Ultrasound of the Adrenal Glands
Alain Giroux, DVM, MSc, DACVR
Introduction
The identification of the adrenal glands is a process that requires experience and is a skill that can only be master
over time. The approach for localizing and identifying the adrenal glands is based on the anatomy of the vessels in
close proximity.
Although this technique is more difficult then utilizing the kidneys alone for localisation, it is more accurate and
when mastered, it will provide easy identification of the adrenal glands in 95 % of the cases.
The secret is to review the anatomy (Fig. 1AD) again and again.
Anatomy of the Adrenal Glands
Figure 1 AD: Adrenals and Vessels Anatomy
Vessels: Aorta (AO)
Caudal vena cava (CVC)
Celiac and cranial mesenteric artery
Right (RK) and left kidney (LK)
Right (RA) and left adrenal (LA) gland
The phrenico-abdominal vessels are seen on occasion especially if color Doppler is utilized or there is pathology
involving their lumen. They provide the blood supply to the adrenal glands.
The renal veins are not always visualized. The renal arteries can be seen as branch of the aorta often in a similar
plane to the celiac and cranial mesenteric arteries.
The renal veins are often better visualized if any cause for venous congestion, such as hepatic hypertension, is
present.
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Ultrasonographic Anatomy
In some cases the adrenal glands can be easily identified without localising the mains vessels. However, in most
cases, especially if the adrenal glands are normal or small, the vessels will be needed to identify the location of the
adrenal glands. The principle in identifying the adrenal glands is very similar for dogs, cats and ferrets.
Please note that this technique is the one I utilized. It is not the only way adrenals can be identified but I find the
most accurate and successful.
Also, you will find that good amount of pressure will be needed in some cases to get good visualization of the right
adrenal. This is mostly necessary in large dogs or tense patients. In small dogs or cats, applying too much pressure to
the right side will reduce the diameter of the CVC and will make identification difficult.
For the Right Adrenal (Fig. 2 and 3 AD):
Place the patient in a dorsal recumbency but with the sternum rotated 30 degrees towards the left side.
Place the transducer just caudal to the right costal arch and aim dorsally and towards the right of the mid-line
(spine).
Approach the adrenal by first locating the cranial pole of the right kidney.
After finding the cranial pole, angled the transducer more towards the mid-line, medial to the kidney.
You may find the right adrenal gland right away by repeating this a few times.
If not seen with this fanning, proceed to find the CVC and AO, which should run parallel to the spine and to each
other. They are also running in this plane slightly from caudo-ventral to cranio-dorsal direction.
After finding the CVC (always remain at the level or slightly cranial the cranial pole of the right kidney), fan back
very minimally laterally and the right adrenal should be located lateral to the CVC and slightly dorsal.
You will find that most of the time the adrenal can be seen in close contact with the CVC and you may see both
structures in the same scanning plane. Also the celiac and cranial mesenteric arteries can be seen from the right
side. The right adrenal is often slightly cranial to them or projected in between them.
Figure 2 AD: Normal Right Adrenal Gland
Figure 3 AD: Right Adrenal Scanning
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For the Left Adrenal (Fig. 4, 5 and 6 AD):
-Place the patient in a dorsal recumbency but with
the sternum rotated 30 degrees towards the right side.
-Place the transducer in the mid-abdomen and aim
dorsally and towards the left of the mid-line (spine).
-Approach the adrenal by first locating the cranial pole
of the left kidney.
-After finding the cranial pole, angled the transducer
more towards the mid-line, medial to the kidney.
-You may find the left adrenal gland right away by
repeating this a few times.
-If not seen with this fanning, proceed to find the aorta (AO),
which should run parallel to the spine.
-After finding the AO (always remain at the level
or slightly cranial the cranial pole of the left kidney),
fan back very minimally laterally and coming off the
AO , the celiac, cranial mesenteric and left renal
arteries can be seen ( Figure 6 AD).
-In between the cranial mesenteric and renal artery, the
left adrenal will be located.
-The left adrenal should be located lateral to the AO
and slightly ventral.
Figure 5 AD: Left Adrenal and Surroundings Vessels
Figure 4 AD: Normal Left Adrenal Gland
Figure 6 AD: Left Adrenal Scanning
Advanced scanning note: This following hint can be confusing into locating the adrenals. I do not recommend
placing too much effort into utilizing it, until you can easily recognized the main vessels (CVC and OA).
Hint: Although the celiac and cranial mesenteric arteries are located on the left side, when looking for the right
adrenal, by fanning towards the left of mid-line you may be able to see celiac and cranial mesenteric arteries. This
can help to locate the cranial and caudal level of the right adrenal gland. In general the right adrenal will be seen in a
different plane but at a level slightly cranial to both vessels or in between them.
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Normal Adrenal Ultrasound Anatomy:
With ideal conditions and with high-resolution transducer (7.5 to 10 MHz) you will be able to see the cortex and
medulla of the adrenals (Fig. 7 AD). The right adrenal has a more wedge shape appearance (Fig. 2 AD). The left
adrenal (Fig. 4 AD) is more of peanut shape.
With any transducer you will be able to see the:
-Cranial and caudal poles
-Celiac and cranial mesenteric arteries
Figure 7 AD: Adrenal Cortex and Medulla
Figure 8 AD: Adrenal Poles
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Adrenals Abnormalities
The abnormal adrenals are obviously easier to seen if enlarged. If smaller than normal, you may have to search
longer. In dogs, the normal adrenal thickness is in between 4 and 8 to 9 mm in thickness. The normal length
remains to determine and we do not measure it in most case unless there is a mass present. In cats, the normal
adrenal thickness is in between 2 and 4 mm in thickness. The adrenal glands tend to get larger in geriatric patient.
You should also be aware that the normal thickness is still a subject of debate. Adrenal size will vary with patient
size, age, and time of the day! No definitive weight relationship is well established. Some authors advocate 10 mm
for normal thickness in dogs. I am using 8 mm at this time for upper normal limits. The measurements should be
performed at the level of the widest portion of each pole.
Multiple criteria’s are important in the assessment of their size:
-Unilateral Symmetrical Enlargement
-Asymmetrical Unilateral Enlargement
- Bilateral Symmetrical Enlargement
-Bilateral Asymmetrical Enlargement
Note: Symmetry is relative to the cranial and caudal pole of one adrenal.
Figure 10 AD: Adenocarcinoma
Adrenal Benign Disease:
-Adenoma
-Hyperplasia (Fig 9 AD)
-Cyst
-Hematoma
Adrenal neoplastic infiltrate:
-Adenocarcinoma (Fig. 10 AD)
-Pheochromocytoma (Fig. 11 AD)
-Metastatic neoplasms
-Infectious:
Abscess
Figure 11 AD: Pheochromocytoma
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