Do we need a different cut-off for Frenchy normal trachea size?

January 19, 2025

Marina du Preez, Ryan Taggart, Nima Nakahara, Jonothan Tuke, Jia Wen Siow

Background
Tracheal hypoplasia, a congenital condition characterized by a narrowed tracheal lumen, is often associated with brachycephalic obstructive airway syndrome (BOAS). Diagnostic measurements for tracheal hypoplasia have primarily been based on English bulldogs or generalized “bulldog” data, with no breed-specific standards for French bulldogs. This study aimed to evaluate tracheal diameter ratios (TD:Ti and TD:ML) in French bulldogs to establish breed-specific cut-off values and better characterize the condition in this breed.

Methods
A retrospective observational study analyzed 139 French bulldogs from two Australian veterinary hospitals. Right lateral thoracic radiographs were used to measure tracheal diameter to thoracic inlet (TD:Ti) and tracheal diameter to manubrium length (TD:ML) ratios. Cases with pulmonary or cardiovascular diseases were segregated, and statistical analyses assessed interobserver reliability, anatomical variations, and potential covariates affecting measurements.

Results
-Tracheal Ratios:
-Mean TD:Ti for healthy French bulldogs was 0.15 (±0.02).
-Mean TD:ML was 0.32 (±0.07) for dogs with normal manubriums.

-Observer Agreement: High interobserver correlation for TD:ML (ICCinter = 0.9562) and good for TD:Ti (ICCinter = 0.8739).

-Anatomical Variations:
-Thoracic hemivertebrae were observed in 94.2% of dogs.
-Sternal malformations occurred in 30.2%.

-Sex Differences: Female dogs had a significantly lower mean TD:Ti than males (p = 0.0225). However, females were not overrepresented in the group below the cut-off value (0.15 ± 0.02).

-Pulmonary Disease: No statistically significant effect of pulmonary disease on tracheal ratios (p = 0.8134).

Limitations
The study's retrospective design and inclusion of hospitalized patients may limit generalizability. Measurements were affected by variable radiographic positioning and other anatomical anomalies common in French bulldogs. The weak correlation between TD:Ti and TD:ML highlights the need for further validation of these methods.

Conclusions
This study establishes baseline tracheal diameter ratios for French bulldogs, with a proposed TD:Ti cut-off of 0.15 for tracheal hypoplasia. The TD:ML method demonstrated excellent interobserver reliability and may serve as a promising alternative diagnostic metric. Further studies are required to refine these methods and explore their clinical implications across broader populations.

Common measurements used for diagnosing tracheal hypoplasia from digital radiographs. The figure depicts a right lateral thoracic digital radiograph of a French bulldog with included measurements commonly used when diagnosing tracheal hypoplasia. (A) Thoracic inlet distance (Ti) = 6.11 cm. (B) Tracheal lumen diameter (TD) = 9.21 mm. (C) Third rib width (3R) = 4.36 mm. (D) Manubrium length (ML) = 2.75 cm. White arrows, thoracic vertebral anomalies. Black arrow, semi-fused manubrium.

How did we do?

Login or Subscribe to participate in polls.

Disclaimer: The summary generated in this email was created by an AI large language model. Therefore errors may occur. Reading the article is the best way to understand the scholarly work. The figure presented here remains the property of the publisher or author and subject to the applicable copyright agreement. It is reproduced here as an educational work. If you have any questions or concerns about the work presented here, reply to this email.