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

Stents in Veterinary Medicine

Stenting in veterinary medicine has been a rapidly growing method of interventional surgery for several years. This procedure is usually performed in the respiratory and urinary tracts, but there are cases of stenting of blood vessels or gastrointestinal structures. It is based on maintaining the permeability of a given tubular structure, thus allowing the passage of gas or liquid. This procedure is often performed as a first-line treatment in situations where pharmacological agents do not work and as an alternative method, often cheaper than the classically performed ones. There are also cases where stenting is used as a palliative treatment, e.g., to enable defecation in colonic obstruction due to tumour infiltration of the colon wall. Stenting is often a life-saving or comfort-improving procedure for animals, but one should also be aware of possible postoperative complications and be prepared for any adversity. For this reason, this review provides an insight into the current knowledge in veterinary medicine about stenting and the consequences associated with this procedure.

Retrospective analysis of tracheal hypoplasia in brachycephalic and non-brachycephalic dogs: Inter- and intra-observer agreement of measurements

This retrospective study was undertaken on the records of intraluminal diameter of the trachea in 185 dogs, in which hypoplasia of the trachea had been suspected. The relative size of the trachea was measured using the tracheal diameter (TD), thoracic inlet distance (TI), thoracic tracheal diameter (TT) and the width of the third rib (3R), expressed as ratios TD:TI and TT:3R. Thirty-five dogs were diagnosed as having tracheal hypoplasia. Bulldogs and non-bulldog brachycephalic dogs had significantly smaller measured trachea diameters compared to the predicted values calculated on the basis of their body weight. Radiographs of each dog were investigated by four observers. Inter- and intra-observer reliability (ICCinter, ICCintra) was based on the measurements taken by four observers to evaluate the reproducibility of the protocol. There was a good ICCinter (0.8) and ICCintra (0.89) agreement. Craniocaudal tangential radiographs, centred on the cranial thoracic aperture, did not show a significant difference in tracheal diameter measurements compared to the right lateral radiographs. In conclusion, our findings indicate that bulldogs and non-bulldog brachycephalic dogs have smaller tracheal diameters than non-brachycephalic dogs.

Imaging in neonatal respiratory disease

The purpose of this review is to describe the current state of the art in clinical imaging for NICU patients, divided into major areas that correspond to likely phenotypes of neonatal respiratory disease: airway abnormalities, parenchymal disease, and pulmonary vascular disease. All common imaging modalities (ultrasound, X-ray, CT, and MRI) are discussed, with an emphasis on modalities that are most relevant to the individual underlying aspects of disease. Some promising aspects of dynamic and functional imaging are included, where there may be future clinical applicability.

Use of computational fluid dynamics to compare upper airway pressures and airflow resistance in brachycephalic, mesocephalic, and dolichocephalic dogs

Brachycephalic dog breeds are prone to breathing difficulties because of their upper airway anatomy. Several surgical techniques exist to correct anatomical pathologies and common surgical approaches aim to correct functional abnormalities in the nares and/or the soft palate. However, further research is needed to improve clinical outcomes. This study evaluated air pressure and airflow resistance in the upper airways and trachea in nine sedated, sternally recumbent dogs of different skull types (dolichocephalic, n=3; mesocephalic, n=3; brachycephalic, n=3). CT images were acquired from the nostrils to the caudal border of the lungs and geometrical reconstruction of the upper airway and trachea was performed. Analysis of computational fluid dynamics was performed using inspiratory flow adapted to bodyweight for each dog. Flow (L/min) and pressure (cmH₂O) were computed for the entire upper airway and trachea. Resistance (cmH₂O/L/min) was calculated using pressure differences between the nose, larynx, and trachea. In this pilot study, statistical comparisons were not performed. Pressure maps, airflow, and resistance were similar in dolichocephalic and mesocephalic breeds. Median pressure difference (3.76cmH₂O) and resistance (0.154cmH₂O/L/min) between the nose and larynx were numerically higher in brachycephalic dogs than in other breeds (0.45cmH₂O and 0.016cmH₂O/L/min, respectively). Median pressure difference (0.205cmH₂O) and resistance (0.009cmH₂O/L/min) between the larynx and trachea was numerically similar in all dogs, except for the English bulldog. The methodology used in this preliminary study to quantify airflow characteristics such as pressure and resistance could improve the understanding of brachycephalic obstruction airway syndrome.

Application of Micro-Tech stents in malignant carinal stenosis

Malignant carinal stenosis is a disease process that is not always suitable for treatment with a Y-shaped stent. When one of the main bronchi is completely obstructed and cannot be recanalized, or its distal lung tissue has lost function, inserting a Y-shaped stent is infeasible. In this complex condition, a cone-shaped stent is selected to maintain the patency of the trachea and the other main bronchus. The efficacy of the bare cone-shaped Micro-Tech stent to treat malignant carinal stenosis was evaluated in the current study. The medical records of 47 patients with malignant carinal stenosis who underwent Micro-Tech stent placement between January 2004 and October 2017 in Beijing Tian Tan Hospital (Beijing, China) were analyzed retrospectively. A total of 47 bare Micro-Tech stents (28 Y-shaped and 19 cone-shaped) were successfully inserted in the patients. Following stent placement, immediate satisfactory results were achieved in all patients, especially an improvement of dyspnea (100%), cough (81.1%) and stridor (100%). The Karnofsky scores were significantly increased (P<0.001), and the American Thoracic Society Dyspnea Index values were significantly decreased (P<0.001). Following a median of 88 days, initial bronchoscopic interventions were performed for tumor overgrowth (84.6%), stent fracture (7.7%) and granulation tissue (7.7%). Restenting was performed in two patients due to tumor progression (n=1) and stent fracture (n=1). Removal of a Y-shaped stent was attempted in one patient, but failed, as the stent had become partly embedded in the airway mucosa. In conclusion, cone-shaped Micro-Tech stent placement maintained tracheal-unilateral main bronchus patency and benefitted patients with malignant carinal stenosis in whom Y-shaped stents were not suitable for insertion.