Page 920 - Small Animal Internal Medicine, 6th Edition

892 PART VI Endocrine Disorders

adrenalectomy is not performed. Long-term medical man- the mass, and the client’s desires and willingness to pursue
agement is designed to control excessive catecholamine the problem. The first consideration is to verify an adrenal
VetBooks.ir secretion, not to lessen the risk of local invasion or metasta- mass exists by repeating the abdominal ultrasound. An
adrenal tumor should be suspected when there is loss of the
sis of the tumor. Phenoxybenzamine at an initial dosage of
0.50 mg/kg q12h is recommended. The dose is gradually
regardless of size, there is asymmetry in shape and size
titrated upward until clinical signs are controlled or clinical typical shape of the gland (i.e., the gland looks like a mass)
signs suggestive of hypotension occur. between the affected adrenal gland and the contralateral
adrenal gland, or there is infiltration of the mass into the
Prognosis phrenicoabdominal vena, vena cava, or surrounding soft
The prognosis depends in part on the size of the adrenal mass, tissues.
the presence of metastasis or local invasion of the tumor into A bulbous enlargement or “nodule” of the cranial or
adjacent blood vessels or organs (e.g., kidney), avoidance of caudal pole of an otherwise recognizable adrenal gland is a
perioperative complications if adrenalectomy is performed common finding in older dogs and is often misinterpreted
(i.e., hypertension, cardiac arrhythmias, respiratory distress, as an adrenal mass or tumor (Fig. 50.20). Bulbous enlarge-
and hemorrhage), and the presence and nature of concur- ments are typically less than 1.5 cm in maximum width and
rent disease. Surgically excisable tumors carry a guarded to the contralateral adrenal gland is usually normal in size and
good prognosis. Survival time in our dogs that underwent shape. A bulbous enlargement is usually not neoplastic or
adrenalectomy and survived the immediate postoperative functional (i.e., autonomously secreting a hormone). Histo-
period ranged from 2 months to longer than 3 years. If met- logic examination usually reveals normal tissue, inflamma-
astatic disease is not present, perioperative complications tion, granuloma or clinically irrelevant benign tumor (e.g.,
are prevented, and serious concurrent disease is not present, myelolipoma). Less commonly, cortical tumors and pheo-
the dog has the potential to live a significantly longer time chromocytomas in the early stages of development have been
(i.e., longer than a year). Treatment with an α-adrenergic identified. If there are no clinical signs or findings on phys-
blocking drug before surgery and the involvement of an ical examination and routine blood and urine tests do not
experienced anesthesiologist and surgeon with expertise in support a functional adrenal tumor, a conservative approach
adrenal surgery help to minimize potentially serious periop- centered around periodic monitoring with ultrasound, ini-
erative complications associated with anesthesia and digital tially at monthly intervals, for changes in size of the nodule
manipulation of the tumor. Medically treated dogs can live and appearance of the adrenal gland is recommended. If
longer than 1 year from the time of diagnosis if the tumor is the adrenal mass has not changed in size after 3 months,
relatively small (<3 cm maximum width), vascular invasion the clinician can increase the time interval between ultra-
is not present, and treatment with an α-adrenergic block- sound evaluations recommended. However, if the adrenal
ing drug is effective in minimizing the deleterious effects nodule is increasing in size, changing in appearance, com-
of episodic excessive catecholamine secretion by the tumor. pressing or infiltrating surrounding blood vessels or soft
Most dogs die or are euthanized because of complications tissues, or clinical signs affiliated with an excess of cortisol,
caused by excessive catecholamine secretion, complications catecholamines, or aldosterone develop, adrenalectomy may
caused by tumor-induced venous thrombosis, or complica- be warranted.
tions caused by invasion of the tumor or its metastases into Adrenalectomy is the treatment of choice if the mass is
surrounding organs. suspected to be malignant. Unfortunately, it is not easy to
determine whether an adrenal mass is neoplastic and malig-
nant or benign before surgical removal and histopathologic
INCIDENTAL ADRENAL MASS evaluation. Guidelines to suggest malignancy include size of
the mass, infiltration of the mass into surrounding organs
Ultrasonography has become a routine diagnostic tool for and blood vessels, and identification of additional mass
the evaluation of soft tissue structures in the abdominal lesions with abdominal ultrasound and thoracic radiographs.
cavity. One consequence of abdominal ultrasonography is The bigger the mass, the more likely it is malignant and the
the unexpected finding of a seemingly incidental adrenal more likely metastasis has occurred, regardless of findings
mass. Recent retrospective studies identified an unexpected on abdominal ultrasound and thoracic radiographs. Cyto-
adrenal lesion in 4% of 3478 dogs undergoing abdominal logic evaluation of specimens obtained by ultrasound-guided
ultrasound (Cook et al., 2014) and 9% of 270 dogs undergo- fine-needle aspiration of the adrenal mass may provide guid-
ing abdominal CT (Baum et al., 2016). Several factors deter- ance regarding malignancy and origin of the mass (i.e.,
mine the aggressiveness of the diagnostic and therapeutic adrenal cortex versus medulla).
approach to an adrenal mass, including the severity of con- An adrenal tumor may secrete a hormone or be non-
current problems, the original reason for performing functional. Excessive secretion of cortisol, catecholamines,
abdominal ultrasound, the age of the dog or cat, the likeli- aldosterone, progesterone, and steroid hormone precursors
hood that the mass is hormonally active, the likelihood that has been documented in dogs and cats (see Table 50.6). The
the mass is a malignant tumor, the size and invasiveness of most common functional adrenal tumors secrete cortisol