P Thong 1, B Hopper 1, G Tenni 2, Z Lenard 1
Background
Canine spirocercosis, caused by the nematode Spirocerca lupi, can lead to severe and often fatal thoracic disease in dogs, but has been rarely reported in Australia. Radiographic features of this condition are well-documented in endemic regions but less so in newly recognized areas. This study aimed to describe the thoracic radiographic findings associated with confirmed spirocercosis in Australian dogs to improve early recognition and diagnosis.
Methods
This retrospective case series analyzed thoracic radiographs from 13 client-owned dogs in Australia with confirmed spirocercosis, either via endoscopy, histopathology, or post-mortem examination. Radiographs were evaluated for presence and features of esophageal masses, aortic changes, pulmonary lesions, and other thoracic abnormalities by board-certified radiologists. Additional clinical and diagnostic data were reviewed to correlate radiographic findings with disease progression.
Results
The most consistent radiographic feature was a soft tissue mass in the caudal esophagus, present in 11 of 13 dogs. Other frequent findings included spondylitis of thoracic vertebrae (8 dogs), and aortic mineralization or dilation (7 dogs). Pulmonary nodules, suggestive of metastasis, were observed in 4 cases. Mediastinal widening and pleural effusion were less common. Most masses were associated with smooth or lobulated contours, and some demonstrated gas lucencies. Aortic involvement often manifested as undulating or tortuous contours. These findings aligned with chronic parasitic migration and inflammation typical of S. lupi infection.
Limitations
The study was limited by its retrospective design, small sample size, and inherent selection bias due to reliance on confirmed cases. Not all dogs had complete imaging or advanced diagnostics, which may have led to underreporting of certain features. Additionally, the absence of a control group limits generalizability of findings.
Conclusions
Thoracic radiography remains a valuable diagnostic tool for canine spirocercosis in Australia, particularly when characteristic caudal esophageal masses and aortic changes are present. Awareness of these imaging findings can facilitate earlier suspicion and diagnosis of this emerging disease in non-endemic regions.
Unsedated (A) and post-gastro-oesophageal endoscopy anaesthetised (B) right lateral projections of the thorax; endoscopic image of oesophageal nodule (C) in the same patient. In (A), there is an ill-defined soft tissue opacity structure in the caudodorsal mediastinum (‘X’) that was confirmed to be the caudal oesophageal nodule. Note the ventral faintly mineralised spondylitis from T6-11 (asterisks on image A) visible on both projections. Better visualised in (B), the aortic arch has mild focal bulging past the cranial margins of the cardiac silhouette (white arrows). Image (C) shows the classic broad-based oesophageal nodule with the operculum (black arrow) through which the female worm will deposit eggs into the lumen.20 Radiographs and photo credit: Mount Isa Veterinary Surgery.
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