Adrenal Gland Ultrasound in Dogs (and Cats): The Technique That Changes Everything
- Echo Vet Solutions
- Jul 15
- 10 min read
Introduction: The Organs Everyone Skips
Ask any vet how they feel about scanning adrenal glands and you'll usually get the same response, a knowing smile, a slight wince, or a quiet confession that they simply "skip them." And honestly? That's understandable. These are tiny, deeply situated structures, tucked away in a region of the abdomen where fat, ribs, and major vessels all compete for your attention. Even experienced sonographers describe them as among the most technically demanding structures to consistently image.
But here's the thing: the adrenal glands matter clinically. A lot. And with the right technique, the right landmarks, the right probe pressure, the right systematic approach, they are far more accessible than most vets believe. You don't need to be a radiologist to find them. You just need a method.
This post walks you through exactly that. We'll cover why visualising the adrenals is worth the effort, how to actually find them reliably in dogs (with a note on cats), what normal looks like, and what changes should make you sit up and take notice.
Why the Adrenal Glands Deserve a Spot in Your Abdominal Scan
The adrenal glands sit at the intersection of several common presentations in general practice. Hyperadrenocorticism (Cushing's syndrome) is one of the most frequently diagnosed endocrinopathies in small animal medicine, affecting predominantly middle-aged to older dogs. Your Cushing's patients, the PU/PD dogs, the pot-bellied, polyphagic, panting ones, are exactly the patients where adrenal assessment on ultrasound changes your clinical picture.
Beyond Cushing's, the adrenal glands are relevant whenever you are investigating hypertension, an incidental abdominal mass, unexplained weakness in a cat, or a clinical picture that just doesn't quite fit elsewhere. Differentiating pituitary-dependent from adrenal-dependent hyperadrenocorticism, identifying a unilateral adrenal tumour, assessing for vascular invasion, these are questions that ultrasound is uniquely placed to help answer, right there in your practice, in real time.
The adrenal glands are also worth scanning as part of a complete abdominal study even when you're not specifically chasing endocrine disease. Finding an unexpected adrenal mass or assessing bilaterally small glands in a collapsed Addisonian patient can be genuinely practice-changing. The point is this: once you have a reliable technique, the adrenals stop being something you avoid and start being something you check.
Anatomy First: Know Where You're Going
The single most important step in finding the adrenal glands is understanding their anatomical relationships with the major abdominal vessels. The kidneys are a useful starting point, but they are not the primary landmark — and relying on the kidneys alone will regularly lead you astray.
In dogs, the two glands differ in both shape and position:
The left adrenal gland is the more forgiving of the two. It sits craniomedial to the left kidney, lying ventrolateral to the aorta, positioned between the origin of the cranial mesenteric artery and the left renal artery. In the longitudinal (sagittal) plane, it has a classic "peanut" or "dumbbell" shape — centrally constricted with two distinct poles. In larger or leaner dogs it may appear more elongated and slender. It is hypoechoic relative to the surrounding retroperitoneal fat and can be identified as a discrete structure once you've established your aortic landmark.
The right adrenal gland is consistently more difficult to image. It lies craniomedial to the right kidney, dorsal or dorsolateral to the caudal vena cava (CVC), and sits cranial to both the right renal artery and the cranial mesenteric artery. Its shape has been described variously as "comma-shaped" or "arrowhead" — less symmetrical than the left. Its proximity to the CVC is actually your key tool for finding it: the right adrenal gland is firmly associated with the lateral aspect of the caudal vena cava, and the vessel is your guide.
The phrenicoabdominal vein is also worth knowing about. It runs along the ventral surface of each gland and, when visible on colour Doppler, serves as a useful anatomical marker — particularly for confirming gland identity and, in pathological cases, assessing for vascular involvement.
In cats, the anatomy is broadly similar but with a few practical differences. Both glands tend to sit slightly more cranially along the main abdominal vessels, just cranial to the cranial pole of each respective kidney. Feline adrenal glands do not show the distinct peanut waist characteristic of dogs — instead they are consistently described as oval, bean-shaped, or bilobed, and are also hypoechoic with a thin hyperechoic halo in many cases.
Equipment and Patient Preparation
You do not need a specialist machine to scan the adrenal glands — but you do need adequate frequency and image quality. A high-frequency transducer (7.5 MHz or above, ideally a microconvex or linear probe depending on patient size) gives the resolution necessary to distinguish a small hypoechoic structure from surrounding fat. Deeper patients — large, overweight, or deep-chested dogs — will challenge you, and in these cases reducing your frequency slightly to penetrate deeper may be a necessary compromise.
Standard abdominal preparation applies: clipping the hair over the relevant area and using adequate coupling gel. A dorsal recumbency position is commonly used and works well for both adrenals, though some operators prefer right lateral recumbency for the left adrenal, and left lateral for the right. Either approach can work — consistency matters more than the specific choice. In cats, most tolerate scanning without sedation in a quiet, dimmed room.
Colour Doppler is a genuinely useful adjunct here, and if your machine supports it, use it. It makes identifying the aorta, CVC, and branching vessels significantly quicker, especially when fat or bowel gas is obscuring your landmarks.
Step-by-Step: Finding the Left Adrenal Gland in Dogs
This is the one to start with — it is reliably easier, less obscured by ribs, and a good way to build your confidence before tackling the right.
Step 1 — Establish your aortic landmark. Place your probe in a sagittal orientation in the left cranial abdomen and identify the aorta as a large, anechoic, pulsatile structure. This is your anchor point.
Step 2 — Locate the left kidney. Move laterally until the left kidney comes into view, then work medially back toward the aorta.
Step 3 — Find the cranial mesenteric artery. This vessel originates from the aorta and travels ventrally. It appears as a rounded cross-sectional structure when your probe is in a sagittal orientation relative to it.
Step 4 — Identify the renal artery hook. The left renal artery branches off the aorta caudal to the cranial mesenteric artery. The left adrenal gland sits in the space between these two vessel origins — cranial to the renal artery, caudal to the celiac and cranial mesenteric arteries.
Step 5 — Look for the peanut. Once you're in the right region, the left adrenal gland should appear as a discrete, hypoechoic, peanut-shaped structure lying against the lateral aspect of the aorta. Fan your probe gently and optimise your depth and gain. It is small — typically less than 1 cm in maximum thickness in a normal dog — so resist the temptation to over-interpret fat lobules or nearby lymph nodes.
Step-by-Step: Finding the Right Adrenal Gland in Dogs
This one requires more patience, and in some patients (particularly large or obese dogs) the overlying ribs and hepatic tissue can genuinely limit your window.
Step 1 — Scan the right cranial abdomen in a sagittal plane. Your target landmark is the caudal vena cava (CVC) in long axis. The CVC is recognisable as a compressible, non-pulsatile, anechoic vessel — larger in diameter than the aorta at this level.
Step 2 — Apply deliberate transducer pressure. This is a practical trick that works well: applying firm but gentle pressure over the CVC compresses the vessel slightly and helps bring the right adrenal into clearer view. The gland sits dorsolateral to the CVC and is closely associated with it.
Step 3 — Look between the last two intercostal spaces. The right adrenal is often best imaged from a lateral intercostal approach rather than a purely ventral window, particularly in larger dogs. Angling your probe cranially between the last intercostal spaces, with the patient in left lateral recumbency, can significantly improve your access.
Step 4 — Look for the arrowhead. The right adrenal, when visible, typically appears as a hypoechoic structure with a slightly irregular or comma-shaped outline, sitting dorsal or dorsolateral to the CVC. It tends to be slightly more compact than the left and may be partially obscured by the adjacent liver.
Step 5 — Use colour Doppler if needed. Activating colour Doppler to confirm the CVC and adjacent renal vasculature can help you orient yourself and narrow your search area considerably.
What Normal Looks Like
Once you find the glands, you need to know what you're looking at. Normal adrenal glands share a few consistent features:
Echogenicity: Both glands are hypoechoic relative to the surrounding retroperitoneal fat. The parenchyma is typically homogeneous, though a two-layer appearance representing cortex and medulla can sometimes be appreciated.
Size: In dogs, the most reliable measurement is the thickness (dorsoventral dimension) of the caudal pole, measured in the sagittal plane. Normal values in dogs generally fall between 3 and 7 mm in this dimension, with some variation by body weight. A caudal pole thickness exceeding 7–8 mm is considered suspicious. Note that body weight influences absolute measurements, and the adrenal-to-aorta ratio has been proposed as a more weight-independent reference in some studies. In cats, normal caudal pole thickness is reported up to approximately 4–4.3 mm.
Shape: Left — peanut or dumbbell. Right — comma or arrowhead. Both should have smooth, well-defined margins.
If you see all of this, you can confidently document normal adrenal glands and move on. That in itself is clinically useful information.
When Something Is Not Right: Key Abnormal Findings
Bilateral adrenomegaly — think pituitary-dependent hyperadrenocorticism (PDH)
In dogs with PDH (the most common form of Cushing's disease, accounting for around 80–85% of cases), the glands may be normal in size, bilaterally enlarged with a preserved shape, or show nodular hyperplasia. Bilateral caudal pole thickness exceeding 7–8 mm, particularly when accompanied by other ultrasound signs of Cushing's — a steroid-hepatopathy pattern in the liver, biliary sludge, or a distended bladder — should prompt further endocrine investigation.
Unilateral enlargement or mass — think adrenal-dependent hyperadrenocorticism or phaeochromocytoma
A unilateral adrenal mass with a contralateral gland that is normal or atrophied is highly suggestive of adrenal-dependent Cushing's. However, adrenal masses can also represent phaeochromocytomas (tumours of the adrenal medulla), non-functional adenomas, myelolipomas, carcinomas, or metastatic disease. Ultrasound alone cannot differentiate benign from malignant lesions, and a larger mass is statistically more likely to be malignant — masses exceeding approximately 3 cm carry a greater concern for malignancy or local invasion. Critically, always evaluate the CVC for signs of tumour thrombus, as right-sided adrenal tumours in particular have a well-documented tendency for vascular invasion.
Bilaterally small glands — think hypoadrenocorticism
Small adrenal glands (caudal pole thickness below approximately 3 mm) can be seen in dogs with spontaneous or iatrogenic hypoadrenocorticism. This is a useful supporting finding in the right clinical context, though not every Addisonian patient will have measurably small glands on ultrasound.
In cats specifically — watch for hyperaldosteronism
Primary hyperaldosteronism is increasingly recognised in middle-aged to older cats and typically presents with muscle weakness, hypokalemia, and systemic hypertension. The most common ultrasonographic finding is a unilateral adrenal mass — these can be substantial in size. Importantly, a normal-appearing contralateral gland does not exclude bilateral involvement. In cats with confirmed pituitary-dependent hyperadrenocorticism, bilateral adrenal enlargement may be seen, though some cases fall within reference size intervals.
The Honest Truth About Difficulty
It's worth being transparent here: some patients will defeat you, and that's not a reflection of your skill. Large dogs with generous retroperitoneal fat, deep-chested breeds, patients that won't stay still, or those with significant bowel gas — all of these make adrenal scanning harder. Even experienced radiologists acknowledge that the right adrenal in particular can be elusive.
What makes the difference over time is not raw talent — it's a reproducible method and enough repetition to build spatial confidence. Most practitioners who describe adrenal scanning as consistently achievable have done so by adopting the vessel-landmark approach described above, rather than searching randomly in the vicinity of the kidneys.
The practical implication? Start attempting adrenal glands on every abdominal scan you perform, not just on the high-index-of-suspicion Cushing's cases. Build your normal database. When you know what normal looks like in your hands, on your machine, in your patient population — the abnormal cases become significantly easier to identify.
A Note on Documentation
When you do image the adrenal glands, document them properly. Record the caudal pole thickness of both glands (in millimetres, sagittal plane), describe the echogenicity and shape, and note any asymmetry or focal lesions. If you cannot visualise one or both glands — which is a legitimate finding in some patients — record that too. A documented failed attempt is better than a scan report that simply omits the adrenals entirely, and it justifies referral for cross-sectional imaging if clinical suspicion is high.
Ready to Build This Into Your Practice?
The adrenal glands are just one of the structures we cover in depth on our Abdominal Ultrasound CPD course at Echo Vet Solutions — alongside the liver, spleen, kidneys, GI tract, lymph nodes, pancreas, and major abdominal vessels. The course is delivered in your own practice, on your own machine, at your own pace. No travel. No generic lecture-room scanning. Just hands-on, bespoke training tailored to where you actually are with ultrasound right now.
Whether you're just starting out with abdominal scanning or you're confident with the major organs and want to tackle the trickier structures — adrenals, pancreas, lymph nodes, guided sampling — we have a session to match.
Or if you'd prefer to have a conversation first, get in touch via our Contact page — we're always happy to discuss what would work best for your team.
Summary: Key Takeaways
The adrenal glands are small, deep, and hypoechoic — but reliably findable with a vessel-based landmark approach
The left adrenal gland (peanut-shaped, between cranial mesenteric and renal arteries) is consistently easier to locate than the right
The right adrenal gland (comma/arrowhead-shaped) abuts the CVC — use the vena cava, apply probe pressure, and consider an intercostal approach
Normal caudal pole thickness: approximately 3–7 mm in dogs; up to ~4.3 mm in cats
Bilateral adrenomegaly suggests PDH; unilateral mass requires careful characterisation including vascular assessment
Feline adrenal scanning is similar in approach; hyperaldosteronism is the primary pathological consideration in cats
Consistent practice on every abdominal scan — not just Cushing's suspects — is the fastest route to confidence
References:
Barthez PY, Nyland TG, Feldman EC. Ultrasonography of the adrenal glands in the dog, cat, and ferret. Vet Clin North Am Small Anim Pract. 1998;28(4):869–885.
Combes A, Pey P, Paepe D, et al. Ultrasonographic appearance of adrenal glands in healthy and sick cats. J Feline Med Surg. 2013;15(5):445–457.
Garcia ED. Ultrasonography of the adrenal glands. Today's Veterinary Practice. 2017.
Griffin S. Feline abdominal ultrasonography: what's normal? what's abnormal? The adrenal glands. J Feline Med Surg. 2021;23(1):41–56.
Nyland TG, Mattoon JS (eds). Small Animal Diagnostic Ultrasound, 3rd edition. Saunders Elsevier.
Soulsby SN, Holland M, Hudson JA, Behrend EN. Ultrasonographic evaluation of adrenal gland size compared to body weight in normal dogs. Vet Radiol Ultrasound. 2015;56(3):317–326.
