Imaging the Invisible: Radiographic and CT Clues to Canine Parasitic Diseases

A Review of Radiographic and Computed Tomographic Features of Helminth and Arthropod Parasitic Diseases in Dogs

Alice Birckhead; Richard Malik; Shokoofeh Shamsi; David Jenkins; Ann Carstens

Background

Parasitic diseases are an important yet frequently underdiagnosed cause of morbidity in dogs, with some posing zoonotic risks and others expanding their geographic range due to climate change, animal movement, and ecological factors. Clinical signs are often nonspecific, contributing to misdiagnosis or delayed recognition. Although diagnostic imaging can reveal parasites or parasite-associated pathology, radiographic and CT features of many parasitic diseases have not been comprehensively summarized. This review aimed to collate and synthesize published radiographic and computed tomographic findings of helminth and arthropod parasitic diseases in dogs.

Methods

A comprehensive literature search was conducted using PubMed, Web of Science, and Google Scholar up to January 10, 2025. Searches targeted radiographic and CT descriptions of canine parasitic diseases, drawing from veterinary parasitology textbooks, CAPC and ESCCAP guidelines, and peer-reviewed English-language publications. Eighteen parasitic diseases were included based on the availability of imaging descriptions. Parasites were organized by the primary organ system affected, with each section summarizing parasite distribution, life cycle, clinical manifestations, and reported radiographic and CT features. The review incorporated 240 references, including case reports, case series, and experimental studies.

Results

Radiographic and CT findings varied widely among parasitic diseases and ranged from pathognomonic to nonspecific. Well-characterized imaging patterns were described for parasites such as Spirocerca lupi, Dirofilaria immitis, Angiostrongylus vasorum, and Paragonimus spp., including esophageal masses with spondylitis, cardiopulmonary arterial enlargement, peripheral alveolar–interstitial lung patterns, and pulmonary cystic or nodular lesions. For many other parasites, imaging findings were limited to isolated case reports and primarily reflected secondary pathology, such as granulomatous inflammation, hemorrhage, mineralization, or organ distortion. Direct visualization of parasites was uncommon; instead, imaging most often demonstrated multifocal lesions associated with parasite migration or host immune responses. CT provided improved detection of subtle changes and better lesion characterization compared with radiography in several diseases.

Limitations

The authors highlighted that much of the available literature consists of case reports or small case series, often lacking standardized imaging descriptions or histopathologic confirmation. Imaging findings were sometimes described by non-radiologists, leading to inconsistencies in terminology and detail. Potential confounding factors such as co-infections or concurrent disease were frequently not excluded. CT findings were particularly underreported for many parasitic diseases.

Conclusions

This review represents the first comprehensive synthesis of radiographic and CT features of helminth and arthropod parasitic diseases in dogs. While certain parasites exhibit characteristic imaging patterns, many produce nonspecific findings that can mimic other disease processes, including neoplasia. Diagnostic imaging is a valuable adjunct in the investigation of parasitic disease but must be interpreted alongside clinical, epidemiological, and laboratory data. The authors emphasize a substantial need for further research—particularly involving CT—to improve recognition and understanding of both well-known and emerging parasitic infections in dogs.

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