Internal Medicine Case of the Month: Diagnosis and Preoperative Management of a Malignant Adrenal Tumor


Lucy is a 12 year old spayed female mixed breed dog that presented to the PVESC Internal Medicine Service for additional evaluation of a left adrenal mass.

Lucy developed clinical signs, including an increase in thirst and urination, in October 2023. Initial diagnostics were performed by the referring veterinarian. Lucy’s chemistry profile showed a mixed elevation in her liver enzymes (ALT 235, ALP 296, GGT 26). A complete blood count was unremarkable. Lucy’s total T4 was within normal limits. A urinalysis showed dilute urine without evidence of infection or inflammation. She later had her blood pressure measured. In January 2024, prior to starting anti-hypertensive therapy, Lucy’s blood pressure was found to be markedly elevated (> 200 mmHg). Enalapril was started as an anti-hypertensive. Lucy then had an abdominal ultrasound with her primary veterinarian that showed a cranial pole left adrenal mass. She was referred at this time.

Lucy first visited PVESC in March 2024. A recheck chemistry profile showed progressive elevations in her liver values (ALP 672, ALT 260, GGT 51). Dr. Shoelson, one of the PVESC internists, repeated Lucy’s ultrasound. A left, cranial pole adrenal mass that measured up to 2.94cm in diameter was appreciated. There was no evidence of vascular invasion. A sonographic image of the left adrenal mass is provided below.

Lucy had mild enlargement of her liver with some hyperechoic nodules distributed throughout. Hyperechoic nodules (likely myelolipomas) were noted in the spleen as well.

Adrenal tumors can be functional/hormone-secreting or non-functional. They can also be benign or malignant. An adrenal tumor that measures greater than 2 cm in diameter or that is invading into local vasculature is more likely to be malignant. The two most common malignant adrenal tumors are adrenocortical carcinomas and pheochromocytomas (which arise from the adrenal medulla and produce excess catecholamines). Similar clinical signs and biochemical changes can be seen with functional adrenocortical carcinomas and pheochromocytomas. Given Lucy’s cholestatic liver enzyme elevation and her increased thirst and urination, both classic changes seen with hyperadrenocorticism, we first elected to perform an ACTH stimulation test. Lucy’s ACTH stimulation test supported a diagnosis of hyperadrenocorticism. Our index of suspicion for a functional, adrenocortical tumor increased.

Lucy’s owner expressed an interest in moving forward with surgery. To stabilize her prior to surgery, we continued with anti-hypertensive therapy (enalapril) and also began treating her hyperadrenocorticism with twice daily trilostane (Vetoryl). Lucy’s clinical signs improved. A recheck chemistry profile showed improved liver enzyme values, and a follow up ACTH stimulation test was suggestive of ideal hyperadrenocorticism control. Lucy was then referred to Dr. Maxwell Bush to discuss minimally invasive laparoscopic adrenalectomy. Additional information on Lucy’s surgical treatment can be found in this Surgery article.

Authored by: Adam Shoelson, DVM, DACVIM (Small Animal Internal Medicine)