy term can all impact the clarity and interpretation of the images.
Reasons for Inaccurate Results
There are several reasons why a dog ultrasound may produce inaccurate results, leading to incorrect predictions about the number of puppies or other details. Some of the main reasons include:
Poor imaging quality – The ultrasound image relies on the skill of the technician in capturing the right angles and views. If the image quality is blurry or obstructed by gas or feces, it can be difficult to get an accurate count of puppies.
Inexperienced technician – Counting puppies via ultrasound requires practice and expertise. Less experienced technicians may miss seeing all the puppies, especially if they are stacked on top of each other or hidden behind tissues.
Fetal position – Curled up puppies can obscure each other on the scan. Puppies positioned away from the probe can also be missed.
Timing – Too early in pregnancy, there may not be enough definition to see puppies. Too late, and crowding obscures the view.
Maternal interference – The dog’s abdominal wall tissue, fat, fluids and gas can interfere with getting a clear scan.
Equipment factors – Lower quality ultrasound machines may produce less accurate images.
Case Studies
There are some documented cases where a dog’s ultrasound produced inaccurate or incomplete results that led to an incorrect diagnosis. For example, one case study published in the Journal of Veterinary Internal Medicine described a pregnant dog that underwent two separate ultrasounds. The first ultrasound detected only two puppies, while the second ultrasound found a total of seven puppies in the litter (Gelberg et al., 1999 https://link.springer.com/content/pdf/10.1186/BF03547247.pdf). This large discrepancy suggests the first ultrasound missed several puppies.
Another case outlined in Clinician’s Brief described an 8-year-old dog that received an abdominal ultrasound after vomiting and diarrhea. The radiologist did not detect any abnormalities besides mild intestinal wall thickening. However, an exploratory laparotomy later revealed a foreign body obstruction in the jejunum that required surgery (McConnell, 2015 https://www.dvm360.com/view/ultrasound-case-studies-proceedings). This example demonstrates how some issues can be missed on ultrasound if the obstruction is not in the exact scanning plane.
While useful diagnostic tools, these case studies confirm ultrasounds can sometimes fail to identify problems or underestimate their severity. Getting follow-up imaging or tests is crucial for an accurate diagnosis in challenging cases.
Improving Accuracy
There are several things you can do to help ensure your dog’s ultrasound results are as accurate as possible:
Use an experienced ultrasonographer. Look for a vet or clinic that specializes in imaging and has significant experience performing dog ultrasounds. Their skills and expertise can make a big difference in capturing clear images and making accurate interpretations.
Have the ultrasound done when your dog is properly prepared. For example, when checking for pregnancy, the ideal timing is between day 20-35 of gestation. Following any preparation guidelines from your vet, such as withholding food and water beforehand, can allow for better visualization.
Get multiple views and measurements. The ultrasonographer should capture images from multiple angles and take measurements of any abnormalities 3 times from different perspectives. The more complete the exam, the less room there is for error.
Use the best equipment available. While some vets may offer ultrasounds with basic machinery, visiting a specialty clinic with cutting-edge diagnostic imaging capabilities can provide greater clarity and detail for identifying even tiny structures.
Review the results thoroughly with your veterinarian. Go through the images together and make sure to clarify any unclear findings, get second opinions if needed, and understand if any follow-up testing should be done to confirm initial results.
Being an engaged pet owner, asking questions, and partnering closely with your veterinary team can go a long way towards getting the most accurate ultrasound results possible. Though imaging technology has limitations, the expertise and care of the staff performing the ultrasound is often the biggest factor in reducing errors.
Confirming Results
While ultrasound scans provide valuable information, the results should be confirmed with other diagnostic tests before making any major medical decisions, according to Carolina Veterinary Specialists. This is because even quality ultrasound equipment can miss signs of disease in some cases.
Some ways vets may confirm ultrasound findings include:
- Blood tests – To check for abnormal cell counts, organ function, or disease markers
- Biopsies – Taking tissue samples to analyze cells under a microscope
- X-rays – Providing images of bone and dense tissue
- MRI or CT scans – Creating more detailed 3D images of organs and tissues
While an ultrasound can suggest potential problems, other tests often provide definitive diagnosis. Discuss options with your vet if the ultrasound results are ambiguous or concerning. Multiple perspectives lead to the most accurate understanding of your dog’s health.
Talking to Your Vet
When reviewing your dog’s ultrasound results with your vet, there are some key questions you may want to ask:
According to Ultrasound for Dogs and Cats: What Pet Owners Want to Know, some good questions include:
- What exactly do the ultrasound results show?
- Is anything abnormal or concerning in the images?
- Do the results indicate any specific conditions or issues?
- Do you need to do any additional tests based on these findings?
- What would the next steps be if the results are abnormal?
- How confident are you in the accuracy of these results?
- Is there anything I should monitor with my dog after the ultrasound?
- How should I understand or interpret these results?
Having an open conversation with your vet can help you better understand the ultrasound findings and what they mean for your dog’s health and treatment.
Conclusion
To summarize, dog ultrasounds are a useful diagnostic tool that allow vets to see inside a dog’s body in real time. However, they are not 100% accurate. Results can sometimes be inconclusive or open to interpretation. There are many factors that can contribute to inaccurate readings, from the skill of the technician to the cooperation of the dog.
While ultrasound is generally very reliable, it’s important to understand it’s not a perfect science. Vets rely on a combination of test results, medical history, and clinical signs to make an accurate diagnosis. If an ultrasound result doesn’t seem to align with other findings, additional testing may be needed to get to the bottom of things.
By being an informed pet owner and communicating openly with your vet, you can get the most out of this helpful imaging technique. While an ultrasound may not provide all the answers, it gives vets a window into your dog’s health and lets them provide the very best care.