Resumen de Clinical findings in dogs with incidental adrenal gland lesions determined by ultrasonography: 151 cases (2007–2010)
Objective—To determine the prevalence of and clinical features associated with incidental adrenal gland lesions (IAGLs) discovered during abdominal ultrasonography in dogs.
Design—Retrospective case series.
Animals—151 dogs with an IAGL and 400 control dogs.
Procedures—Reports of ultrasonographic examinations of the abdomen of dogs performed during a 3.5-year period were reviewed. Adrenal glands were classified as having an IAGL if a nodule or mass was described or the width of either gland was ≥ 10 mm. For dogs with an IAGL, information regarding signalment, concurrent disorders, and outcome was obtained from the medical record. Findings were compared with those in a control population of 400 dogs examined during the same period.
Results—An IAGL was detected in 151 of 3,748 (4%) dogs. Dogs with an IAGL were significantly older (median age, 11.25 years) and heavier (median body weight, 21 kg [46.2 lb]) than the control population (median age, 9.5 years; median body weight, 14 kg [30.8 lb]). Malignant tumors were reported in 6 of 20 (30%) dogs that underwent adrenal glandectomy or necropsy and had a maximum IAGL dimension that ranged from 20 to 46 mm; benign lesions all had a maximum dimension < 20 mm. Various coincidental conditions were reported in dogs with an IAGL, including nonadrenal gland malignant neoplasia in 43 (28.5%) dogs.
Conclusions and Clinical Relevance—IAGLs were more likely in dogs ≥ 9 years of age. On the basis of this small data set, malignancy should be suspected for IAGLs ≥ 20 mm in maximum dimension.
The use of advanced imaging modalities (eg, ultrasonography, CT, and MRI) in human patients has led to the routine identification of incidental adrenal gland masses. These are defined as a focal enlargement of the adrenal gland in patients without prior evidence of adrenal gland disease. Lesions found in patients undergoing imaging procedures as part of the staging process for cancer are inconsistently excluded from this definition in the human medical literature.1–3 The prevalence of such masses in humans is low, affecting only 2% to 5% of patients undergoing CT, but does increase with age.1–3 Most IAGLs in human patients without concurrent malignancy are benign and nonfunctional.3 Size of the mass is not a specific indicator of malignancy in human patients, although larger lesions are more likely to be a cortical carcinoma.1,4–6 Imaging characteristics, such as noncontrast CT attenuation, appear to be more useful predictors of malignancy, with low attenuation (ie, < 10 Hounsfield units) supporting a diagnosis of adenoma or hyperplasia in humans with cortical lesions.6,7 The first descriptions of the ultrasonographic appearance of normal canine adrenal glands were published in the mid-1990s.8,9 Prior to this time, the available technology did not support the routine identification of adrenal glands in healthy dogs.10,11 Since those first reports, the ability of an experienced sonographer to visualize the adrenal glands has continued to improve, and the identification, description, and measurement of both adrenal glands is now considered a standard part of an abdominal ultrasonographic examination in dogs. Therefore, IAGLs are now routinely detected in dogs, and veterinarians are faced with the challenge of defining the importance of these lesions.12–14 Advanced imaging modalities, such as CT, MRI, and positron emission tomography, may provide useful additional information but require anesthesia and incur substantial additional costs.15,16 Focal adrenal gland lesions (nodules and masses) or nonspecific enlargement may reflect one of many processes. A lesion may be a benign tumor (ie, a cortical adenoma) or a malignant tumor (ie, a cortical carcinoma, pheochromocytoma, or metastases). Alternatively, it may be a granuloma, cyst, or area of hyperplasia. Although evidence of vascular invasion indicates malignancy and is often associated with cortical carcinomas and pheochromocytomas, limited information is gained regarding biological behavior from ultrasonography alone.12,17,18 The goals of the study reported here were to determine the prevalence of IAGLs in dogs undergoing routine diagnostic abdominal ultrasonography at a veterinary teaching hospital, to describe the demographics of dogs with IAGLs and compare these findings with those in a control population, and to determine the diagnoses and outcome (where available) for dogs with an IAGL.
