COMPUTED TOMOGRAPHIC IMAGING OF DOGS WITH PRIMARY LARYNGEAL OR TRACHEAL AIRWAY OBSTRUCTION

Seventeen dogs with clinical signs attributable to nonneoplastic obstruction of the larynx, trachea, or large bronchi underwent computed tomography (CT) imaging. In 16 of the 17 dogs, CT was performed without general anesthesia using a positioning device. Fifteen of these 16 dogs were imaged without sedation or general anesthesia. Three‐dimensional (3D) internal rendering was performed on each image set based on lesion localization determined by routine image planes. Visual laryngeal examination, endoscopy, video fluoroscopy, and necropsy were used for achieving the cause of the upper airway obstruction. The CT and 3D internal rendering accurately indicated the presence and cause of upper airway obstruction in all dogs. CT findings indicative of laryngeal paralysis included failure to abduct the arytenoid cartilages, narrowed rima glottis, and air‐filled laryngeal ventricles. Laryngeal collapse findings depended on the grade of collapse and included everted laryngeal saccules, collapse of the cuneiform processes and corniculate processes, and narrowed rima glottis. Trachea abnormalities included hypoplasia, stenosis, or collapse syndrome. The CT findings in tracheal hypoplasia consisted of a severely narrowed lumen throughout the entire length. Tracheal stenosis was represented by a circumferential decrease in tracheal lumen size limited to one region. Tracheal collapse syndrome was diagnosed by severe asymmetric narrowing. Lobar bronchi collapse appeared in CT images as a narrowed asymmetric lumen diameter. CT imaging of unanesthetized dogs with upper airway obstruction compares favorably with traditional definitive diagnostic methods.     

IMAGING DIAGNOSIS—EQUINE NASAL SEPTAL THICKENING DUE TO CHRONIC CHONDRITIS

We describe the use of computed tomography (CT) in a 6-year-old mare with upper airway obstruction due to an abnormally thick nasal septum. Upon CT imaging, multifocal, expansile cyst-like lesions were detected in the nasal septum. The histopathologic diagnosis was chronic dissecting chondritis. Resection of the abnormal nasal septum resulted in resolution of the clinical signs.     

THORACIC COMPUTED TOMOGRAPHY IN FELINE PATIENTS WITHOUT USE OF CHEMICAL RESTRAINT

Computed tomography (CT) and thoracic radiography were performed in nonsedated, nonanesthetized, cats with thoracic disease. The final diagnosis was obtained with echocardiography, cytology, histopathology, necropsy, or response to therapy. For CT imaging, cats were in a positioning device using a 16 multislice helical CT system. Fifty‐four cats had CT imaging of which 50 had thoracic radiography. The most common diagnoses were lung neoplasia, lower airway disease, and cardiomyopathy (nine each). Other disease groups included mediastinal mass (eight), infection (seven), trauma (four), and hernia (three). CT provided additional correct diagnoses in 28% (14/50) and additional information in 74% (37/50) of the cats. Additional correct diagnoses achieved only with CT were most common for cats with lower airway disease. The most common additional findings with CT were lung nodules (n=4), lung masses (n=4), bronchiectasis (n=4), and mediastinal lymphadenopathy (n=3). Survey CT led to a significant different diagnosis or different prognosis in 20 of the 50 cats that were imaged both modalities. Contrast CT was performed in 19 cats, most commonly in cats with lung neoplasia (n=6), a mediastinal mass (n=4) or an infection (n=3), and provided additional correct diagnosis in two cats not achieved with survey CT. Thoracic CT using a positioning device in diseased awake cats is feasible, safe, and clinically useful.     

COMPARISON BETWEEN 2‐18F‐FLUORO‐2‐DEOXY‐D‐GLUCOSE POSITRON EMISSION TOMOGRAPHY AND CONTRAST‐ENHANCED COMPUTED TOMOGRAPHY FOR MEASURING GROSS TUMOR VOLUME IN CATS WITH ORAL SQUAMOUS CELL CARCINOMA

Feline oral squamous cell carcinoma is one of the most refractory feline malignancies. Most patients succumb due to failure in local tumor control. 2‐¹⁸F‐fluoro‐2‐deoxy‐D‐glucose positron emission tomography (¹⁸F‐FDG PET) is increasingly being used for veterinary oncology staging as it highlights areas with higher glucose metabolism. The goal of the current prospective study was to compare gross tumor volume measurements using ¹⁸F‐FDG PET vs. those using computed tomography (CT) for stereotactic radiation therapy planning in cats with oral squamous cell carcinoma. Twelve cats with confirmed oral squamous cell carcinoma underwent pretreatment ¹⁸F‐FDG PET/CT. Gross tumor volumes based on contrast‐enhanced CT and ¹⁸F‐FDG PET were measured and compared among cats. Mean PET gross tumor volume was significantly smaller than mean CT gross tumor volume in the mandibular/maxillary squamous cell carcinoma group (n = 8, P = 0.002) and for the total number of patients (n = 12, P = 0.006), but not in the lingual/laryngeal group (n = 4, P = 0.57). Mismatch fraction analysis revealed that most of the lingual/laryngeal patients had a large region of high‐¹⁸F‐FDG activity outside of the CT gross tumor volume. This mismatch fraction was significantly greater in the lingual/laryngeal group than the mandibular/maxillary group (P = 0.028). The effect of poor spatial resolution of PET imaging was greater when the absolute tumor volume was small. Findings from this study indicated that ¹⁸F‐FDG PET warrants further investigation as a supplemental imaging modality in cats with oral squamous cell carcinoma because it detected regions of possible primary tumor that were not detected on CT images.     

Radiographic and computed tomographic appearance of caseous lymphadenitis in a goat

A 2‐year‐old Boer doe was presented with respiratory distress and severe inspiratory dyspnea. Cervical and thoracic radiographs revealed a marked retropharyngeal soft tissue mass effect, several mineralized pharyngeal and retropharyngeal structures, and a pulmonary mass. Computed tomography (CT) revealed a severely enlarged right medial retropharyngeal lymph node, which caused laryngeal compression, leading to upper airway obstruction. Multiple cervical and thoracic lymph nodes, and the pulmonary mass had an irregular layered/laminated pattern of mineralization. Imaging findings were consistent with caseous lymphadenitis, and further confirmed with culture, necropsy, and histopathology. This is the first report of CT appearance of caseous lymphadenitis in a goat.     

Advances in diagnostic imaging of the larynx and pharynx

Imaging of the larynx and pharynx has traditionally been limited to upper airway endoscopy and radiography. Recently, ultrasonography, magnetic resonance imaging and computed tomography have become used more widely. These modalities have increased our diagnostic yield when investigating disorders of the upper airway. The Case Report in this issue ( Koenig et al. 2012 ) describes the diagnosis and biopsy of a laryngeal mass using ultrasonography illustrating one novel application of laryngeal ultrasonography. Increased use of laryngeal ultrasonography and advanced imaging of the larynx and pharynx will hopefully lead to a better understanding of conditions of the upper airway and improved treatment strategies.     

Evaluation of a modified castellated laryngofissure for alleviation of upper airway obstruction in dogs with laryngeal paralysis

A modified castellated laryngofissure procedure (castellated laryngofissure, vocal fold resection, and bilateral arytenoid lateralization) was performed on 12 dogs with bilateral laryngeal paralysis. Clinical signs of airway obstruction were assessed and a pulmonary function test (tidal breathing flow volume loop) was used to evaluate the severity of obstruction. The dogs were evaluated before surgery and at various periods from 4 days to 15 months after surgery. One dog died immediately after surgery and 3 dogs died due to nonrelated or unknown causes 1, 9, and 11 months after surgery. Clinical signs of upper airway obstruction disappeared or decreased in severity in the 11 dogs that recovered from surgery. Tidal breathing flow volume loop values were normal in 7 of 10 dogs evaluated within 5 to 189 days after surgery. The modified castellated laryngofissure procedure provided successful long-term relief of upper airway obstruction associated with bilateral laryngeal paralysis.     

Laryngeal paralysis in cats: 16 cases (1990-1999)

OBJECTIVE: To determine clinical signs, physical examination findings, radiographic features, and concurrent diseases in cats with laryngeal paralysis, as well as evaluate the outcome of medical or surgical management. DESIGN: Retrospective study. ANIMALS: 16 cats. PROCEDURE: Medical records from January 1990 to April 1999 were examined for cats with laryngeal paralysis. Signalment, clinical signs, physical examination findings, cervical and thoracic radiographic findings, laryngeal examination results, and clinical outcome were reviewed. RESULTS: No breed or sex predilection was identified in 16 cats with laryngeal paralysis. The most common clinical signs included tachypnea or dyspnea, dysphagia, weight loss, change in vocalization, coughing, and lethargy. Clinical signs were evident for a median of 245 days. Airway obstruction was apparent on cervical and thoracic radiographic views in 9 cats. Examination of the larynx revealed bilateral laryngeal paralysis in 12 cats and unilateral laryngeal paralysis in 4 cats. The 4 cats with unilateral disease were managed with medical treatment, and 3 of these had acceptable long-term outcomes. Seven of 12 cats with bilateral paralysis underwent surgery; procedures performed included left arytenoid tie back, bilateral arytenoid tie back and ventriculo-cordectomy, and partial left arytenoidectomy. One cat was euthanatized as a result of complications from surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Laryngeal paralysis is an uncommon cause of airway obstruction in cats. Cats with less severe clinical signs (often with unilateral paralysis) may be successfully managed with medical treatment, whereas cats with severe airway obstruction (often with bilateral paralysis) may benefit from surgical intervention.     

Acute Upper Airway Obstruction Due to Inflammatory Laryngeal Disease in 5 Cats

Objective: To describe a clinical syndrome of upper airway obstruction in 5 cats due to inflammatory laryngeal disease.
Series Summary: Medical records of 5 cats with upper airway obstruction and a histopathologic diagnosis of inflammatory laryngeal disease were reviewed. Historical findings included: dyspnea, anorexia, voice change, and gagging/non-productive retching. Thoracic radiographs revealed a bronchial pattern in 2 cats, with consolidation of the right middle lung lobe in one cats. Laryngeal examinations typically revealed severe swelling and erythema which could not be grossly distinguished from neoplasia. Histopathologic examination of laryngeal biopsies revealed neutrophilic (n=5) and lymphoplasmacytic (n=4) inflammation. All of the cats were treated with corticosteroids and 4 cats received antibiotics. Two cats died while hospitalized, one was discharged and lost to follow-up, and 2 are doing well 7 months and 4 years later, respectively.
New information provided: Inflammatory laryngeal disease in cats may present as an acute upper airway obstruction. These cases may respond to corticosteroids and antibiotics, and some cases may have an excellent long-term prognosis.( J Vet Emerg Crit Care 2001; 11(3): 205–211 )     

COMBINATION OF COMPUTED TOMOGRAPHIC IMAGING CHARACTERISTICS OF MEDIAL RETROPHARYNGEAL LYMPH NODES AND NASAL PASSAGES AIDS DISCRIMINATION BETWEEN RHINITIS AND NEOPLASIA IN CATS

Feline nasal diseases are a diagnostic challenge. The objective of this retrospective, cross‐sectional study was to determine whether computed tomography (CT) imaging characteristics of the medial retropharyngeal lymph nodes (MRPLN), alone or in combination with CT imaging characteristics of the nasal passages, could aid in differentiation between rhinitis and nasal neoplasia. Cats were recruited from record archives at two veterinary facilities during the period of 2008–2012. Selection criteria were presentation for chronic nasal discharge, contrast‐enhanced CT of the head that included the MRPLN, and rhinoscopic nasal biopsy resulting in diagnosis of rhinitis or neoplasia. For each CT scan, two board‐certified veterinary radiologists recorded MRPLN size, attenuation, heterogeneity, contrast‐medium enhancement, margination, shape, presence of a lymph node hilus, perinodal fat, turbinate lysis, paranasal bone lysis, and nasal mass. Both readers were unaware of patient information at the time of CT interpretation. Thirty‐four cats with rhinitis and 22 cats with neoplasia were included. Computed tomographic characteristics significantly associated with neoplasia included abnormal MRPLN hilus (OR 5.1), paranasal bone lysis (OR 5.6), turbinate lysis (5.6), mass (OR 26.1), MRPLN height asymmetry (OR 4.5), and decreased MRPLN precontrast heterogeneity (OR 7.0). The combined features predictive of neoplasia were a nasal mass with abnormal hilus (OR 47.7); lysis of turbinates/paranasal bones with abnormal MRPLN hilus (OR 16.2). Findings supported the hypothesis that combining CT features of the nasal passages and MRPLN aided in differentiating rhinitis from neoplasia in cats.     

Tracheostomy in cats: 23 cases (1998-2006)

Tracheostomies can be used to provide a patent airway in animals with upper airway obstruction but have been reported to be more difficult to manage in cats than in other animals. The purpose of this study is to retrospectively describe the indications, complications and outcome of cats undergoing tracheostomy. Twenty-three cats underwent tracheostomy for laryngeal mass (n=13), trauma (n=5) and upper airway swelling (n=5). Major and minor complications were recorded in 10 and 17 cats, respectively. Seventeen cats were discharged to home, four cats were euthanased and two cats died in hospital. Complications with stoma healing were reported in one cat. Of seven cats discharged with a permanent tracheostomy, one cat is alive and six cats survived at home for between 2 and 281 days. Although complications are common, temporary tracheostomies can be beneficial for conditions in which the underlying cause can be treated. Despite risk of occlusion, permanent tracheostomies can be effective palliative procedures for cats with severe upper airway disease.     

COMPUTED TOMOGRAPHIC APPEARANCE OF INFLAMMATORY POLYPS IN THREE CATS

This report describes the use of computed tomography (CT) to evaluate the inner ear, tympanic bullae, nasopharyngeal area, and external ear canals of three cats. All cats presented for evaluation of upper respiratory signs or chronic ear infection. Nasopharyngeal masses were present in two cats, and a mass in the external ear canal was present in the third cat. In all three cats, CT was able to define the extent of osseous bulla involvement, which was confirmed at surgery. Computed tomography also defined the extent of the polyp in the nasopharyngeal area in two cats, and in the external ear canal in one cat. Surgical removal of the polyps was accomplished with a combined oral approach and ventral bulla osteotomy in cats 1 and 2. The polyp was removed from cat 3 using a combination of ventral bulla osteotomy and excision of the mass through the external ear canal. Microscopic examination confirmed all masses as nasopharyngeal (inflammatory) polyps.     

Evaluation of unilateral arytenoid lateralization for the treatment of laryngeal paralysis in 14 cats

Laryngeal paralysis is a relatively common cause of upper airway obstruction in middle-aged to older, large-breed dogs; however, it is rare in the cat. The purpose of this study is to describe a series of cats diagnosed with laryngeal paralysis treated by unilateral arytenoid lateralization. Fourteen cats met the criteria of the study. Intraoperative and postoperative complications were seen in 21% (three of 14) and 50% (seven of 14) of cases, respectively. Median duration of follow-up was 11 months (range 3 weeks to 8 years). None of these cats had recurrence of clinical signs. Based on this brief case series, unilateral arytenoid lateralization appeared to be a suitable method for treating laryngeal paralysis in cats. Additional studies are warranted to determine the type and frequency of long-term complications.     

ACCURACY OF CT AND MRI FOR CONTOURING THE FELINE OPTIC APPARATUS FOR RADIATION THERAPY PLANNING

Consistency and accuracy in normal tissue contouring in radiotherapy planning is important for comparison of dosimetry and toxicity data between studies. The purpose of this study was to determine whether magnetic resonance imaging (MRI) improves the accuracy of optic apparatus contouring as compared with computed tomography (CT) in both normal and acromegalic cats, and to construct a reference contour of the feline optic apparatus. Both CT and MRI were performed on cadavers of four healthy cats, as well as on five radiotherapy patients with feline acromegaly. Contours of the optic apparatus were drawn for each imaging study. The volume, center of mass, and the degree of concordance and mismatch were determined for each, and compared with a reference standard. Precontrast CT was found to overestimate volume as compared with MRI in acromegalic cats; no other statistically significant differences were identified in the volume, concordance index or mismatch index values of normal or acromegalic cats. Contours derived from T2‐wieghted MRI were subjectively considered to best match the reference standard. The caudal margin of the optic chiasm and the optic tracts were difficult to confidently contour regardless of which imaging modality and/or sequence was used. In conclusion, findings from the current study supported the use of a combination of CT and MR images and a priori knowledge of the shape of the optic apparatus to guide accurate contouring, especially where image contrast is not sufficient to clearly delineate the margins. Guidelines for feline optic apparatus contouring developed in this study can be used for future studies.     

IMAGING DIAGNOSIS—NASAL SEPTAL AND LARYNGEAL CYST‐LIKE MALFORMATIONS IN A THOROUGHBRED WEANLING COLT DIAGNOSED USING ULTRASONOGRAPHY AND MAGNETIC RESONANCE IMAGING

A foal was examined for abnormal upper airway noise. Endoscopically, there were narrowed nasal passages and an extralumenal mass of the cranial trachea. Using ultrasonography and magnetic resonance (MR) imaging of the larynx and cranial cervical trachea, irregular margins of the laryngeal cartilages and first tracheal ring containing areas consistent with fluid were identified. In MR images, a widened nasal septum was seen that contained material consistent with fluid. Postmortem examination confirmed the diagnosis of nasal septal, laryngeal, and cranial cervical tracheal cyst‐like lesions. This is a unique congenital condition, in which premortem imaging was instrumental in defining the abnormalities.     

Evaluation of a stented laryngoplasty for correction of cranial glottic stenosis in four dogs

After laryngeal surgery, cranial glottic stenosis secondary to laryngeal web formation was diagnosed as the cause of upper airway obstruction in 4 dogs. Initial treatment of 3 dogs by peroral laryngeal web excision resulted in rapid recurrence of clinical signs. Subsequently, these 3 and the fourth dog were treated by scar excision, mucosal flap coverage, and placement of a silicone intraluminal laryngeal stent for 14 days. By 5 months (average) after surgery, on the basis of clinical evaluation of exercise intolerance, respiratory distress, and stridor, all dogs had alleviation of upper airway obstruction.     

Nasopharyngeal turbinates in brachycephalic dogs and cats

This retrospective study reports the presence and incidence of nasal turbinates in the nasopharynx (nasopharyngeal turbinates) in a population of brachycephalic dogs and cats exhibiting signs of upper respiratory disease. Medical records were reviewed for 53 brachycephalic dogs and 10 brachycephalic cats undergoing upper airway endoscopy. Nasopharyngeal turbinates were identified in 21% of brachycephalic animals, including 21% of dogs and 20% of cats. Pugs accounted for 32% of all dogs in the study population and 82% of dogs with nasopharyngeal turbinates. The presence of nasopharyngeal turbinates may play a role in upper airway obstruction in the brachycephalic airway syndrome.     

Prevalence of clinical and subclinical middle ear disease in cats undergoing computed tomographic scans of the head

Three hundred and ten cats that had CT imaging of the head between January 2000 and December 2007 were evaluated retrospectively. Data that were recorded included signalment, presenting complaint, clinical signs, presence of upper respiratory tract disease, and CT findings. One hundred and one cats had evidence of middle ear disease on CT. Thirty-four of the 101 cats (34%) did not have a primary complaint of ear-related disease, clinical signs or physical findings consistent with ear disease, suggesting that the middle ear disease was subclinical. Twenty-seven of the 34 cats (79%) had concurrent nasal disease. Middle ear lesions were chronic in appearance. With the exception of tympanic bulla lysis, CT findings were similar in cats presenting with primary aural disease versus cats with presumptive subclinical middle ear disease. The majority of the cats did not return for treatment of the identified middle ear abnormalities. Subclinical middle ear disease is relatively frequent in cats undergoing CT imaging of the head. Few cats required subsequent treatment for ear disease although follow up was limited. Identification of subclinical middle ear abnormalities on CT should prompt acquisition of a detailed patient history and bilateral otoscopic examination.