Assessment of computed tomography derived cricoid cartilage and tracheal dimensions to evaluate degree of cricoid narrowing in brachycephalic dogs

Evaluation of measurements for tracheal hypoplasia in French bulldogs

Tracheal narrowing may increase airflow resistance, resulting in clinical manifestations associated with brachycephalic obstructive airway syndrome (BOAS). When diagnosing tracheal hypoplasia, established values are based on measurements established for English bulldogs or non-specific "bulldog" breeds. The objective of this study was to investigate tracheal diameter ratios in French bulldogs to gain a better understanding of what would constitute tracheal hypoplasia in this breed. A retrospective observational analysis was conducted to measure the right lateral thoracic radiographs of 139 French bulldogs to investigate tracheal diameter ratios. Pulmonary disease was observed in 55/139 dogs. The mean TD:Ti for healthy French bulldogs was 0.15 (±0.02), and the mean TD:ML was 0.32 (±0.07). 44/84 dogs had a TD:Ti < 0.15 (±0.02), and 37/65 dogs had a TD:ML < 0.32 (±0.07). At least one thoracic vertebral anomaly was observed in 131/139 of evaluated French bulldogs, and sternal malformations were observed in 42/139 dogs. TD:ML showed an excellent interclass correlation between observers (ICCinter 0.9562). The listed covariables were compared for statistical significance when measuring relative tracheal ratios, and none were found. There was a statistically significant relationship between TD:Ti and sex. An objective value for tracheal hypoplasia in French bulldogs has previously not been established. The mean TD:Ti described for French bulldogs in this study is higher than that previously described in other "bulldog" populations. The mean TD:ML is similar to previously reported for non-brachycephalic and non-bulldog brachycephalic small breed dogs. The correlative relationship between TD:Ti and TD:ML was statistically significant but weak.

Awake 160-Slice Computed Tomography for Upper Airway Evaluation in 17 Dogs

This study investigated using a 160-slice multidetector computed tomography (CT) scanner for conscious image acquisition in dogs with upper airway disease, and describes findings in dogs that had previously undergone soft palate surgery. Seventeen client-owned dogs with upper airway disease were retrospectively reviewed, and classified into three groups: group I, "untreated brachycephalic obstructive airway syndrome (BOAS) patients"; group II, "previously treated BOAS patients"; and group III, "patients with respiratory disease other than BOAS". Data included signalment, clinical history, direct laryngoscopy and endoscopy findings, previous surgeries and CT findings. CT scans in group I revealed overlong and thickened soft palates in all dogs, and signs of laryngeal collapse in four dogs. Patients in group II exhibited normal soft palate lengths, while patients in group III displayed various findings such as nasopharyngeal narrowing and tracheal collapse. Upper airway examinations under general anaesthesia confirmed most CT findings. This study demonstrates the feasibility and value of conscious CT scanning for assessing upper airway diseases in dogs, providing valuable diagnostic information while eliminating the need for chemical immobilisation, thus reducing patient stress and cost. These findings offer new insight into upper airway anatomy in awake patients, especially in brachycephalic breeds, and lay a foundation for future research.

Computer tomography measurements of the airway and thoracic cavity do not provide support for bronchial conformation as a predisposing factor of left cranial lung lobe torsion in pugs

The objective of this retrospective clinical study was to determine if airway or thoracic cavity measurements in pugs, particularly the left cranial lung lobe, were significantly different from brachycephalic and mesocephalic control. Thoracic computed tomographic studies of 10 pugs, French bulldogs (FB), and Jack Russell Terriers (JRT) were analyzed. Thoracic height: width ratio (H:W), cross-sectional areas of the left mainstem bronchus (CSA LMB), left cranial lung lobe bronchus (CSA LCrBr), left caudal lung lobe bronchus (CSA LCauBr), CSA LCrBr relative to length (CSA LCrBr/length) and CSA LCauBr/length were measured and adjusted to body weight (/kg). CSA LMB/kg, CSA LCauBr/length/kg, and CSA LCrBr/length /kg were smaller in pugs and FB compared with JRT (P < .05), but no differences were found between pugs and FB. Cross-sectional areas of left cranial lung lobe bronchus /kg and CSA LCauBr/kg were smaller in pugs than JRT (P < .05), but no differences were found between pugs and FB or FB and JRT. No difference was found in thoracic H:W between any breeds. This demonstrated that pugs and FB had significantly narrower bronchi CSA/lengths ratios compared with JRT, but this was not limited to the LCBr. Airway measurements were not significantly different between brachycephalic breeds; therefore, the pugs' predisposition to left cranial lung lobe torsion cannot be solely explained by narrower lower airways.

Radiographic determination of the tracheal indices at caudal cervical, thoracic-inlet, and intra-thoracic trachea in non-bulldog brachycephalic breeds without evidence of cardiorespiratory disease

BACKGROUND

Congenital tracheal hypoplasia is a component of airway syndrome affecting a wide variety of brachycephalic dog breeds. Several radiographic procedures were utilized to assess vertical tracheal diameter (VTD) in dogs. The objective of this study was to calculate the tracheal indices at the caudal cervical, thoracic-inlet, and intra-thoracic tracheal regions on the right lateral thoracic radiograph to further establish a screening protocol for diagnosis of tracheal hypoplasia in non-bulldog brachycephalic breeds. Dogs without clinical or radiographic evidence of tracheal, respiratory, or cardiovascular abnormalities were investigated. The absolute and average VTDs were normalized by manubrium length (ML), thoracic-inlet distance (Ti-D), and proximal 3rd rib width (PR3-W). Manubrium-tracheal index (M-TI), thoracic inlet-tracheal index (Ti-TI), and proximal R3-tracheal score (PR3-TS) were calculated. Correlations between averaged VTD and each of the normalizing parameters (ML, Ti-D, and PR3-W), and between M-TI and each of the previously established procedures (Ti-TI and PR3-TS) were determined.

RESULTS

Eighty healthy subjects met the inclusion criteria for the study. There were significant differences (P ≤ 0.0001) among the means of absolute and normalized VTDs at the 3 tracheal levels. The smallest VTD was identified at the thoracic inlet. The average tracheal diameter showed a better correlation with ML (rs=0.81, P < 0.0001) compared to Ti-D and PR3-W. There was a strong correlation (rs=0.83, P < 0.0001) between the averaged M-TI and Ti-TI.

CONCLUSION

Radiographic M-TI could be an alternative to traditional procedures to assess the tracheal lumen in non-bulldog brachycephalic dogs. M-TI < 0.39, < 0.30, or < 0.34 at caudal cervical, thoracic inlet, or intrathoracic trachea, respectively, may indicate tracheal hypoplasia in non-bulldog brachycephalic breeds. Screening of tracheal diameter using M-TI should be recommended. However, further investigation of non-bulldog brachycephalic breeds with cardiac and/or respiratory disease is indicated.

Rostral nasopharyngeal CT measurements in Chihuahuas and Pomeranians are smaller than those measured in Dachshunds

Chihuahuas and Pomeranians are often afflicted with obstructive upper respiratory tract disease. Previous computed tomographic (CT) studies have described the dimensions and abnormalities of different parts of the upper respiratory tract in brachycephalic dogs. However, Chihuahuas and Pomeranians were not included. The objective of this study was to determine the transverse-sectional (TSA) dimensions of the nasopharynx, cricoid, and trachea of Chihuahuas and Pomeranians, and investigate whether or not Chihuahuas and Pomeranians had smaller airway dimensions than another non-brachycephalic breed (Dachshund). A retrospective, descriptive, single-center cross-sectional cohort study was performed. CT studies of 88 dogs were included (42 Chihuahuas, 29 Dachshunds, and 17 Pomeranians). The TSA of the rostral, mid, and caudal aspect of the nasopharynx, the cricoid and trachea at the level of C4 were determined. For all these locations, TSA/weight, nasopharynx/cricoid, nasopharynx/trachea, and cricoid/trachea ratios were determined. The rostral nasopharynx was the smallest part of the upper airways in Chihuahuas and Pomeranians. Chihuahuas had significantly smaller rostral nasopharynx TSA/weight ratios compared to Dachshunds (P < 0.0001). The rostral nasopharynx TSA/cricoid ratio and the rostral nasoharynx/trachea ratio for Chihuahuas were significantly smaller than both that of Pomeranians (P < 0.0001 and P = 0.00027) and Dachshunds (P < 0.0001 and P = 0.00084). Pomeranians had significantly smaller cricoid TSA/weight ratios compared to Chihuahuas (P = 0.0014) and Dachshunds (P = 0.00028). This study demonstrated that the nasopharynx is narrow in Chihuahuas and Pomeranians, with the smallest dimensions located at the rostral part of the nasopharynx.

Prevalence of bronchial wall thickening and collapse in brachycephalic dogs with and without brachycephalic obstructive airway syndrome and in nonbrachycephalic dogs

OBJECTIVE

To assess the prevalence of bronchial wall thickening (BWT) and collapse in brachycephalic dogs with and without brachycephalic obstructive airway syndrome (BOAS) and in nonbrachycephalic dogs.

ANIMALS

85 dogs with no history of lower respiratory tract disease that underwent CT of the thorax.

PROCEDURES

Electronical medical records for March 2011 through August 2019 were reviewed to identify brachycephalic dogs with BOAS (BOAS group) and brachycephalic dogs without BOAS (BDWB group) that did not have any evidence of lower respiratory tract disease and had undergone thoracic CT. A population of nonbrachycephalic dogs of similar weight (control dogs) was also retrospectively recruited.

RESULTS

BWT was identified in 28 of 30 (93.3%; 95% CI, 80.3% to 98.6%) dogs in the BOAS group, 15 of 26 (57.7%; 95% CI, 38.7% to 75.0%) dogs in the BDWB group, and 10 of 28 (35.7%; 95% CI, 20.1% to 54.2%) control dogs. On multivariable analysis, only brachycephalic conformation (P < 0.01) and body weight (P = 0.02) were significantly associated with the presence of BWT. Bronchial collapse was identified in 17 of 30 (56.7%; 95% CI, 39.0% to 73.1%) dogs in the BOAS group, 17 of 26 (65.4%; 95% CI, 46.3% to 81.3%) dogs in the BDWB group, and 3 of 28 (10.7%; 95% CI, 3.1% to 25.9%) control dogs. On multivariable analysis, only brachycephalic conformation was significantly (P < 0.01) associated with the presence of bronchial collapse.

CLINICAL RELEVANCE

A relationship between brachycephalic conformation and body weight with BWT was established, with heavier dogs having thicker bronchial walls. However, further studies are required to investigate the cause. Bronchial collapse was also more common in dogs with brachycephalic conformation, which is in agreement with the previously published literature.

Radiographic vertical tracheal diameter assessment at different levels along the trachea as an alternative method for the evaluation of the tracheal diameter in non-brachycephalic small breed dogs

Background

Tracheal narrowing due to congenital tracheal hypoplasia, acquired tracheal stenosis and tracheal collapse can lead to life-threatening respiratory distress. Tracheal hypoplasia has been identified in brachycephalic dog breeds, predominantly English Bulldogs, by measuring the tracheal diameter compared to the diameter of the thoracic inlet and creating a ratio. However, reference ranges for tracheal diameter have not been established for non-brachycephalic small breed dogs. It would be advantageous to have established tracheal diameters for non-brachycephalic small breed dogs, as these are the dogs most at risk of tracheal collapse. The main objective, of this study was to radiographically evaluate vertical tracheal diameter (VTD) at three standardized locations along the trachea of non-brachycephalic small breed dogs, in an attempt to further establish a screening diagnostic protocol for canine tracheal hypoplasia. Medical records and thoracic radiographs of non-brachycephalic small breed dogs without respiratory disease were reviewed. Right lateral radiographs were reviewed. The absolute and average VTDs at three locations (location A: caudal cervical VTD; location B thoracic inlet VTD; location C: intrathoracic VTD) were standardized by manubrium length (ML), as well as by the previously utilized thoracic inlet distance (Ti-D) and proximal 3rd rib width (PR3-W) to calculate manubrium-tracheal index (M-TI), thoracic inlet-tracheal index (Ti-TI), and proximal R3-tracheal score (PR3-TS), respectively. Correlations between averaged tracheal diameter and each of the ML, Ti-D, and PR3-W, and between M-TI and each of Ti-TI and PR3-TS were calculated.

Results

Eighty-one healthy dogs met the criteria for inclusion. Significant differences (P < 0.0001) were identified among the mean values of the absolute and standardized VTDs at levels A, B, and C. The smallest tracheal diameter was identified at the level of the thoracic inlet (Level B).

The average VTD correlated better with ML (r_s = 0.82, P < 0.0001) compared to Ti-D and PR3-W. A relatively strong correlation (r_s = 0.77, P < 0.0001) was identified between the averaged manubrium tracheal index (M-TI) and thoracic inlet tracheal index (Ti-TI).

Conclusion

M-TI is an appropriate alternative to Ti-TI and PR3-TS to radiographically evaluate VTD in dogs. M-TI < 0.43, < 0.34, or < 0.38 at level A, B, or C, respectively, may indicate tracheal hypoplasia in non-brachycephalic small breed dogs. Screening of canine VTD could be achieved using M-TI.

Abnormal hyoid conformation in French Bulldogs: case report and computed tomographic anatomical comparison

BACKGROUND

Brachycephalic obstructive airway syndrome (BOAS) is common in brachycephalic breeds and comprises multiple anatomic characteristics. Computed tomography (CT) is increasingly used in the preoperative assessment of dogs presenting with BOAS. We describe the case of a French Bulldog with a presumed congenital hyoid malformation and anatomic comparison of hyoid morphology between French Bulldogs and mesaticephalic dogs using CT.

METHODS

Skull CT studies of French Bulldogs and mesaticephalic dogs presenting to two referral hospitals between 2013 and 2020 were collected. The degree of curvature of the basihyoid bone and the relative ventrodorsal thickness (RVD) were determined using a novel measurement technique. A circle of best fit was applied to the inside arc of the basihyoid bone, and the radius and sector angle within the basihyoid bone were recorded. The RVD was defined by the ventrodorsal thickness divided by the width in the frontal plane.

RESULTS

The basihyoid bone of French Bulldogs had a greater mean ± SD RVD of 0.23 ± 0.04 compared to 0.16 ± 0.03 in mesaticephalic dogs (P < 0.01). The sector angle was also greater in French Bulldogs, measuring 144.08 ± 20.88° compared to 103.94 ± 16.49° in mesaticephalic dogs (P < 0.01).

CONCLUSION

This case of hyoid malformation in a French Bulldog reports a rarely documented condition that complicated the management of BOAS. Comparative assessment of hyoid conformation revealed more acute curvature and greater RVD in French Bulldogs than in mesaticephalic dogs. This may represent an additional distorted anatomic component of brachycephalic skull morphology.

Influence of computed tomographic dimensions of the nasopharynx on middle ear effusion and inflammation in pugs and French bulldogs with brachycephalic airway syndrome

OBJECTIVE

To compare the prevalence of middle ear abnormalities in pugs and in French bulldogs and evaluate the influence of nasopharyngeal dimensions on middle ear effusion.

STUDY DESIGN

Retrospective study.

ANIMALS

Thirty pugs and 30 French bulldogs with brachycephalic airway syndrome and no known history of ear disease.

METHODS

Computed tomographic (CT) studies were reviewed for middle ear effusion, mucosal contrast enhancement, signs of osteitis, and tympanic wall thickness. Soft palate thickness and cross-sectional areas of the nasopharynx at the opening of the auditory tube were measured and normalized to each individual's skull index before statistical comparison between breeds. Statistical dependence of middle ear abnormalities and nasopharyngeal dimensions was assessed by using Spearman's rank correlation tests.

RESULTS

Middle ear effusion was observed in 17 of 30 (56.7%) French bulldogs and five of 30 (16.7%) pugs. Contrast enhancement of the tympanic bulla was noted in 25 of 60 (41.6%) French bulldog ears and three of 60 (5.0%) pug ears. The cross-sectional airway dimensions (difference [Δ] = 0.31 cm² , P < .0001) and soft palate thickness (Δ = 0.44 cm, P < .0001) were reduced in pugs compared with in French bulldogs. Weak correlations were detected between soft palate thickness and nasopharyngeal dimensions and presence of tympanic bulla effusion (r = 0.324 and r = 0.198, respectively) or contrast enhancement (r = 0.270 and r = 0.199, respectively).

CONCLUSION

Middle ear effusion and inflammation were more common in French bulldogs than in pugs and did not seem related to nasopharyngeal dimensions.

CLINICAL SIGNIFICANCE

French bulldogs with brachycephalic airway syndrome seem predisposed to middle ear effusion and inflammation.

Unrecognized difficult airway management during anesthesia in two brachycephalic dogs with narrow cricoid cartilage

Difficulty in airway management during anesthesia was noted in a 10-year-old, castrated, male Pekingese dog and a 13-year-old male French Bulldog. They showed strong resistance during tracheal tube insertion through the subglottic lumen. Therefore, the airway was secured by using a small endotracheal tube or supraglottic airway device. Computed tomography scan revealed a markedly narrower vertical dimension of the cricoid cartilage compared to that seen in common brachycephalic breeds. Posterior glottis was relatively more accessible for translaryngeal intubation in the present cases. Our findings showed that brachycephalic airway syndrome may be associated with narrow cricoid cartilage. To the best of our knowledge, this is the first clinical case report of airway management during anesthesia in dogs with narrow cricoid cartilage.

Ultrasonographic measurement of the adrenal gland in neonatal foals: reliability of the technique and assessment of variation in healthy foals during the first five days of life

BACKGROUND

Adrenal gland ultrasonographic measurements are useful in clinical evaluation of patients with adrenal dysfunction in several species. In human healthy neonates, the ultrasonographic size of the adrenal glands decreases during the first days of life. Ultrasonography of adrenal glands was demonstrated to be feasible in neonatal foals. The aims of this study were to describe a technique for ultrasonographic measurement of adrenal gland size to test its reliability in neonatal foals, and to assess any variation of ultrasonographic measurements during the first five days of life in healthy foals.

METHODS

First, measurements of the adrenal glands were retrospectively obtained by three observers in 26 adrenal gland images of 13 healthy and sick neonatal foals. The interobserver and intraobserver agreement were tested. Later, adrenal gland ultrasonographic images and measurements were acquired by one operator in 11 healthy neonatal foals at one, three and five days of life and differences among the measurements obtained at the different time points were assessed.

RESULTS

Interobserver agreement ranged from fair to excellent (0.48-0.92), except for cortex width (<0.4); intraobserver agreement ranged from good to excellent (0.52-0.98). No significant differences were found among the measurements obtained at one, three and five days of life.

CONCLUSION

Adrenal glands ultrasonographic measurements can be obtained consistently in equine neonates, and in contrast to people they do not vary during the first five days of life in healthy foals.

Histological and mechanical comparisons of arytenoid cartilage between 4 brachycephalic and 8 non-brachycephalic dogs: A pilot study

Brachycephalic airway syndrome (BAS) is a well-established cause of respiratory distress in dogs. BAS without surgical correction results in eventual laryngeal collapse. Arytenoid lateralization has been used to treat severe laryngeal collapse with some highly variable results. Chondromalacia and decreased stiffness of the arytenoid cartilage has been postulated a source of failure after arytenoid lateralization but no report of the histological characteristics and mechanical strength of arytenoid cartilage in brachycephalic dogs has been reported. Here we report histological and mechanical features in arytenoid cartilage of brachycephalic dogs. We identified the arytenoid cartilage in brachycephalic dogs presented degenerative histological characteristics and decreased load to failure and stiffness compared to that in non-brachycephalic dogs. Together, these observations suggest that degenerative condition of arytenoid cartilage in brachycephalic dogs could contribute to chondromalacia and mechanical weakness of arytenoid cartilage and result in cause of failure after arytenoid lateralization.

Prognostic indicators of short-term outcome in dogs undergoing surgery for brachycephalic obstructive airway syndrome

BACKGROUND

The aims of this study were to assess the impact of epidemiological variables, severity of presurgical respiratory signs, diagnostic findings from pharyngeal and laryngeal examination using a new grading scheme and CT scan images, on postsurgical outcome in dogs undergoing surgery for brachycephalic obstruction airway syndrome (BOAS).

METHODS

An owner-based questionnaire was used to grade dogs based on their respiratory signs before surgery and at least six weeks after surgery. Epidemiological data and results from presurgical pharyngeal and laryngeal examination and CT scan findings for 75 dogs undergoing airway surgery were collected from the medical records.

RESULTS

70.7 per cent of dogs showed an improvement in respiratory signs following rhinoplasty and palatoplasty. This improvement was associated with the severity of inspiratory efforts and the Poncet score on presentation, but not with any other clinical sign or anatomical abnormality found during BOAS assessment, nor by the degree of craniofacial shortening as determined by CT-scan. Presurgical snoring was positively associated with the degree of narrowing of pharyngeal dimensions.

CONCLUSIONS

Dogs presenting with clinical signs of BOAS benefit from rhinoplasty and palatoplasty alone. The degree of narrowing of pharyngeal dimensions appears to be associated with severity of snoring while soft palate length alone was not.