Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Three The Abd omen 267
Fig. 3-19 Longitudinal sonograms of the left and right kidney and
ovary of a 9-year-old female mixed breed dog with a history of chronic
pericardial effusion. The ovaries can be identified as oval hypoechoic
structures (arrows) caudal to the kidneys. The ovaries appear slightly
enlarged but their architecture is normal. Diagnosis: Normal ovaries.
kidney in a longitudinal plane and then moving or rolling the transducer toward the midline
until the aorta is identified. The adrenal gland will be located adjacent to the left lateral aspect
of the aorta just cranial to the origin of the left phrenicoabdominal artery. An alternative
method of finding the left adrenal gland consists of imaging the aorta transversely and tracing
it caudally to the origin of the phrenicoabdominal artery just cranial to the left kidney. A
third method of locating the adrenal gland is to image the ipsilateral kidney in a dorsal plane
with the aorta in the same plane as the kidney. Fanning the transducer dorsally and ventrally
usually will reveal the left adrenal gland. The adrenal gland may be oriented slightly oblique
to the aorta; therefore the transducer must be manipulated until the complete adrenal gland
is identified in a longitudinal plane. The adrenal gland frequently is masked by overlying
intestines, and gentle pressure using the transducer may be required to displace these intestinal
loops away from it. 44 The right adrenal gland may be imaged by identifying the caudal
vena cava in a longitudinal plane and moving the transducer toward the right kidney at the
level of the cranial pole. The vena cava may be imaged in the transverse plane and followed
cranially and caudally at the level of the kidney until a cross-section of the adrenal gland is
found. Placing the transducer on the right dorsolateral abdomen in a longitudinal orientation
and identifying the vena cava and the aorta helps to locate the right adrenal gland, which
will be in the plane of the caudal vena cava. Another method of locating the right adrenal
gland is to image the ipsilateral kidney in a dorsal plane, with the caudal vena cava in the same
plane as the kidney. Fanning the transducer dorsally and ventrally usually will reveal the right
adrenal gland between the cranial pole of the left kidney and the vena cava. In most dogs, the
left adrenal gland appears bipartite or peanut shaped, with an echo intensity similar to renal
medulla. In some patients, a distinction can be made between the hypoechoic cortex and
hyperechoic medulla (Fig. 3-20). The cranial and caudal poles are often asymmetric. The
imaged size of the normal canine adrenal glands varies considerably as reported by various
authors. 41,42,45 Currently we suggest that a maximal diameter of about 5 to 6 mm and a maximal
length of about 20 mm be considered as a useful guideline for normal dogs. One study
evaluated the use of instilling normal saline into the peritoneal cavity to improve visualization
of the adrenal glands and found it was not very helpful. 19