CT can identify characteristic features of hypaxial muscle abscesses in dogs due to presumed migrating vegetal foreign material as well as additional changes along the migratory tract in other anatomic regions.

Hypaxial muscle abscess is an important differential in dogs presenting for abdominal or back pain, lameness, and nonspecific signs like fever, lethargy, and hyporexia. It can occur concurrently with intrathoracic disease such as pyothorax secondary to migrating vegetal foreign material. Twelve dogs that underwent CT of the lumbar spine or abdomen and had a diagnosed hypaxial abscess on surgical and/or microbiological examination were included in this retrospective, descriptive case series. Computed tomography findings and findings from other imaging modalities employed were described. Eleven dogs were hunting breeds. Clinical signs included lethargy, fever, increased respiratory effort, and abdominal or back pain. Radiography and/or ultrasonography were employed during preliminary work up at clinician discretion and respectively revealed changes consistent with osteomyelitis in the cranial lumbar vertebrae and heterogenous, hypoechoic areas in the hypaxial musculature consistent with abscesses. Computed tomography findings included enlargement of hypaxial muscles with well-defined fluid attenuating noncontrast enhancing areas with a contrast-enhancing rim consistent with abscesses, periosteal reaction and lysis of vertebrae, and retroperitoneal effusion. Four of the 12 cases in this series had material identified and removed at surgery. The other eight cases were presumed to be the same disease process based on compatible signalment, imaging findings, and microbiological results. Migrating vegetal foreign bodies are a common problem at the authors' institution. Computed tomography provided expedient, thorough visualization of the relevant hypaxial lesions for diagnostic and surgical planning purposes and also characterized intrathoracic components of this disease.
(© 2022 American College of Veterinary Radiology.)