Silent Risk: Nearly 40% of Dogs Show Aspiration Without Cough on Swallow Studies

Incidence, Clinical Signs, and Videofluoroscopic Swallow Study Abnormalities Associated with Airway Penetration and Aspiration in 100 Dogs

Megan Grobman, Enrico Carluen, Carol R. Reinero

Background:
Airway penetration and aspiration (P-A) are known contributors to respiratory disease in humans and dogs. Videofluoroscopic swallow studies (VFSS), coupled with P-A scoring systems, are the gold standard in human medicine for evaluating airway protection during swallowing, but their use and associated findings in dogs are less characterized. This study aimed to determine the incidence of P-A, assess clinical signs associated with P-A, and identify dysphagic abnormalities that predispose to P-A in dogs.

Methods:
A retrospective analysis was performed on VFSS data and medical records from 100 client-owned dogs evaluated at two veterinary hospitals. Dogs were scored using a 7-point P-A scale; scores ≥3 were considered pathologic. VFSS findings were categorized into oral-preparatory, pharyngeal, and esophageal phase abnormalities. Additional diagnostics, including thoracic radiographs, respiratory fluoroscopy, and BALF analysis, were included where available. Statistical comparisons assessed associations between clinical variables, imaging findings, and P-A scores.

Results:
Pathologic P-A was identified in 39% of dogs. Notably, 36% of these had no respiratory clinical signs (occult P-A), and 28% had normal thoracic radiographs. Pharyngeal weakness and esophago-oropharyngeal reflux (EOR) were significantly associated with P-A and were identified as independent predictors. Pathologic P-A occurred across all swallowing phases but was most strongly linked to pharyngeal (87%) and esophageal (51%) dysfunction. No single clinical sign or demographic factor reliably distinguished dogs with P-A. Many cases of aspiration occurred without a protective cough response, raising concern for underdiagnosis without VFSS.

Limitations:
The retrospective design and lack of a healthy control group limit the ability to determine baseline P-A incidence. Diagnostic testing was not standardized across all cases, and the study could not assess the progression or resolution of P-A over time. The sample size limited statistical power for less common findings.

Conclusions:
VFSS revealed a high incidence of occult pathologic P-A in dogs, which cannot be reliably predicted by clinical signs or radiographs alone. Pharyngeal weakness and EOR are key risk factors. Given that many affected dogs showed no overt respiratory signs, VFSS should be considered essential for evaluating dysphagia and suspected aspiration in dogs to facilitate early intervention and prevent progression of aspiration-related respiratory disease.

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