Demographics, Imaging Findings, Diagnosis, and Outcome for 74 dogs Undergoing Adrenalectomy for an Incidental Mass.

Abstract

Background: Incidental adrenal masses (In-AMs) are routinely identified in dogs undergoing abdominal imaging. However, there is little information regarding likelihood of malignancy, and the risks versus benefits of surgical intervention.

Objectives: To compare findings in dogs with In-AMs against those with clinical adrenal masses (Cl-AMs); To identify pre-operative indicators of histologic diagnosis for dogs with In-AMs. Animals: 255 dogs undergoing laparoscopic adrenalectomy.

Methods: Demographics, lesion size, and histologic findings were compared for dogs with incidental versus clinical masses. Survival to discharge was determined for dogs with In-AMs.

Results: Masses were apparently incidental in 74/255 dogs (29.0%). Ages and body weights were similar to those with Cl-AMs (126.6 ±25.7 v 122.0 ±27.3 months [p=0.234], and 15 (3.1-96) v 11 (3.0-65) kg [p=0.178], respectively). Malignancy rates were similar (56.7% v 62.2% [p=0.463]), although In-AMs were more likely to be pheochromocytomas (34.3% v 12.2%; OR 3.76 [1.933—7.42]; p=0.0002). Maximal mass dimension (MMD) was similar for both groups (2.5 [0.9-14] v 2.5 [1.3-6.7] cm; p=0.832). Twenty In-AMs had MMD ≤2 cm, 8 of which were noted to have vascular invasion on imaging. However, 6/11 small, non-invasive In-AMs were malignant (3 pheochromocytomas, 3 carcinomas). Three dogs died from surgical complications.

Conclusion: These findings suggest that the majority of In-AMs are malignant, and that size is not predictive of histopathologic findings. Short-term outcomes following elective laparoscopic adrenalectomy are generally good. Previous recommendations to simply monitor non-invasive In-AMs with MMD ≤2 cm should be reconsidered.