Comparison of Radiography and Computed Tomography for Determining Tracheal Diameter and Length in Dogs

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.

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.

Cadaveric evaluation of fluoroscopy-assisted placement of one-lung ventilation devices for video-assisted thoracoscopic surgery in dogs

OBJECTIVE

To evaluate the feasibility of fluoroscopy-assisted placement of one-lung ventilation (OLV) devices in dogs.

STUDY DESIGN

Experimental study.

SAMPLE POPULATION

Canine cadavers (n = 8) weighing between 20.2 and 37.4 kg.

METHODS

Thoracoscopic access with a two-port approach was established to evaluate bilateral lung ventilation patterns. Advancement of a left-sided Robertshaw double-lumen endobronchial tube (DLT) and the EZ-blocker (EZ) were evaluated under direct fluoroscopic guidance. Each dog also underwent bronchoscopy-assisted placement of an Arndt endobronchial blocker (EBB). Time to initial placement, success of creating complete OLV (after initial placement attempt and after up to two repositionings), and ease of placement score were recorded. Device position was evaluated bronchoscopically after each fluoroscopy-assisted placement attempt.

RESULTS

Time to initial placement was significantly shorter for EZ than for DLT and EBB. The rate of successful placement after up to two repositioning attempts was 87.5%, 87.5%, and 100.0% on the right and 87.5%, 100.0%, 100.0% on the left for DLT, EZ, and EBB, respectively, and was not different between devices. Ease of placement scores were significantly higher for DLT compared with EZ and EBB on both the left and the right sides.

CONCLUSION

Fluoroscopy-assisted placement of DLT and EZ appears feasible in canine cadavers. EZ-blocker placement was efficient and technically easier than DLT, but positioning must be adapted for dogs. Bronchoscopy-assisted placement of EBB remains highly successful.

CLINICAL SIGNIFICANCE

Fluoroscopy-assisted placement of EZ and DLT is a useful alternative to bronchoscopy-assisted placement of these OLV devices.

Immediate, short-, and long-term changes in tracheal stent diameter, length, and positioning after placement in dogs with tracheal collapse syndrome

BACKGROUND

Intraluminal tracheal stenting is a minimally invasive procedure shown to have variable degrees of success in managing clinical signs associated with tracheal collapse syndrome (CTCS) in dogs.

OBJECTIVES

Identify immediate post-stent changes in tracheal diameter, determine the extent of stent migration, and stent shortening after stent placement in the immediate-, short-, and long-term periods, and evaluate inter-observer reliability of radiographic measurements.

ANIMALS

Fifty client-owned dogs.

METHODS

Retrospective study in which medical records were reviewed in dogs with CTCS treated with an intraluminal tracheal stent. Data collected included signalment, location, and type of collapse, stent diameter and length, and post-stent placement radiographic follow-up times. Radiographs were used to obtain pre-stent tracheal measurements and post-stent placement measurements.

RESULTS

Immediate mean percentage change was 5.14%, 5.49%, and 21.64% for cervical, thoracic inlet, and intra-thoracic tracheal diameters, respectively. Ultimate mean follow-up time was 446 days, with mean percentage change of 2.55%, 15.09%, and 8.65% for cervical, thoracic inlet, and intra-thoracic tracheal diameters, respectively. Initial mean stent length was 26.72% higher than nominal length and ultimate long-term tracheal mean stent shortening was only 9.90%. No significant stent migration was identified in the immediate, short-, or long-term periods. Good inter-observer agreement of radiographic measurements was found among observers of variable experience level.

CONCLUSIONS AND CLINICAL IMPORTANCE

Use of an intraluminal tracheal stent for CTCS is associated with minimal stent shortening with no clinically relevant stent migration after fluoroscopic placement. Precise stent sizing and placement techniques likely play important roles in avoiding these reported complications.

Invasive tracheal neoplasia in eight cats: descriptive cases and review of the current literature

Case series summary

This case series describes eight cases of invasive tracheal neoplasia that were recognized between the years 1989 and 2014 from a single tertiary referral hospital. This is a disproportionately high number of cases compared with the total number of reports in the current literature.

Relevance and novel information

Invasive tracheal neoplasia is uncommonly diagnosed in domestic cats. Feline tracheal tumors mimic other upper respiratory diseases making diagnosis challenging. Prognosis is guarded to grave, with most cats surviving less than 1 month after beginning treatment. Severe respiratory distress in cats often warrants humane euthanasia. Appropriate clinical suspicion and awareness can expedite diagnoses leading to prolonged survival rates with appropriate treatments. This case series represents the largest number of feline tracheal tumors reported and also describes the first unique histological presentation of what the authors believe to be a poorly differentiated tracheal carcinoma.

COMPARISON OF FLUOROSCOPY AND COMPUTED TOMOGRAPHY FOR TRACHEAL LUMEN DIAMETER MEASUREMENT AND DETERMINATION OF INTRALUMINAL STENT SIZE IN HEALTHY DOGS

Tracheal collapse is a progressive airway disease that can ultimately result in complete airway obstruction. Intraluminal tracheal stents are a minimally invasive and viable treatment for tracheal collapse once the disease becomes refractory to medical management. Intraluminal stent size is chosen based on the maximum measured tracheal diameter during maximum inflation. The purpose of this prospective, cross-sectional study was to compare tracheal lumen diameter measurements and subsequent selected stent size using both fluoroscopy and CT and to evaluate inter- and intraobserver variability of the measurements. Seventeen healthy Beagles were anesthetized and imaged with fluoroscopy and CT with positive pressure ventilation to 20 cm H2 O. Fluoroscopic and CT maximum tracheal diameters were measured by three readers. Three individual measurements were made at eight predetermined tracheal sites for dorsoventral (height) and laterolateral (width) dimensions. Tracheal diameters and stent sizes (based on the maximum tracheal diameter + 10%) were analyzed using a linear mixed model. CT tracheal lumen diameters were larger compared to fluoroscopy at all locations (P-value < 0.0001). When comparing modalities, fluoroscopic and CT stent sizes were statistically different. Greater overall variation in tracheal diameter measurement (height or width) existed for fluoroscopy compared to CT, both within and among observers. The greater tracheal diameter measured with CT and lower measurement variability has clinical significance, as this may be the imaging modality of choice for appropriate stent selection to minimize complications in veterinary patients.