Ultrasonographic findings may be useful for differentiating interdigital abscesses secondary to migrating grass awns and interdigital furunculosis in dogs

Abstract

Grass awn migration and furunculosis are common diseases in dogs that can lead to interdigital subcutaneous lesions with a similar clinical presentation, and occasionally similar ultrasonographic images, but different treatments are required. This retrospective, multicentric, analytical study aimed to determine whether epidemiological, clinical, and ultrasonographic features could be used to differentiate interdigital furunculosis and abscesses secondary to migrating grass awns. Fifty-nine dogs that underwent interdigital ultrasonography were included (interdigital furunculosis [IDF], n = 27; interdigital abscess secondary to a migrating grass awn [IAGA], n = 32). Ultrasonographic images were reviewed by two observers blinded to the diagnosis, who graded nine qualitative and four quantitative parameters for each patient. In both groups, pruritus/licking (IDF 74%, IAGA 70%), a discharging interdigital wound (63% for each group), and thoracic limb involvement (IDF 88%, IAGA 75%) were common features. On ultrasound, a subcutaneous multilinear hyperechoic main element was identified in most dogs (IDF 85%, IAGA 100%). The ability to display this element in a single plane (P < 0.01), the absence of additional hyperechoic linear elements in different planes (P < 0.01), and a surrounding hypoechoic halo (P < 0.05) were significantly more common in dogs with interdigital abscesses secondary to migrating grass awns. A cut-off value of 0.83 cm for the length of the main multilinear element provided a sensitivity of 91% and a specificity of 87% in the diagnosis of a migrating grass awn. Findings supported prioritizing a differential diagnosis of interdigital abscesses secondary to grass awns in dogs with these ultrasonographic characteristics.

Keywords: dog; grass awn; interdigital furunculosis; ultrasound.