Ultrasonographic detection of adrenal gland tumors in two ferrets
Janette Ackermann, DVM; James W. Carpenter, MS, DVM; Cynthia P. Godshalk, DVM, MS; Craig A. Harms, DVM
· Hyperadrenocorticism is recognized as a com- mon medical condition in middle- to older-aged ferrets.
· Diagnosis of adrenocortical tumors in ferrets, using adrenocorticotropic hormone stimulation or dexamethasone suppression test results, is unreliable. Ultrasonography can be a viable al- ternative to laparotomy for the detection of this disorder.
· Ultrasonography can be used to diagnose ad- renal gland tumors in ferrets. The diagnosis should be confirmed by surgical excision and histologic examination of the adrenal gland.
A 4-year-old spayed female ferret (Mustela puto- rius furo; ferret 1) was admitted for persistent signs of estrus. Physical examination revealed only pronounced vulvar swelling. Hematologic and se- rum biochemical values were within reference range limits. Remnant or ectopic ovarian tissue or adrenal gland neoplasia was suspected. Abdominal ultrasonography was performed, using 7.5-MHz linear and sector transducers.ª A large right adrenal gland (6.8 × 5.5 mm) was detected; reference range limits for adrenal glands of ferrets is ≤ 2.0 mm.1 Evidence of ovarian tissue was not observed.
Neoplasia of the right adrenal gland was sus- pected, and surgical excision and histologic evalu- ation of the gland were performed. Histologically, the adrenal gland consisted of sheets of closely spaced polygonal cells of various sizes with a thin fibrovascular stroma. Cells had indistinct borders, moderate to abundant vesicular eosinophilic cyto- plasm, various sized pleomorphic vesicular nuclei, and prominent nucleoli. A few mitotic cells were detected, and only a thin rim of normal-appearing adrenal cortical tissue remained. The adrenal cap- sule was intact. Histologic diagnosis was carcinoma of the right adrenal cortex.
Five months after surgery, the owner reported the ferret to be clinically normal. Further signs of estrus had not been observed.
A 7-year-old castrated male ferret (ferret 2) was referred because of a 6-month history of alopecia
From the Department of Clinical Sciences, College of Vet- erinary Medicine, Kansas State University, Manhattan, KS 66506. Dr. Harms’ present address is College of Veterinary Med- icine, North Carolina State University, Raleigh, NC 27606.
The authors thank Drs. D. Bruyette and G. Kennedy for tech- nical assistance.
Address reprint requests to Dr. Carpenter.
aAcuson 128XP, Acuson Corp, Mountain View, Calif.
that was nonpruritic. The alopecia had started on the head and had progressed caudally. Examination of 2 specimens of skin scrapings by the referring veterinarian did not reveal external parasites. Clin- ical improvement was not seen despite treatment with medicated shampoos and flea-control prod- ucts and administration of 0.2 mg of triamcinolone acetonide,b IM. Although 2 months prior to exam- ination the ferret had had several episodes of post- prandial vomiting, the owner reported that the ferret’s appetite, activity, weight, patterns of uri- nation, and water consumption had remained un- changed.
Physical examination of the ferret revealed bi- laterally symmetric alopecia of the dorsum, which was most severe on the caudal half of the body. Parasites, erythema, or other lesions were not ob- served on the ferret’s skin, except for mild dry scaly seborrheic skin. The skin was thin and bruised eas- ily, which is a common clinical manifestation of hyperadrenocorticism in other animals. A 1-cm, freely movable mass was palpable in the subcuta- neous tissues of the left inguinal area.
A presumptive diagnosis of hyperadrenocorti- cism was made, although the list of differential di- agnoses for the cause of the alopecic condition also included hypothyroidism, hyperestrogenism, so- matostatin deficiency, and hepatic disease. Differ- ential diagnoses for the inguinal mass included neoplasia and peripheral lymphadenopathy/hy- perplasia. Hematologic examination, serum bio- chemical analysis, abdominal radiography and ul- trasonography, and fine-needle aspiration of the inguinal mass were performed. Analysis of hema- tologic and serum biochemical analysis results re- vealed anemia (PCV, 26%; reference range, 42 to 55%; RBC count, 5.2 × 106 cells/mm3; reference range, 7 to 10 × 106 cells/mm3; and hemoglobin concentration, 9.0 g/dl; reference range, 15 to 17 g/dl) and hypoglycemia (60 mg of glucose/dl; ref- erence range, 100 to 207 mg/dl).2 Radiography revealed splenomegaly and a 5 × 15-mm soft-tis- sue opacity craniomedial to the left kidney (Fig 1). Mineralization was not evident. In 1 report,3 half of the adrenal gland tumors in dogs had radio- graphic evidence of internal mineralization, a find- ing that was considered useful in detecting adrenal gland tumors radiographically. Ultrasonography of
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ferret 2 revealed a large (11.5 mm in diameter) left adrenal gland (Fig 2).
Exploratory laparotomy was performed. Pan- creatic hyperplasia or neoplasia was suspected on
the basis of the hypoglycemia. Blood glucose con- centrations were monitored periodically during sur- gery. Twice during surgery, 1 ml of 10% dextrose solution was given IV. Prednisolone sodium succin- atec (10 mg/kg of body weight, IV) also was admin- istered.
The left adrenal gland was located in a normal position, but was large (20 × 10 mm), dark black, and well-encapsulated (Fig 3). Multi-focal nod- ules, 3 to 5 mm in diameter, were located diffusely throughout the pancreas, and a 5-mm whitish-tan nodule on the visceral surface of the left lateral lobe of the liver was identified. Excisional biopsies were obtained from 2 pancreatic nodules and the ingui- nal mass.
Histologic examination of the adrenal gland re- vealed round to oval pleomorphic, commonly ve- siculated, cells that contained single prominent nuclei. Cells with indistinct borders were arranged in sheets. Adrenal gland adenocarcinoma was di- agnosed. It was difficult to differentiate between ad- enocarcinoma of the cortex and medulla. Histologic examination of the inguinal mass revealed a malig- nant spindle-cell neoplasm that was suggestive of a hemangiopericytoma. Pancreatic nodules consisted of nodular hyperplastic cells with no evidence of neoplasia.
Clinical signs, including bilaterally symmetric alopecia that was nonpruritic and thin skin and ex- cessive bruising consistent with adrenal gland tu- mors, for 1 of these ferrets were similar to those reported for other mammals with adrenal gland tu- mors. Although muscle weakness, lethargy, poly- phagia, polyuria, and polydipsia commonly are seen in dogs and cats with adrenal gland tumors,4 they were not noticed in the ferrets of this report; however, it was indicated in 1 report that polyuria and polydipsia were observed in only 8% of ferrets
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with adrenocortical tumors.5 Obesity and hepato- megaly are seen in dogs with hyperadrenocorti- cism, but were not observed in the ferrets of this report. In ferret 1, persistent signs of estrus (vulvar swelling and serous to mucopurulent vaginal dis- charge) were seen, but resolved after removal of the adrenal gland tumor. Vulvar enlargement is a com- mon finding in female ferrets with hyperadreno- corticism.5 Lymphopenia and eosinopenia in ferrets with adrenocortical tumors are common because of high glucocorticoid concentrations,6,7 but were not detected in these 2 ferrets.
In the past, difficulties have been encountered in definitively diagnosing adrenocortical tumors in ferrets by means of ACTH stimulation or dexa- methasone suppression tests. Although cortisol production is rarely high in ferrets with hyperad- renocorticism, other factors, such as season, stress, trauma, and disease, also affect cortisol concentra- tions in ferrets. Ferrets are classified as a steroid- resistant species, because they do not respond to the dexamethasone suppression test in a manner similar to other mammals, such as dogs.1,8,9 Results of a dexamethasone sodium phosphate (0.1 mg/kg, IM) suppression test performed on ferret 2 were in- conclusive for hyperadrenocorticism. Procedures that have been used to diagnose adrenal neoplasias in dogs include computed tomography and scintig- raphy, which are expensive and not readily availa- ble to general practitioners.10-12 For the ferrets of this report, ultrasonography was diagnostic and re- vealed the large adrenal glands; computed tomog- raphy or scintigraphy were not necessary.
When using ultrasonography for examination of the adrenal glands of ferrets, the entire ventral abdomen should be clipped, including an area that extends from 1 cm cranial to the xiphoid process caudally to the inguinal area and laterally to a point midway between the sternum and vertebral bodies. The area between the cranial pole of the kidney and the caudal vena cava should be searched to locate the adrenal glands. Portions of the spleen and transverse and descending colons may be in this area, and they should be positively identified by shifting the position of the transducer to obtain im- ages in more than 1 plane of section. Adrenal glands appear as small, flattened, triangular masses of moderate echogenicity. Unilateral enlargement of the adrenal glands is indicative of adrenal gland hyperplasia or neoplasia.13 To determine the sur- gical prognosis,14 it is important to examine the caudal vena cava for evidence of extension of the adrenal gland into the lumen or the tissues around the vein.14 Variations in tissue echogenicity are commonly seen in normal adrenal glands of human beings, and, therefore, are not indicative of abnor- malities. Abnormalities of shape and size are more accurate than variations in tissue echogenicity for the detection of adrenal gland disease in dogs.1,10,15
These observations may be true for ferrets as well, and variations in tissue echogenicity should not be used as the sole indication for surgical intervention. In dogs, variations in echogenicity cannot be used to differentiate the type of tumor, such as adrenal carcinoma, adenoma, or pheochromocytomas, from areas of necrosis or hemorrhage in adrenal glands.
Improvements in ultrasonographic equipment have allowed the observation of adrenal glands in many species of mammals, including ferrets. Al- though a single criterion cannot be used to differ- entiate benign from malignant neoplasms, ultraso- nography is a useful tool to detect morphologic abnormalities of adrenal glands and to examine other abdominal organs for evidence of metastasis of malignant tumors.1,10 Ultrasonography is a non- invasive diagnostic method that is an alternative to laparotomy for the detection of adrenal gland dis- ease in ferrets.
References
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