Comparison of imaging techniques to detect migrating foreign bodies. Relevance of preoperative and intraoperative ultrasonography for diagnosis and surgical removal.

Objective: To report the relative sensitivity of different diagnostic imaging (DI) techniques to detect migrating foreign bodies (FB) in subcutaneous and underlying soft tissue structures of dogs and evaluate the value of intraoperative ultrasonography (intraop-US).

Study Design: Retrospective study.

Sample Population: Forty-one dogs.

Methods: Medical records (2007-2019) of dogs that underwent surgery for a chronic abscess or draining tract were included when preoperative US (preop-US), computed tomography (preop-CT), or preop-MRI, and at least 6 months of follow-up information were available. Collected data included the DI techniques used, DI findings, and surgical findings. The relative sensitivity of each preoperative DI (preop-DI) technique was calculated. Dogs were divided into two groups, dogs that underwent only a preop-DI examination (group A) and dogs that underwent an additional intraop-US (group B). The success rates for FB surgical removal were compared between groups.

Results: The relative sensitivity of preop-US and preop-CT/MRI was 88% (95% CI, 70%-95.8%) and 57.1% (95% CI, 32.6%-78.6%), respectively. The success rate for FB removal was higher in group B (89.5%) than in group A (59.1%; P = .038). Clinical resolution occurred in 90.2% of dogs for a median duration of follow-up of 4.2 years (6 months to 9.3 years).

Conclusion: Preoperative US seems more suitable than preop-CT/MRI for detection of migrating FB in subcutaneous and underlying soft tissue structures. The use of intraop-US increases the success rate for FB surgical removal.

Clinical Significance: Intraoperative US should be used in combination with preop-US to increase the likelihood of migrating FB surgical removal in dogs.