Ultrasonography Criteria for Differentiating ACTH Dependency from ACTH Independency in 47 Dogs with Hyperadrenocorticism and Equivocal Adrenal Asymmetry

Abstract

Background: Adrenal ultrasonography (US) in dogs with hyperadrenocorticism (HAC) is commonly used to distinguish adrenocorticotropic hormone (ACTH)-independent (AIHAC) and ACTH-dependent hyperadrenocorticism (ADHAC). To date, no cut-off values for defining adrenal atrophy in cases of adrenal asymmetry have been determined. Given that asymmetrical hyperplasia is sometimes observed in ADHAC, adrenal asymmetry without ultrasonographic proof of adrenocortical tumor such as vascular invasion or metastasis can be equivocal.Objective: The purpose of this study was to compare adrenal US findings between cases of ADHAC and AIHAC in dogs with equivocal adrenal asymmetry (EAA), and to identify useful criteria for their distinction.Animals: Forty dogs with EAA were included. Methods: Ultrasound reports of HAC dogs with adrenal asymmetry without obvious vascular invasion or metastases were reviewed. Dogs were classified as cases of ADHAC (n 5 28) or AIHAC (n 5 19), determined by plasma ACTH concentration. The thickness, shape, and echogenicity of both adrenal glands and presence of adjacent vascular compression were compared between AIHAC and ADHAC groups.Results: The maximal dorsoventral thickness of the smaller gland (SDV) ranged from 2.0 to 5.0 mm in AIHAC and from 5.0 to 15.0 mm in ADHAC. The 95% confidence intervals for estimated sensitivity and specificity of a SDV cut-off set at 5.0 mm in the diagnosis of AIHAC were 82-100 and 82-99%, respectively. Other tested US criteria were found to overlap extensively between the 2 groups, precluding their usefulness for distinction.Conclusion and Clinical Importance: In EAA cases, an SDV 5.0 mm is an appropriate cut-off for AIHAC ultrasonographic diagnosis.

Ultrasonographic features of adrenal gland lesions in dogs can aid in diagnosis

“…Consistent with previous findings, adrenocortical carcinomas were generally unilateral, with an equal distribution between sides [22], with atrophy of the contralateral gland in 4 cases, suggesting a hormone-dependent neoplasia, as described elsewhere [2]. In agreement with previous studies [12] cortical adenomas were macroscopically characterized by a nodular pattern.…”

“…Among the methods of diagnostic imaging, ultrasound is considered a relatively rapid, non-invasive, inexpensive and reliable modality to evaluate suspected adrenal masses [2]. Beginning in the mid-1990s, ultrasound imaging has become a widely used diagnostic tool in veterinary medicine.…”

Epidemiology of hyperadrenocorticism among 210,824 dogs attending primary‐care veterinary practices in the UK from 2009 to 2014

“…However, this distinction between PTHAC and ATHAC was infrequently recorded in the EPRs of the current study. The LDDST can differentiate PTHAC from ATHAC in approximately two-thirds of cases and, with specialist equipment and operator skills, adrenal ultrasonography has a high diagnostic sensitivity and specificity (82-100% and 82-99%, respectively) for the diagnosis of ATHAC (Behrend et al, 2015, Benchekroun et al, 2010. Increased awareness of the importance of this differentiation step should improve the management of hyperadrenocorticism-affected dogs.…”

Selecting The Best Treatment Option For A Dog With Cushing’S Syndrome

“…The structure of the adrenal may be more important than its size. In hyperplastic adrenal glands the normal shape is preserved and the sonographic appearance is homogeneous [25]. Contrast-enhanced ultrasonography is a relatively new approach in evaluating adrenal glands [26][27][28].…”