Aerodigestive disorders in dogs evaluated for cough using respiratory fluoroscopy and videofluoroscopic swallow studies

Recognition and Diagnosis of Underlying Disease Processes in Bacterial Pneumonia

Bacterial pneumonia can present in both dogs and cats as either acute or chronic disease, and clinical signs may suggest respiratory or systemic impairment. Aspiration pneumonia, a common form of disease, can be caused by esophageal or laryngeal disease, vomiting, or altered mentation, such as with CNS disease or general anesthesia. Bacterial pneumonia can also develop due to inhaled airway foreign bodies, reduced local immune function, or impaired clearance of respiratory secretions. Rapid identification of the etiology and associated risk factors for pneumonia can help veterinarians develop a targeted therapeutic plan and prevent recurrence of disease.

Incidence and characterization of aerophagia in dogs using videofluoroscopic swallow studies

BACKGROUND

Aerophagia (ingestion of air), is a functional aerodigestive disorder in people. Criteria for diagnosis of aerophagia in dogs are >1/3 of bolus volume containing air or ingested air resulting in gastric distention (>1/3 of end gastric volume). Aerophagia is highlighted during eating and drinking. Videofluoroscopic swallow studies (VFSS) document aerophagia in dogs, but the incidence, clinical signs (CS), and associated disorders are unknown.

OBJECTIVES

Identify the incidence of aerophagia, compare CS between dogs with and without aerophagia, and identify associated and predisposing disorders using VFSS.

ANIMALS

A total of 120 client-owned dogs.

METHODS

Sequential VFSS and associated medical records from dogs presenting to veterinary teaching hospitals at Auburn University and the University of Missouri were retrospectively reviewed. Statistical comparisons were made using Mann-Whitney and chi-squared tests, odds ratios (OR), and multiple logistic regression (P < .05).

RESULTS

The incidence (95% confidence interval [CI]) of aerophagia was 40% (31.7-48.9). Dogs with mixed CS (gastrointestinal [GI] and respiratory; P < .001, 58.3%) were more likely to have aerophagia than dogs with exclusively respiratory CS (25%). Aerophagia was significantly more common in brachycephalic dogs (P = .01; 45.8% vs 13.8%), dogs with nonbrachycephalic upper airway obstruction (P < .001; 33.3% vs 4.1%), pathologic penetration and aspiration (P-A) scores (P = .04; 41.6% vs 23.6%), and gagging (P < .001; 25% vs 11.7%). Mixed CS (P = .01), brachycephaly (P < .001), and upper airway obstruction (P < .001) were independent predictors of aerophagia.

CONCLUSIONS AND CLINICAL IMPORTANCE

Aerophagia was common, particularly in dogs with mixed CS. Brachycephalic dogs and dogs with upper airway obstruction are predisposed. Aspiration risk was high, emphasizing overlapping upper aerodigestive pathways.

The respiratory microbiota and its impact on health and disease in dogs and cats: A One Health perspective

Healthy lungs were long thought of as sterile, with presence of bacteria identified by culture representing contamination. Recent advances in metagenomics have refuted this belief by detecting rich, diverse, and complex microbial communities in the healthy lower airways of many species, albeit at low concentrations. Although research has only begun to investigate causality and potential mechanisms, alterations in these microbial communities (known as dysbiosis) have been described in association with inflammatory, infectious, and neoplastic respiratory diseases in humans. Similar studies in dogs and cats are scarce. The microbial communities in the respiratory tract are linked to distant microbial communities such as in the gut (ie, the gut-lung axis), allowing interplay of microbes and microbial products in health and disease. This review summarizes considerations for studying local microbial communities, key features of the respiratory microbiota and its role in the gut-lung axis, current understanding of the healthy respiratory microbiota, and examples of dysbiosis in selected respiratory diseases of dogs and cats.

Extraesophageal reflux and reflux aspiration in dogs with respiratory diseases and in healthy dogs

BACKGROUND

Salivary bile acids are used to diagnose extraesophageal reflux (EER) and to evaluate the risk of reflux aspiration that is associated with respiratory diseases in dogs.

OBJECTIVES

To study total bile acid (TBA) concentrations in saliva and in bronchoalveolar lavage fluid (BALF) to investigate EER and reflux aspiration in dogs with respiratory diseases and in healthy dogs.

ANIMALS

 Thirty-one West Highland White Terriers (WHWTs) with idiopathic pulmonary fibrosis (IPF), 12 dogs with inflammatory airway disease (IAD), 6 dogs with recurrent pneumonia (RP), 26 brachycephalic dogs (BD), 27 healthy WHWTs (HW), 52 healthy dogs (HD). All privately-owned dogs.

METHODS

Saliva and BALF were collected from dogs in each group.

RESULTS

Salivary TBA concentrations were higher in IPF (median 0.1692 μM, interquartile range [IQR] 0.1115-0.2925 μM, Cohen's d 3.4, 95% confidence interval [CI] 2.2-4.0, P < .001) and BD (0.0256 μM, IQR 0.0086-0.0417 μM, d 0.5, CI -0.1 to 1.1, P = .003) compared to HD (0 μM, IQR not quantifiable [n.q.]-0.0131 μM). Bronchoalveolar lavage fluid TBA concentrations were higher in IPF (0.0117 μM, IQR 0.0048-0.0361 μM, d 0.5, CI 0-1.1, P < .001) compared to HD (0 μM, IQR n.q.-0.0074 μM).

CONCLUSION AND CLINICAL IMPORTANCE

Extraesophageal reflux and reflux aspiration occur in healthy dogs and those with respiratory diseases.

Incidence, clinical signs, and videofluoroscopic swallow study abnormalities associated with airway penetration and aspiration in 100 dogs

BACKGROUND

Videofluoroscopic swallow studies (VFSS) utilizing penetration-aspiration (P-A) scoring assesses airway protection in people. On VFSS, penetration (ingesta or secretions immediately cranial to the vocal folds) and aspiration (material caudal to the vocal folds) are associated with increased risk of lung injury in people. Penetration-aspiration (P-A) scoring has been validated in animal models, but the incidence of P-A, clinical signs (CS), and dysphagic disorders associated with P-A in dogs are unknown.

OBJECTIVES

Using VFSS, identify the incidence of P-A, compare CS between dogs with and without P-A, and identify predisposing dysphagic abnormalities for P-A.

ANIMALS

One hundred client-owned dogs.

METHODS

Sequential VFSS and associated medical records from dogs presenting to the veterinary teaching hospitals at Auburn University (n = 53) and the University of Missouri (n = 47) were retrospectively reviewed. Statistical comparisons were made using Mann-Whitney tests, one-way analysis of variance (ANOVA) on ranks, multiple linear regression, and Spearman rank order correlation (P < .05).

RESULTS

On VFSS, the incidence of pathologic P-A was 39%. No significant differences in CS were found between dogs with or without P-A (P > .05), with 14/39 dogs with P-A presenting without respiratory CS. Pharyngeal (P < .001) and esophageal (P = .009), but not oral-preparatory (P = .2) dysphagia was more common with P-A. Pharyngeal weakness (P < .001) and esophago-oropharyngeal reflux (EOR; P = .05) were independent predictors of P-A and were moderately and weakly positively correlated with P-A score respectively (P < .001, r = 0.489; P = .04, r = 0.201).

CONCLUSIONS

Penetration-aspiration occurs in dogs in the absence of respiratory CS (i.e., occult P-A). Dogs with pharyngeal weakness and EOR should be considered at risk for P-A.

Imaging and endoscopic diagnosis of lung diseases in small animals. A review

Diagnostic imaging plays a fundamental role in the diagnosis of pulmonary diseases. Radiography, ultrasound, computed tomography, and endoscopy are important tools for achieving a diagnosis. The choice of diagnostic procedure varies according to the patient, the suspected diagnosis and the risk/benefit ratio. Culture, cytology and histology are nearly always necessary to obtain a definitive diagnosis. Several biopsy sampling techniques are described. Surgical biopsies are the gold standard for the diagnosis of bronchiolitis or interstitial lung diseases but often not performed due to the high risk. In humans, the introduction of transbronchial cryobiopsies has led to excellent results in the study of interstitial lung diseases.

Evaluation of aerodigestive disease and diagnosis of sliding hiatal hernia in brachycephalic and nonbrachycephalic dogs

Background

Aerodigestive diseases (AeroD), hybrid disorders between the respiratory and gastrointestinal (GI) tracts, may present without GI signs. Sliding hiatal hernia (sHH) is an important AeroD in brachycephalic dogs linked to respiratory pathology. The spectrum of other AeroD and respiratory clinical signs (CS) in brachycephalic and nonbrachycephalic dogs with sHH is unknown.

Objectives

Characterize CS of AeroD in dogs with sHH, compare CS between brachycephalic and nonbrachycephalic dogs, and compare thoracic radiographs and videofluoroscopic swallow study (VFSS) for diagnosing sHH.

Animals

Sixty‐seven client‐owned dogs with sHH.

Methods

Medical records of dogs with sHH presented to the veterinary teaching hospitals at Auburn University and the University of Missouri between 1 January 2009 and 31 December 2020 were retrospectively reviewed. Between group, comparisons were made using Mann‐Whitney test, Chi‐square analysis, and Spearman correlation (P < .05).

Results

Dogs with sHH presented with exclusively GI signs (28/67), mixed respiratory and GI signs (22/67), or with exclusively respiratory signs (17/67). Wheras brachycephalic dogs were not significantly more likely to present with respiratory CS (P = .145), they were younger (P < .001), and more likely to present in respiratory distress (P = .02), and with radiographic evidence of aspiration pneumonia (P < .001) compared to nonbrachycephalic dogs. Six of 12 dogs with normal thoracic radiographs having sHH presented with respiratory CS. For detection of sHH, VFSS was superior to radiographs (P < .001).

Conclusions and Clinical Importance

Dogs with sHH may present with exclusively respiratory signs. Respiratory signs may be more severe in brachycephalic compared to nonbrachycephalic dogs. Videofluoroscopic swallow study was superior to thoracic radiographs for detection of sHH in dogs.

A Comparative Assessment of the Diagnosis of Swallowing Impairment and Gastroesophageal Reflux in Canines and Humans

Swallowing impairment is a highly prevalent and clinically significant problem affecting people and dogs. There are myriad causes of swallowing impairment of which gastroesophageal reflux is the most common in both species. Similarities in anatomy and physiology between humans and canines results in analogous swallowing disorders including cricopharyngeus muscle achalasia, esophageal achalasia, hiatal herniation, and gastroesophageal reflux with secondary esophagitis and esophageal dysmotility. Accordingly, the diagnostic approach to human and canine patients with swallowing impairment is similar. Diagnostic procedures such as swallowing fluoroscopy, high-resolution manometry, pH/impedance monitoring, and endolumenal functional luminal imaging probe can be performed in both species; however, nasofacial conformation, increased esophageal length, and the difficulty of completing several of these procedures in awake dogs are inherent challenges that need to be considered. Human patients can convey their symptoms and respond to verbal cues, whereas veterinarians must rely on clinical histories narrated by pet owners followed by comprehensive physical examination and observation of the animal eating different food consistencies and drinking water. Dogs may also be unwilling to drink or eat in the hospital setting and may be resistant to physical restraint during diagnostic procedures. Despite the species differences and diagnostic challenges, dogs are a natural animal model for many oropharyngeal and esophageal disorders affecting people, which presents a tremendous opportunity for shared learnings. This manuscript reviews the comparative aspects of esophageal anatomy and physiology between humans and canines, summarizes the diagnostic assessment of swallowing impairment in both species, and discusses future considerations for collaborative medicine and translational research.

Lower airway collapse: Revisiting the definition and clinicopathologic features of canine bronchomalacia

Bronchomalacia (BM) is an inconsistently defined term in dogs, impairing understanding of clinical presentation, therapeutic response and prognosis. Herein the authors propose to clarify the definition of canine bronchomalacia (CBM) as regional to diffuse dynamic airway collapse of segmental and/or subsegmental bronchi with associated clinical signs due to airflow limitation. In contrast to tracheal collapse, mainstem bronchial collapse, and in some cases lobar collapse, CBM requires advanced imaging. Common co-morbid conditions (e.g., chronic bronchitis, mitral valve degenerative disease, etc.) should be identified during a comprehensive diagnostic evaluation. Current empiric treatments advocated in absence of clinical trials documenting efficacy in the dog warrant evaluation, as some (e.g., bronchodilators) may have detrimental effects in certain types of airway collapse in humans. There is no direct treatment for CBM, as defined above, but non-specific therapies and targeted treatment of co-morbid disease may improve clinical signs and quality of life. In this manuscript, the authors provide a review of the different types of airway collapse focusing on CBM, reviewing their definition and etiology, proposing a classification scheme, and discussing clinical signs, diagnostic testing, and treatment. Future studies should focus on both improving understanding of the etiology and natural disease progression of CBM and treatment trials.

Aerodigestive Disease in Dogs

Aerodigestive disorders (AeroDs) in people encompass a wide range of clinical syndromes, reflecting the complex relationship between the respiratory and digestive tracts. In veterinary medicine, aspiration is used interchangeably with aspiration pneumonia. Although aspiration pneumonia is a common disorder in dogs, it does not reflect the breadth of AeroDs. Unfortunately, AeroDs rarely are investigated in veterinary medicine because of lack of clinical recognition, limitations in available diagnostics, and the fact that AeroDs may be caused by occult digestive disease. Recognizing patients with AerodD represents an area of significant clinical importance that may provide additional areas of clinical intervention.

Detection of silent reflux events by nuclear scintigraphy in healthy dogs

Background

Reflux and aspiration in people are associated with respiratory disease, whereas approximately 50% of healthy adults microaspirate without apparent consequence. In dogs, analogous information is lacking.

Hypothesis

Healthy dogs commonly have gastroesophageal reflux and a proportion of these dogs will have laryngopharyngeal reflux with silent aspiration.

Animals

Twelve healthy, client‐owned dogs.

Methods

Prospective study: Dogs were free‐fed a meal containing (111 MBq) colloidal ⁹⁹m‐technetium phytate. Dynamic‐scans were performed 5 and 30 minutes postingestion. Time‐activity curves, reflux margination, volume, frequency, and duration were evaluated over 7 regions of interest in dorsal ± left‐lateral recumbency. Static scans (dorsal recumbency) were performed 2 and 18 hours postfeeding to detect aspiration. Reflux and aspiration were defined as counts ≥200% background activity ± decreased gastric counts. Between‐group comparisons were performed by Wilcoxon rank‐sum test or one‐way ANOVA on ranks with significance of P < .05.

Results

In this study, reflux of variable magnitude was detected in 12/12 dogs. No significant differences in outcome parameters were detected with recumbency (P > .05). Margination to the pharynx and proximal, middle, and distal esophagus was identified in 5/12, 2/12, 3/12, and 2/12 dogs, respectively. Median (IQR) reflux frequency and duration were 2 events/5 minutes (1‐3.3 events/5 minutes) and 6 seconds (4‐9 seconds) respectively. No dog had detectable aspiration.

Conclusions and Clinical Importance

Nuclear scintigraphy can document reflux in dogs. Reflux, but not aspiration, is common in healthy dogs and must be considered when interpreting results in clinically affected dogs.