🐶 New CT Insights: Do Lung Window Settings Really Improve Detection of Nasal Foreign Bodies in Dogs?

Comparative Diagnostic Value of Computed Tomography Lung and Bone Window Settings for the Detection of Nasal Foreign Bodies in 47 Dogs Presented to Two UK Referral Hospitals (2015–2023)

Nicoletta Fantaconi, Andrew T. Parry, Jose Labrador, Luis Alejandro Pérez López, Petra Agthe

Background

Nasal foreign bodies (FBs) are a common but challenging cause of canine nasal disease, often producing nonspecific signs such as sneezing, nasal discharge, and epistaxis. Computed tomography (CT) combined with rhinoscopy is the diagnostic gold standard, but plant material and other soft-tissue FBs may be difficult to visualize due to low attenuation or masking by secretions. In human medicine, lung window (LW) settings have been used to enhance detection of hypoattenuating FBs. This study aimed to compare the diagnostic performance of CT bone window (BW) and LW settings for identifying nasal FBs in dogs and to assess interobserver agreement.

Methods

This retrospective multicentre observational study included 47 dogs from two UK referral hospitals (2015–2023) with rhinoscopically confirmed nasal FBs. Pre-contrast CT scans of the head were independently reviewed in BW (window level 300 HU, width 1500 HU) and LW (level −500 HU, width 1400 HU) by two board-certified veterinary radiologists blinded to final diagnoses. Each review determined the presence or suspicion of FBs, with interobserver agreement assessed using Cohen’s kappa and intraclass correlation coefficients.

Results

Of 184 dogs reviewed, 47 met inclusion criteria. Most FBs were grass awns (64%), followed by grass blades (17%) and other plant or inorganic materials. The median age was 5 years, and common breeds included Cavalier King Charles Spaniels and West Highland White Terriers.

-FBs were confidently detected in 20% of BW assessments and 21% of LW assessments.

-Interobserver agreement was moderate (κ = 0.53 for BW; κ = 0.49 for LW).

-Most FBs were elongated, homogeneous, and located in the rostral or mid-nasal cavity.

-LW detected one additional FB not visible in BW, indicating marginal benefit in select cases.

-FBs were more frequently identified in acute than chronic presentations, likely due to less obstruction from mucosal secretions.

Limitations

Study limitations included small sample size, potential type II error, retrospective design, and reviewer blinding without consensus interpretation. Reviewers were allowed to adjust window parameters, introducing variability but replicating real-world practice. Chronic cases may have reduced visibility of FBs due to secondary nasal changes.

Conclusions

The study found no significant diagnostic advantage of the lung window over the bone window for detecting nasal FBs in dogs. However, switching between BW and LW settings may occasionally aid identification of subtle hypoattenuating materials, particularly plant fragments not surrounded by secretion. Routine CT review using both window types remains advisable for comprehensive assessment.

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