Case file: LIBBY
12-year-old spayed female toy poodle weighing 5.3 lb (2.4 kg)
Patient history and initial diagnostic workup
Libby was presented to her primary care veterinarian for a dental prophylaxis. Libby also had a six-month history of panting,
polyuria, polydipsia, and recurrent ear infections. Physical examination before the dental procedure revealed a swelling in
Libby's perineal region, and the veterinarian subsequently diagnosed a left perineal hernia. The dental prophylaxis was rescheduled
for a later date, and Libby was referred to the Mississippi State University College of Veterinary Medicine (MSU-CVM) for
Todd M. Archer, DVM, MS, DACVIM
On presentation to MSU-CVM, Libby was bright and alert. The left perineal hernia was noticeable and was easily reduced. Her
abdomen appeared distended, but abdominal palpation revealed no abnormalities. The results of a serum chemistry profile revealed
mild increases in alanine aminotransferase (136 U/L; reference range = 10 to 90 U/L) and alkaline phosphatase (153 U/L; reference
range = 11 to 140 U/L) activities. Libby's urine specific gravity was 1.019. Based on these results and the history of panting,
polyuria, polydipsia, and recurrent infections, a workup for hyperadrenocorticism was performed.
Adrenal function test results
Results of an adrenocorticotropic hormone (ACTH) stimulation test revealed a baseline cortisol concentration of 8.5 μg/dl
(reference range = 1.4 to 5 μg/dl) and a one-hour post-ACTH cortisol concentration of 24.8 μg/dl (reference range = 5.5 to
20 μg/dl). These results confirmed hyperadrenocorticism.
Abdominal imaging was performed to differentiate pituitary-dependent hyperadrenocorticism (PDH) from an adrenal tumor. The
abdominal radiographic findings were unremarkable. Abdominal ultrasonography revealed normal-sized and symmetrical adrenal
glands and no evidence of an adrenal mass. Also noted were a single hepatic lesion and a single splenic lesion, as well as
a gallbladder mucocele in the early stages of development. Ultrasound-guided fine-needle aspirates of the lesions within the
liver and spleen were obtained. A thoracic radiographic examination was also performed, and the findings were unremarkable.
Libby's abnormal ACTH stimulation test results along with the abdominal ultrasonographic findings provided a working diagnosis
Cytologic examination of the hepatic and splenic lesion aspirates showed mild extramedullary hematopoiesis, likely consistent
with regenerative nodules. The liver aspirates also showed evidence of vacuolar degeneration, a finding consistent with hyperadrenocorticism.
*The dog in the photograph is not Libby, the dog described in this article.