Endotracheal tube placement during computed tomography of brachycephalic dogs alters upper airway dimensional measurements

Computed tomography (CT) is used to document upper airway lesions in dogs with brachycephalic obstructive airway syndrome. The presence of an endotracheal tube during CT scanning is often required for general anesthesia. We hypothesized that the endotracheal tube placement would change the soft tissue dimensions of the upper airway. The aims of this prospective, method comparison study were to evaluate the reliability of the previously reported upper airway CT measurements with endotracheal tube placement, and to propose measurements that are minimally affected by the endotracheal tube. Twenty brachycephalic dogs were included in this study. Each dog underwent head/neck CT with an endotracheal tube, followed by a second scan without the endotracheal tube. Ten measurements of the soft palate, nasopharynx, and trachea were performed. Tracheal dimension was significantly larger with the endotracheal tube compared to without, whereas the soft palate cross‐sectional area was significantly smaller with the endotracheal tube than without the endotracheal tube. The influence of the endotracheal tube on the caudal nasopharynx cross‐sectional (transverse‐sectional) area varied with a mean proportional absolute difference of 35%. Rostral soft palate thickness, tracheal perimeter, and cross‐sectional area of the rostral nasopharynx were the measurements least affected by the endotracheal tube (intraclass correlation coefficient = 0.964, 0.967, and 0.951, respectively). Therefore, we proposed that these three measurements may be most useful for future brachycephalic obstructive airway syndrome studies that require CT scanning of intubated animals. However, with endotracheal tube placement, measurements of soft palate length, caudal nasopharyngeal cross‐sectional area, and trachea height and width may not be reliable.     

Use of Buccal Mucosal Flaps for the Correction of Congenital Soft Palate Defects in Three Dogs

Objective —To present an alternative surgical technique for the repair of soft palate defects in dogs.
Animal Population —Three Foxhound cross dogs.
Methods —Bilateral buccal mucosal flaps, based at the palatoglossal arches, were raised. One flap was rotated so that the mucosal side created the floor of the nasopharynx. The second flap was rotated so that the mucosal side formed the roof of the oropharynx. The mucosa of the remnant of the soft palate and the pharyngeal walls was incised and the flaps sutured to these free mucosal edges. The caudal ends of the two flaps were sutured to each other.
Results —Complete closure of the soft palate defect was obtained in all three dogs. The dogs were monitored for between 1.5 and 3 years postoperatively, and no long-term problems were encountered.
Conclusions —This surgical technique resulted in an excellent functional separation of the oropharynx and nasopharynx and allowed reconstruction of a large bilateral soft palate defect.
Clinical Relevance —By using the buccal mucosal flaps, as described in this report, a tension-free closure of large soft palate defects can be obtained, thereby eliminating a major cause of failure of this type of reconstructive surgery.     

Nasopharyngeal polyps in cats

Nasopharyngeal polyps are non-neoplastic, inflammatory growths that arise from the middle ear or the eustachian tube and extend into the pharynx. The exact etiology of nasopharyngeal polyps is unclear; proposed etiologies include a response to chronic upper respiratory tract infection, chronic otitis media, ascending infection from the nasopharynx, or a congenital origin. Clinical signs usually relate to obstruction of the nasopharynx, with Horner's syndrome and head tilt being consistent with otitis media and otitis interna, respectively. Diagnostic tools include digital or visual examination above the soft palate, flexible fiberoptic caudal rhinoscopy, radiography, computed tomography, and magnetic resonance imaging. Ventral bulla osteotomy combined with traction removal of the polyp is the recommended treatment, although traction only followed by prednisolone therapy can be considered in some cases, especially when there is no evidence of otitis media.     

Computed tomographic and radiographic bronchial collapse may be a normal characteristic of forced expiration in dogs

Tracheobronchomalacia has been diagnosed using radiography or bronchoscopy to confirm bronchial changes in luminal diameter during the respiratory cycle. However, studies in healthy humans suggest that some degree of bronchial collapse may be observed during the normal respiratory cycle. In this analytical study, the luminal diameter of the bronchus to each of the six pulmonary lobes and the mean percentage of expiratory collapse from end inspiratory, end expiratory, and two forced expiratory phases (10 and 15 ml/kg) were determined via computed tomography (CT) and radiography in 22 healthy Beagle dogs. The bronchial collapsibility was significantly greater during the forced expiration than the end expiration (P < 0.001); the same results were observed in dorsal and sagittal CT images and radiographs (P < 0.001). Median collapsibility values associated with 15 ml/kg forced expiratory collapse determined via cross‐sectional CT images were measured as 16.6–45.5% and differed according to the pulmonary lobe. Median collapsibilities on radiography with 15 ml/kg forced expiration were 57.8% and 62.1% in the right cranial lobe and right caudal lobe, respectively. In conclusion, bronchial diameter may change during the respiratory cycle, and some degree of reduction in bronchial diameter may be an incidental finding in healthy dogs. More rigorous criteria are needed with regards to bronchial collapsibility during normal respiration for the diagnosis of bronchomalacia in order to avoid false‐positive diagnoses.     

CT and radiographic evaluation of bronchial collapsibility at forced expiration in asymptomatic brachycephalic dogs

Bronchial collapse due to bronchomalacia is an important cause of chronic coughing in dogs. Radiographic and CT evidence of bronchial collapse has previously been reported in healthy Beagle dogs under forced expiration. However, published studies in brachycephalic dog breeds that are prone to bronchial collapse are currently lacking. In the present prospective analytical experimental study, CT and radiography were used to measure the bronchial diameter and collapsibility of each pulmonary bronchus during end‐expiratory, 5 mL/kg forced‐expiratory, and 10 mL/kg forced‐expiratory phases in 17 asymptomatic brachycephalic dogs and six healthy Beagle dogs. Bronchial collapsibility was significantly greater during forced expiration, than that at the end of expiration in both groups (P < .001). Bronchial collapsibility measurements of the left lung lobes and the right cranial, middle, and accessory lobes were significantly higher in asymptomatic brachycephalic dogs than those in healthy Beagle dogs, during all expiratory phases (P < .05). The higher bronchial collapsibility of brachycephalic dogs was also supported using CT multiplanar reconstruction images and radiography. In conclusion, radiographic and CT measures of bronchial collapsibility in asymptomatic brachycephalic dogs are higher than measures in healthy Beagle dogs. Therefore, measures of bronchial collapse in brachycephalic dogs should not be evaluated using the same baseline measures as those used for healthy Beagle dogs.     

Development of equine upper airway fluid mechanics model for Thoroughbred racehorses

REASON FOR PERFORMING STUDY: Computational fluid dynamics (CFD) models provide the means to evaluate airflow in the upper airways without requiring in vivo experiments. HYPOTHESIS: The physiological conditions of a Thoroughbred racehorse's upper airway during exercise could be simulated. Methods: Computed tomography scanned images of a 3-year-old intact male Thoroughbred racehorse cadaver were used to simulate in vivo geometry. Airway pressure traces from a live Thoroughbred horse, during exercise was used to set the boundary condition. Fluid-flow equations were solved for turbulent flow in the airway during inspiratory and expiratory phases. The wall pressure turbulent kinetic energy and velocity distributions were studied at different cross-sections along the airway. This provided insight into the general flow pattern and helped identify regions susceptible to dynamic collapse. RESULTS: The airflow velocity and static tracheal pressure were comparable to data of horses exercising on a high-speed treadmill reported in recent literature. The cross-sectional area of the fully dilated rima glottidis was 7% greater than the trachea. During inspiration, the area of highest turbulence (i.e. kinetic energy) was in the larynx, the rostral aspect of the nasopharynx was subjected to the most negative wall pressure and the highest airflow velocity is more caudal on the ventral aspect of the nasopharynx (i.e. the soft palate). During exhalation, the area of highest turbulence was in the rostral and mid-nasopharynx, the maximum positive pressure was observed at the caudal aspect of the soft palate and the highest airflow velocity at the front of the nasopharynx. CONCLUSIONS AND CLINICAL RELEVANCE: In the equine upper airway collapsible area, the floor of the rostral aspect of the nasopharynx is subjected to the most significant collapsing pressure with high average turbulent kinetic during inhalation, which may lead to palatal instability and explain the high prevalence of dorsal displacement of the soft palate (DDSP) in racehorses. Maximal abduction of the arytenoid cartilage may not be needed for optimal performance, since the trachea cross-sectional area is 7% smaller than the rima glottidis.     

Computed tomographic bronchial collapsibility values over 50% may be detected in healthy dogs

Bronchomalacia and bronchial collapse are important causes of chronic coughing in dogs. The current reference standard diagnostic tests for these problems are flexible bronchoscopy and biopsy. Previous human studies have also supported inspiration/expiration computed tomography (CT) as a diagnostic test. The current prospective, pilot study aimed to determine whether inspiration/expiration CT is also a feasible test for quantifying bronchial collapsibility in dogs. Thoracic CT images were acquired using a 64‐row multidetector CT for 10 healthy Beagle dogs during maximal inspiration and expiration. For each scan, one observer measured transverse sectional areas of the mainstem and lobar bronchi, and the dorsal and ventral segmental bronchi of the left cranial lobar bronchus. Diameters for each bronchus were also measured in transverse, sagittal, and dorsal planes. Bronchial collapsibility (%) was calculated as the difference between inspiration/expiration transverse sectional areas divided by the inspiration transverse sectional areas. Mean bronchial collapsibility of all bronchi was 38.20 ± 15.17%. A collapsibility of over 50% was found in the dorsal (n = 7) and ventral (n = 4) segmental bronchi of the left cranial lobar bronchus, and the left caudal (n = 5) and right middle (n = 2) lobar bronchus. Bronchial collapsibility measurements were greater in the dorsal and ventral segmental bronchi of the left cranial lobar bronchus and the left caudal lobar bronchus (P < 0.001). Findings supported inspiration/expiration CT as a modality to noninvasively assess bronchial collapse in dogs and a bronchial collapsibility value greater than 50% for detecting pathologic bronchial collapse in clinically affected dogs.     

Quantification of nasal airflow resistance in English bulldogs using computed tomography and computational fluid dynamics

Stenotic nares, edematous intranasal turbinates, mucosal swelling, and an elongated, thickened soft palate are common sources of airflow resistance for dogs with brachycephalic airway syndrome. Surgery has focused on enlarging the nasal apertures and reducing tissue of the soft palate. However, objective measures of surgical efficacy are lacking. Twenty‐one English bulldogs without previous surgery were recruited for this prospective, pilot study. Computed tomography was performed using conscious sedation and without endotracheal intubation using a 128 multidetector computed tomography scanner. Raw multidetector computed tomography data were rendered to create a three‐dimensional surface mesh model by automatic segmentation of the air‐filled nasal passage from the nares to the caudal soft palate. Three‐dimensional surface models were used to construct computational fluid dynamics models of nasal airflow resistance from the nares to the caudal aspect of the soft palate. The computational fluid dynamics models were used to simulate airflow in each dog and airway resistance varied widely with a median 36.46 (Pa/mm)/(l/s) and an interquartile range of 19.84 to 90.74 (Pa/mm)/(/s). In 19/21 dogs, the rostral third of the nasal passage exhibited a larger airflow resistance than the caudal and middle regions of the nasal passage. In addition, computational fluid dynamics data indicated that overall measures of airflow resistance may significantly underestimate the maximum local resistance. We conclude that computational fluid dynamics models derived from nasal multidetector computed tomography can quantify airway resistance in brachycephalic dogs. This methodology represents a novel approach to noninvasively quantify airflow resistance and may have utility for objectively studying effects of surgical interventions in canine brachycephalic airway syndrome.     

Otitis media in five cats associated with soft palate abnormalities

The medical records of five cats that were diagnosed with otitis media and soft palate abnormalities, three of which had concurrent otitis interna, were reviewed retrospectively. The animals presented with unilateral or bilateral otitis media or otitis interna associated with soft palate hypoplasia (four cases) or unilateral soft palate cleft (one case). Otitis media was confirmed by radiography, CT or MRI. The soft palate abnormalities present were discovered on oropharyngeal examination at induction of anaesthesia. These five cases provide additional support of a link between otitis media and soft palate abnormalities in cats, as reported in humans and dogs.     

Embryonal rhabdomyosarcoma in an immature Baird's tapir (Tapirus bairdii).

An immature Baird's tapir (Tapirus bairdii) with a history of seizure-like episodes developed signs of respiratory disease. The initial clinical diagnosis was pneumonia, and antibiotic therapy was started. The animal failed to improve after 14 days of therapy and developed unilateral, bloody nasal discharge. Endoscopic examination and radiography revealed a soft tissue mass in the nasopharynx depressing the soft palate. The tapir died 32 days after initial presentation. Histologic examination of the mass demonstrated a mesenchymal tumor composed of spindle cells with elongate nuclei forming densely packed fascicles. The neoplastic spindle cells showed prominent cross-striations. Immunohistochemistry revealed the cells to be positive for desmin and myoglobin, but negative for smooth muscle actin, confirming diagnosis of rhabdomyosarcoma. Embryonal rhabdomyosarcoma is the most common nasopharyngeal soft tissue tumor of humans, and it has been reported infrequently in dogs, horses, and pigs. Neoplasia should be a differential diagnosis in cases of unilateral nasal discharge and inspiratory stridor, even in young animals.     

Use of a mucosal advancement flap for the treatment of nasopharyngeal stenosis in a cat

A three-and-a-half-year-old male neutered domestic short-haired cat was presented with a three-year history of stertor and intermittent open-mouth breathing. No airflow was detected from either nostril when checked using a cold slide test. Oropharyngeal swabs were positive for calicivirus, while skull radiographs were suggestive of a dorsal deviation of the soft palate. The diagnosis of nasopharyngeal stenosis was confirmed via cannulation of the nasal passages and direct examination of the oropharynx under general anaesthesia. A midline approach through the soft palate was used to excise the adhesions. The resulting defect was reconstructed by advancement of a mucosal flap elevated from the dorsal nasopharynx and laryngopharynx. The cat was free of clinical signs 28 months later.     

COMPUTED TOMOGRAPHY OF THE PHARYNX IN A CLOSED VS. OPEN MOUTH POSITION

The pharynx is anatomically complex and evaluation can be difficult even with cross‐sectional imaging. Eight animals had computed tomography (CT) studies of the head performed with the mouth open and closed. The studies were anonymized and evaluated by four radiologists for visibility of six anatomic regions (dorsal wall of nasopharynx, lumen of nasopharynx, dorsal margin of the soft palate, ventral margin of the soft palate, oropharynx, and laryngopharynx) and for certainty of a normal or abnormal diagnosis of four different anatomic regions (nasopharynx, soft palate, oropharynx, and laryngopharynx). Mean visual scores differed significantly between mouth positions and were improved when the mouth was open. The ability of radiologists to classify anatomic regions as normal or abnormal vs. unsure also varied between mouth positions, and there was greater uncertainty when the mouth was closed. In addition, estimated volume of the air‐filled nasopharynx differed significantly as a function of mouth position and was greater when the mouth was open (mean=1.187 cm³, SE=0.177) vs. closed (mean=0.584 cm³, SE=0.116). Computed tomographic evaluation of the pharynx can be improved with the mouth open.     

COMPARISON BETWEEN COMPUTED TOMOGRAPHIC AND SURGICAL FINDINGS IN NINE LARGE-BREED DOGS WITH LUMBOSACRAL STENOSIS

In a three-year prospective study, computed tomographic (CT) and surgical findings were compared for nine large breed dogs with lumbosacral stenosis. Surgically-excised tissue was examined histologically in seven dogs and additional necropsy evaluation was performed in one dog. The CT abnormalities observed at sites of confirmed cauda equina compression were: loss of epidural fat, increased soft tissue opacity, bulging of the intervertebral disc margin, spondylosis, thecal sac displacement, narrowed intervertebral foramen, narrowed vertebral canal, thickened articular process, articular process subluxation, articular process osteophyte, and telescoped sacral lamina. The CT characteristics of lumbosacral degenerative disease and discospondylitis were similar to those described in humans. In three dogs, CT findings at the site of cauda equina compression were consistent with congenital or developmental spinal stenosis, but the method of surgical exposure precluded confirmation. Epidural fibrosis (eight dogs) and multi-level CT abnormalities (six dogs) were identified but the cause(s) and significance were unknown.     

IMAGING DIAGNOSIS—PORTAL VEIN APLASIA AND INTERRUPTION OF THE CAUDAL VENA CAVA IN THREE DOGS

Severe portal vascular anomalies have been reported previously accompanying azygos continuation of the caudal vena cava, polysplenia, and situs anomalies in dogs and people. Three dogs with portal vascular anomalies were identified by means of CT angiography as having portal vein aplasia with portal insertion into the caudal vena cava, azygos continuation of the caudal vena cava, and interruption of the pre‐hepatic caudal vena cava. This information confirms that complex embryological defects may occur in patients presenting for congenital portosystemic shunt, and that CT angiography is a non‐invasive method of completely evaluating these potentially non‐surgical portal vascular anomalies.     

A histopathological comparison of two techniques for soft palate resection in normal dogs

Eighteen dogs were used to compare histopathological findings following excision of the soft palate using either a bipolar sealing device or a carbon dioxide laser. Histopathological comparisons were done at 48 and 96 hours after soft palate resection. Mean depths of tissue injury at 96 hours were 3.5 and 3.33 mm for bipolar sealing device and carbon dioxide laser, respectively. Control of hemorrhage was excellent in all dogs, and none of the dogs developed signs of respiratory compromise after soft palate resection. Using the bipolar sealing device for soft palate resection was significantly faster than using the carbon dioxide laser, although both techniques were fast.     

First case of salivary mucocele originating from the minor salivary gland of the soft palate in a dog

We found a case of salivary mucocele that originated in the minor salivary gland (palatine gland) of the soft palate in a dog. At first admission, the soft palate swelled remarkably. Computed tomography (CT) revealed cystic radiolucency inside a large quantity of liquid in the soft palate, and most of the airway was occupied. Marsupialization was performed, but since a recurrence was observed one month later, the salivary mucocele was removed. There has been no report of salivary mucocele arising from the minor salivary gland of the soft palate in dogs. To our knowledge, this case is the first. Complete removal, including minor salivary glands surrounding the lesion, is necessary for treatment of salivary mucocele in dogs.     

Pleomorphic sarcoma with giant cells infiltrating the infraorbital canal in an aged Thoroughbred mare

A 27-year-old Thoroughbred mare presented for computed tomography (CT) of the head following a 3-month history of facial swelling at the infraorbital foramen, unilateral self-mutilation and head-shaking. Standing CT imaging showed soft tissue attenuation surrounding the infraorbital canal, with extensive bony lysis of the canal and maxillary bone at the infraorbital foramen. The mare was subjected to euthanasia, and post-mortem examination revealed a proliferative tan soft tissue mass overlying the infraorbital nerve. A histopathological diagnosis of pleomorphic sarcoma with giant cells was made. Immunohistochemical analysis failed to fully elucidate the mesenchymal cell of origin of the sarcoma. Pleomorphic sarcoma with giant cells involving the infraorbital canal of the horse has not been previously described. This case highlights chronic subtle behavioural changes attributable to this neoplasm prior to the development of clinical signs and the utility of advanced imaging in the diagnosis.