November 27, 2025
Why giant breeds test ultrasound’s limits
Ultrasound is an extraordinarily useful tool for general practice vets, but once a dog reaches that 40 to 50 kilogram range, the physics stop being polite. Tissue penetration quickly becomes the bottleneck. In some giant-breed dogs, the liver sits so deep that ultrasound starts to lose definition well before you get the detail you need. And that’s really the heart of the conversation with giant breed patients: ultrasound still absolutely earns its place, but only when what you need to see is close enough to the transducer for sound to carry meaningful detail.
In many large dogs, deep organs such as the liver and pancreas can sit so far from the body wall that resolution becomes compromised. The spleen, however, remains reliably cooperative due to its superficial position, and the bladder, kidneys, and reproductive tract often remain accessible. This is where practical judgement matters. If your clinical question lies deep in the abdomen, CT may provide a more accurate answer. If it lives close to the surface, high-quality ultrasound can still be the fastest and gentlest first step, and often the most cost-effective one for SA clients.
A Practical Comparison for SA Vets
|
Clinical Question |
Ultrasound |
CT |
| How well does it penetrate deep structures? | Limited by depth in large and giant dogs. Physics restricts how far sound waves can travel before image quality drops. | Excellent depth access. CT visualises deep abdominal and thoracic structures without the same physical limitations. |
| Best-use scenarios | Soft tissue detail, focal organ assessment, real-time imaging, fluid detection and guided sampling. | Complex abdominal disease, thoracic investigations, masses that sit deep or behind gas, vascular assessment and pre-surgical planning. |
| Where ultrasound struggles in big dogs | Deep liver, pancreas, adrenal glands and retroperitoneal structures may be difficult to access or interpret reliably. Gas and body size can obscure windows. | CT bypasses gas shadows and depth constraints, allowing clearer assessment when ultrasound windows are limited. |
| Patient stability | Useful when the patient cannot be transported and needs an in-clinic assessment. Quick, bedside, low stress. | Requires transport and sedation. Not ideal for unstable patients unless at an emergency facility. |
| Accuracy in detecting subtle pathology | Very operator dependent. May miss deep or small lesions in giant breeds due to limited acoustic access. | High sensitivity for deep lesions and structural abnormalities, with consistent image quality regardless of patient size. |
| Turnaround and accessibility | Immediate findings provided in the clinic, maintaining continuity of care. | Dependent on availability of referral centres and patient stability. Results are often delayed compared to bedside ultrasound. |
| When SA vets typically choose it | When clinical questions are accessible to ultrasound and the patient benefits from in-clinic imaging. | When the anatomy in question sits beyond ultrasound’s reach or when a comprehensive cross-sectional study is needed. |
Ultrasound’s sweet spot in giant patients
Ultrasound plays a strong, often underestimated role in giant breeds when the question is targeted and anatomically reachable. A classic example is the Wolfhound with a suspected splenic mass. Because the spleen sits close to the abdominal wall, ultrasound can offer excellent detail and immediate clinical value without the need for anaesthesia or the cost of advanced imaging. It also allows for on-the-spot assessment of free abdominal fluid, bladder changes, cystic structures, or any other abnormalities affecting the superficial urogenital tract.
What tends to matter most is not the dog’s size, but the depth of the organ and the nature of the question. If you’re staging liver disease, mapping vascular anomalies, or clarifying an equivocal hepatic lesion, CT brings you the spatial mapping that ultrasound simply cannot. For everything else that sits near the surface, ultrasound continues to be a gentle, real-time diagnostic sounding board, especially for Adelaide and regional SA clinics aiming to reduce unnecessary referral steps.
How SA Veterinary Sonography supports these cases
For SA clinics grappling with complex abdominal questions, our role is to support the judgment you are already using. We provide in-clinic ultrasound that helps you answer superficial or readily accessible questions quickly, keeping the patient comfortable and avoiding unnecessary referral steps. And when the clinical question clearly sits beyond ultrasound’s reach, we can help confirm that early so you can guide owners toward CT with confidence. It keeps the workflow practical, reduces uncertainty and lets you stay at the centre of the case while still having a diagnostic sounding board when the anatomy gets deep.
If you’d like to arrange an ultrasound or talk through a case, we’re always happy to help.
About the Author
Dr Jennifer Judd BVMS GCertSAUA MANZCVS (Radiology) is a visual thinker and ultrasound devotee with a knack for turning complex scans into practical answers. After a decade in general practice, she founded SA Veterinary Sonography to bring precision imaging into the hands of everyday vets.
Dr Jen is known for her calm presence, sharp eye, and collaborative style – helping clinics navigate tricky cases without sending patients offsite. When in doubt, she’s your diagnostic sounding board.
Mobile Veterinary Ultrasound Services
Advanced in-clinic ultrasound for accurate diagnosis and treatment planning, delivered through abdominal, thoracic, cardiac and reproductive imaging.
Abdominal
Comprehensive abdominal imaging assessing organs, effusion, masses, inflammation, and gastrointestinal changes.
Thoracic
Targeted thoracic ultrasound evaluating pleural effusion, lung changes, and masses, ideal for unstable or dyspneic patients.
Echocardiogram
Detailed cardiac imaging assessing structure, chamber size, function, and mitral valve disease staging for informed treatment.
Reproductive
Focused urogenital imaging assessing pregnancy, pyometra, prostatic changes, urinary tract issues, and suspected bladder stones.
Abdominal
Comprehensive abdominal imaging assessing organs, effusion, masses, inflammation, and gastrointestinal changes.
Thoracic
Targeted thoracic ultrasound evaluating pleural effusion, lung changes, and masses, ideal for unstable or dyspneic patients.
Echocardiogram
Detailed cardiac imaging assessing structure, chamber size, function, and mitral valve disease staging for informed treatment.
Reproductive
Focused urogenital imaging assessing pregnancy, pyometra, prostatic changes, urinary tract issues, and suspected bladder stones.
Frequently Asked Questions
Have questions? We’re here to support you. Below are answers to common queries about our veterinary ultrasound services.
Can ultrasound reliably assess the liver in a 50kg dog?
Often, the detail is limited because of depth. In many giant breeds, the liver sits too far from the abdominal wall for optimal resolution. Ultrasound may still detect major pathology or free fluid, but CT usually provides clearer assessment for deeper hepatic questions.
What imaging should I start with for a suspected splenic mass in a giant dog?
Ultrasound is usually appropriate because the spleen is a superficial organ and remains well-visualised even in very large patients. It offers fast confirmation and helps guide further decision-making if CT is needed.
When is CT more cost-effective for SA clients?
CT can be more efficient when the diagnostic question involves deep abdominal organs or when surgical planning is likely. It may reduce the need for repeated imaging and provide comprehensive mapping in a single session.
Can both CT and ultrasound be used together?
Yes. Many cases benefit from pairing modalities, such as when ultrasound identifies a hepatic lesion that requires CT to determine margins, blood supply or surgical approach.
Do large dogs always need sedation for imaging?
Ultrasound rarely requires sedation unless the patient is painful or anxious. CT generally requires either heavy sedation or general anaesthesia to ensure complete stillness for accurate image acquisition.
How do I decide which modality fits my case in Adelaide or regional SA?
Start with your clinical question. If it is superficial, an ultrasound may be sufficient. If it involves deeper structures, CT may provide a better answer. If there’s any uncertainty, we’re happy to talk it through and help guide the best approach.