DIAGNOSTIC IMAGING
Ultrasonographic Assessment
Of The Adrenal Glands In Dogs And Cats
Dr Nicki Cassel BSc BVSc MMedVet (Diagnostic Imaging) DipECVDI
VET IMAGING SPECIALISTS
[email protected]
VetImaging
Specialists
Introduction
Although ultrasound is less sensitive than computed
tomography (CT) in assessing the adrenal glands it is
the preferred primary method of assessment due to
its accessibility in veterinary practice.
The indications to ultrasound the adrenal glands are
largely to support a presumptive diagnosis of hyperadrenocorticism and to further differentiate between
adrenal-dependant and pituitary-dependant hyperadrenocorticism. Further indications include investigating peritoneal or dorsal abdominal masses, hypertension and other clinical signs which may be related
to phaeochromocytoma and to search for metastasis.
A
Normal Ultrasonographic Assessment
Patients can either be positioned in dorsal or lateral
recumbency. It is essential to use a high frequency
transducer to visualise the adrenal glands and a thorough knowledge of the regional vasculature is required to locate the adrenal glands. 1,2
B
With the patient in right lateral recumbency, the left
adrenal gland can be visualised by positioning the
transducer caudal to the last rib and ventral to the
lumbar muscles at the level of the left kidney. Utilising
this ultrasound window, the aorta should be seen running in a cranio-caudal direction and will be the closer
of the two large vessels. The left renal artery can be
seen exiting the aorta directed caudally where after it
immediately deviates cranially to reach the renal hilus.
C
The adrenal gland is located between the aorta and
the left kidney, cranial to the hook made by the renal
artery (Figure 2 B).1
With the patient positioned in left lateral recumbency,
and with the transducer in a similar position as on the
contralateral side, the caudal vena cava and right kidney are located as landmarks to visualise the right adrenal gland. The right adrenal gland abuts the caudal
vena cava. The right adrenal gland is more challenging to find than the left gland.1,2
Figure 1: Normal ultrasound appearance of the left (A) and right
(B) canine adrenal gland of a medium sized dog. They are slender elongated homogenously hypoechoic structures. (C) is
the right adrenal gland from a Yorkshire terrier showing clear
cortico-medullary distinction sometimes seen in normal adrenal glands.
A similar approach is used when locating the adrenal glands in feline patients, however the glands are
consistently more cranially located along the main
abdominal vessels, lying just cranial to the cranial pole
of each respective (left and right) kidney. 2
The left adrenal gland is peanut shaped in smaller dogs
and elongated and slender in medium to large breed
dogs. (Figure 1 A and B) The right adrenal gland has
been reported to have an “arrow” shape or L-shaped.
The glands are typically uniformly hypoechoic how-
Issue 06 | DECEMBER 2015 | 13