Macroscopic and ultrasonographic anatomy of the brachial plexus in the American kestrel (Falco sparverius)

The American kestrel (Falco sparverius) is a small raptor frequently admitted to wildlife rehabilitation centers, often due to traumatic injuries requiring surgical intervention. Regional anesthesia techniques, particularly brachial plexus blocks, may improve perioperative management; however, species-specific anatomical and ultrasonographic data remain limited. This study aimed to characterize the macroscopic and ultrasonographic anatomy of the brachial plexus in F. sparverius and to assess the distribution of injectate following ultrasound-guided administration. Nineteen kestrels were allocated into three groups: anatomical dissection (n = 6), ultrasonographic evaluation (n = 8), and cadaveric ultrasound-guided dye injection 0.5 mL kg⁻¹ of a lidocaine-methylene blue solution resulted in consistent dye distribution within the plexus location (n = 5). The brachial plexus was formed by the ventral rami of spinal nerves C13-T2, organized into dorsal and ventral fascicles. Ultrasonographically, the brachial plexus appeared as small hypoechoic structures beneath the superficial and deep pectoral muscles using a ventral approach. These findings demonstrate that the brachial plexus of F. sparverius follows a typical avian pattern with species-specific variations and that the ventral ultrasonographic approach allows reliable visualization and accurate injectate delivery. This study provides anatomical and imaging data to support the development of regional anesthesia techniques in small raptors.