Retrospective evaluation of traumatic pneumomediastinum in dogs and cats (2005-2022): 52 cases.

OBJECTIVE: To describe the incidence, etiology, clinical signs, diagnostics, treatments, and outcome of noniatrogenic traumatic pneumomediastinum (TPM) in dogs and cats. DESIGN: Retrospective study of cases (2005-2022). SETTING: University veterinary teaching hospital. ANIMALS: Fifty-two patients (29 dogs, 23 cats). MEASUREMENTS AND MAIN RESULTS: Data collected from the medical records included signalment, physical examination findings, animal trauma triage (ATT) score, clinicopathological data, imaging data, surgical intervention, length of hospitalization, supportive care, complications, and outcome. Most dogs presented with tachycardia and tachypnea, while cats presented with hypothermia and tachypnea. Subcutaneous emphysema, pneumothorax, and dyspnea were the most common clinical signs for both species. The median calculated ATT score was 3.5 in dogs and 4 in cats. The most common radiographic abnormalities other than pneumomediastinum were pneumothorax and lung contusions. The overall mortality rate was 18%, with a significantly higher survival rate in dogs (26/28 dogs [93%], 15/22 cats (68%); P = 0.03). Outcome was unknown in 1 dog and 1 cat. The only significant difference in treatment between survivors and nonsurvivors was the requirement in dogs for positive pressure ventilation. The median hospitalization period was 2 days for both species, with a shorter hospitalization in the nonsurvivors (0.6 vs 2 days, respectively; P = 0.006). CONCLUSIONS: TPM is an infrequent pathology in veterinary medicine and may be seen without an externally obvious injury. The most common causes for TPM in dogs were vehicular trauma and bite wounds, while high-rise syndrome was the most common cause in cats. Most of the cases have concurrent pneumothorax and require thoracocentesis; however, direct intervention to treat TPM is not usually required. The vast majority of cases did not undergo surgery to treat TPM. The prognosis for dogs with TPM was good but was guarded for cats.

Air leak syndrome in animals: definition and pathogenesis.

Air leak syndrome (ALS) is described in human medicine as a constellation of clinical disorders including pneumomediastinum, pneumopericardium, pulmonary interstitial emphysema, pneumothorax, pneumoperitoneum, pneumoretroperitoneum and subcutaneous emphysema. The pathogenesis of ALS depends on the anatomy of the mediastinum and its associations with thoracic, abdominal and cervical connective tissues, as well as a physical phenomenon referred to as the Macklin effect. Various animal species develop diverse combinations of these lesions, although ALS has not been recognized in animals. However, this term aids pathologists in addressing this disease compilation. The aim of this retrospective study is to illustrate examples of ALS in animals by arbitrarily selecting 13 cases in dogs, cats, pinnipeds, sea otters and harbour porpoises. ALS can be classified into three groups based on aetiology: iatrogenic, secondary or spontaneous. Iatrogenic ALS was diagnosed in two cats with tracheal laceration following endotracheal intubation. Secondary ALS was identified in two dogs, one with acute respiratory distress syndrome and the other due to grass awn migration. Secondary ALS in pinnipeds was diagnosed following severe pulmonary parasitism, uraemic pneumonia and oesophageal perforation. The other marine mammals developed ALS following trauma. Spontaneous ALS was also diagnosed in one cat and one dog without any apparent predisposing causes.

Pulmonary interstitial emphysema and spontaneous pneumomediastinum are more prevalent in sighthounds than other dog breeds undergoing thoracic CT.

Spontaneous pneumomediastinum is an uncommon condition described in veterinary medicine with concurrent respiratory disease. It can be caused by the Macklin effect, which is when gas leaks from the alveoli into the surrounding interstitial lung tissue. Pulmonary interstitial emphysema (PIE) is the presence of gas within the pulmonary vascular sheaths and indicates the presence of the Macklin effect. In the authors' experience, spontaneous pneumomediastinum and PIE are more prevalent in sighthound dogs than in other breeds and are often considered incidental findings. This retrospective, observational, cross-sectional study compared the prevalence of PIE and subsequent pneumomediastinum in sighthound with other purebred dogs. It characterized the appearance of PIE in CT and analyzed a possible association with concomitant pulmonary pathologies or with the use of general anesthesia. Medical records and thoracic CTs of sighthounds and nonsighthound dogs from two institutions were reviewed. A total of 256 dogs, comprising 127 sighthounds and 129 other purebred dogs, were included. The prevalence of PIE and pneumomediastinum was statistically higher in sighthound (14.2%) compared with other nonsighthound dogs (2.2%). There was no statistical association between the presence of PIE and pneumomediastinum with different age and weight groups or with sex. There was no statistical difference in the prevalence of PIE and pneumomediastinum between dogs with and without pulmonary pathology or in dogs undergoing CT with sedation or general anesthesia. Spontaneous pneumomediastinum in sighthounds is more prevalent than in other breeds, and its prevalence is not associated with the presence of pulmonary pathology or the use of general anesthesia.

The successful use of a subcutaneous catheter in the management of severe subcutaneous emphysema in a dog with laryngeal crush injury and tracheostomy tube placement.

OBJECTIVE: To describe the placement of a subcutaneous catheter in a dog for the management of severe subcutaneous emphysema secondary to severe laryngeal crushing injury and temporary tracheostomy tube placement. CASE SUMMARY: A 6-year-old male neutered Kelpie suffered a severe laryngeal crushing injury following a dog attack. Case management included the placement of a temporary tracheostomy tube due to severe respiratory compromise and inspiratory dyspnea associated with the crush injury. During hospitalization, the patient developed severe subcutaneous emphysema, pneumomediastinum, and a pneumothorax as a complication of the laryngeal crushing injury and temporary tracheostomy. A subcutaneous catheter was placed to manage the recurrent subcutaneous emphysema while the tracheostomy stoma healed. Five months posttrauma, the dog returned to normal with mild stridor during excitement and while panting. NEW OR UNIQUE INFORMATION PROVIDED: This is the first report in veterinary medicine describing the use of a subcutaneous catheter for the management of subcutaneous emphysema secondary to laryngeal crush injury and temporary tracheostomy tube placement.

Subcutaneous emphysema and pneumomediastinum following orbital blowout pathological fracture in a cat with nasal lymphoma: a case report.

BACKGROUND: Subcutaneous emphysema and pneumomediastinum are rare complications associated with orbital blowout pathological fracture. CASE PRESENTATION: A 7-year old, castrated male Abbysinian cat presented with anorexia, lethargy, nausea, eyelid swelling, nasal discharge, and sneezing. Based on the clinical and diagnostic work-up, the cat was diagnosed with T cell high-grade nasal lymphoma associated with orbital pathological fracture due to the tumour invasion. After chemotherapy, the cat showed massive subcutaneous emphysema from frontal region to abdomen and pneumomediastinum due to orbital blowout pathological fracture. As the nasal mass decreased in volume; the air had moved from the maxillary sinus to the subcutaneous region and the mediastinum through fascial planes in the head and neck region. CONCLUSIONS: This is a first case report of a massive subcutaneous emphysema and pneumomediastinum due to an orbital blowout pathological fracture following chemotherapy in feline nasal lymphoma in veterinary medicine.

Oesophageal pneumatosis: computed tomographic characteristics in three dogs (2018-2021).

BACKGROUND: Oesophageal pneumatosis (OP) is defined as the presence of gas within the oesophageal wall. The description of this condition in veterinary medicine is currently lacking. The pathogenesis of alimentary tract pneumatosis remains unclear. Current literature describes that access of gas into the oesophageal wall may occur by one or a combination of the following mechanisms: mucosal disruption, increased intra or extra-luminal pressure or dissection of gas from an extra-oesophageal source. OBJECTIVES: The aim of this multi-centric case series was to describe the computed tomography (CT) findings of OP in dogs. METHODS: Three adult dogs were included. One dog presented with gastrointestinal signs and general malaise while the other two presented with spontaneous facial and cervical subcutaneous emphysema. RESULTS: CT revealed different degrees of intramural gas along the oesophageal wall in all cases. The first dog was diagnosed with emphysematous gastritis based on the presence of gastric pneumatosis paired with compatible clinicopathological and endoscopic findings. This dog was successfully treated with antibiotics. The remaining two dogs were diagnosed with spontaneous pneumomediastinum and required no surgical or medical treatment. CONCLUSIONS: In all cases with OP, there was concurrent gastric pneumatosis. Gas extensively and circumferentially distributed with a banded shape along the oesophageal wall was present in patients with presumed mural gas dissection because of pneumomediastinum. Conversely, a focal and mild amount of mural gas with a tubular shape was identified in the distal segment of the oesophagus in the patient with emphysematous gastritis.

Cervical tracheal rupture with persistence of a pseudotrachea in a dog.

A dog was examined because of acute onset of respiratory distress following a cervical dog bite. Physical examination revealed a deep ventral cervical bite wound associated with localized mild subcutaneous emphysema. Thoracic radiographs showed moderate pneumomediastinum. Medical management consisting of oxygen therapy, antibiotics, and anti-inflammatories was initiated. After 2 days, respiratory distress suddenly worsened. Tracheoscopy showed a discontinuity between the tracheal rings of the cervical trachea; however, the inner tracheal wall appeared intact. Computed tomography scan revealed a ~3-cm complete rupture of all layers of the trachea. Surgical resection and anastomosis of the trachea were performed successfully. Follow-up 15 days after surgery showed complete resolution of respiratory signs, as well as subcutaneous emphysema. A mild ventral angulation of the trachea at the surgical site was noticed on thoracic radiographs. This is the first case report of a pseudotrachea in a dog. Persistence of a pseudotrachea may initially result in only minor clinical signs responsive to medical therapy despite tracheal rupture. In the presence of a pseudotrachea, tracheal rupture may be difficult to identify with tracheoscopy alone. Therefore, CT scan should be proposed in every patient with suspected tracheal trauma. Key clinical message: This case report highlights the importance of including a tracheal rupture in the differential diagnosis of cervical subcutaneous emphysema, even if the amount is small and not associated with significant respiratory signs. The presence of a pseudotrachea may result in less severe clinical signs than expected based on the actual degree of tracheal injury; however, the clinical status may rapidly deteriorate and become life-threatening. This case report also underlines the importance of a CT scan as a complement to tracheoscopy, which may not be sufficient to identify a tracheal rupture in the presence of a pseudotrachea.

Rupture trachéale cervicale avec persistance d'une pseudotrachée chez un chien. Un chien a été présenté pour une dyspnée aiguë modérée consécutive à des morsures cervicales par un autre chien. L'examen clinique révéla une plaie cervicale ventrale profonde associée à un emphysème sous-cutané localisé léger. Les radiographies thoraciques ont montré un pneumomédiastin modéré. Un traitement médical consistant en une oxygénothérapie, des antibiotiques et des anti-inflammatoires a été initié. Après deux jours, la dyspnée s'aggrava brutalement. Une trachéoscopie révéla une discontinuité entre les anneaux trachéaux malgré la persistance d'une paroi trachéale interne intègre. L'examen par tomodensitométrie montra une rupture trachéale cervicale complète dans toute son épaisseur, sur 3 cm de long. Une chirurgie de résection-anastomose de la trachée a été réalisée avec succès.Il s'agit de la première description de pseudotrachée chez un chien. La persistance d'une pseudotrachée peut initialement ne provoquer que des signes cliniques mineurs, notamment un emphysème sous-cutané léger et une dyspnée répondant au traitement médical, malgré une lésion trachéale en réalité importante. Par conséquent, un examen par tomodensitométrie de la trachée doit être envisagé chez tous les patients pour lesquels un traumatisme trachéal est suspecté.Message clinique clé :Ce cas souligne l'importance d'inclure une rupture trachéale dans le diagnostic différentiel de l'emphysème souscutané cervical, et cela même s'il n'est présent qu'en petite quantité et associé à faibles signes cliniques respiratoires. La persistance d'une pseudotrachée peut entraîner des signes cliniques moins importants qu'une rupture trachéale complète, cependant l'état respiratoire de l'animal peut rapidement s'aggraver et devenir une urgence vitale.Ce cas souligne de plus l'importance de l'examen par tomodensitométrie en complément de la trachéoscopie, qui peut parfois s'avérer insuffisante pour le diagnostic des ruptures trachéales, en particulier en présence d'une pseudotrachée.(Traduit par les auteurs).

Pneumoperitoneum as an uncommon complication after an axillary laceration in a horse.

Lacerations of the axillary region occur frequently in horses. Typical complications caused by entrapment of air in the wound during locomotion are subcutaneous emphysema, with consecutive pneumomediastinum and pneumothorax. In this case report, the clinical, radiographic and laboratory diagnosis and management of these complications after an axillary laceration that finally resulted in pneumoperitoneum are described. A 1-year-old Hannoveranian was presented with a pre-existing axillary laceration of unknown duration and subcutaneous emphysema in the surrounding tissue. Due to extensive tissue loss, attempts to adequately close the wound surgically and by packing with sterile dressing material were unsuccessful. Despite stall confinement and tying of the horse, subcutaneous emphysema was progressive and pneumomediastinum as well as pneumothorax was developed. These complications were monitored radiographically. On day 5 after admission, signs of air accumulation were detected on radiographs craniodorsally in the peritoneum and a pneumoperitoneum was diagnosed. Repeated thoracentesis with a teat cannula to gradually evacuate the thoracic cavity was used in combination with nasal oxygen insufflation to treat global respiratory insufficiency. Subcutaneous emphysema and all other complications resolved progressively and the horse was discharged from the hospital 21 days after admission when the axillary wound was adequately filled with granulation tissue. The wound healed fully 1 month later and the horse did not develop long-term complications within the following year. To the authors´ knowledge, the development of pneumoperitoneum including its radiographic monitoring following an axillary laceration has not been described in horses previously.

Thoracic radiographic features of fatal paraquat intoxication in eleven dogs.

BACKGROUND: Paraquat (1,1-dimethyl-4,4-bipyridinium dichloride) is a toxic herbicide. Accidental ingestion of paraquat in animals and humans causes respiratory failure and death. AIM: To describe the radiographic features of confirmed paraquat intoxication in a group of dogs and determines whether any identified features can facilitate this diagnosis. METHODS: Eleven dogs diagnosed with paraquat intoxication were selected from two institutions between November 2014 and August 2019 comprising five males (all intact) and six females (one intact and five spayed). The mean age was 3.9 ± 2.9 (SD) years and their mean weight was 11.6 ± 5.0 kg. The tentative diagnosis was confirmed through analysis of their urine samples using a colorimetric assay (paraquat concentation 0.39 µg/ml ranging from 0.19-0.65 µg/ml), and their clinical signs were reviewed. Thoracic radiographs were evaluated for the presence of pneumomediastinum, lung patterns (interstitial or alveolar) and their locations (caudodorsal, cranioventral, diffuse, or symmetrical), subcutaneous emphysema, pneumoretroperitoneum, and pneumothorax. RESULTS: The most common clinical signs were dyspnea (11/11, 100%) and anorexia (9/11, 82%). Pneumomediastinum (10/11, 91%) and symmetrically increased lung opacity (7/11, 65%) were the most common radiographic features. Pneumothorax (3/11, 27%), pleural effusion (3/11, 27%), subcutaneous emphysema (2/11, 18%), and pneumoretroperitoneum (1/5, 20%) were the less common findings. None of the dogs survived. CONCLUSION: Pneumomediastinum and diffuse or symmetrical interstitial or alveolar lung patterns are the most common radiographic features in dogs with paraquat intoxication. CLINICAL RELEVANCE: In countries where this herbicide is not banned, paraquat intoxication should be considered if dogs with no history of trauma present with pneumomediastinum.

Development of a tension pneumomediastinum during mechanical ventilation of a young Irish Wolfhound.

OBJECTIVE: To report the development of a tension pneumomediastinum during mechanical ventilation of a young Irish Wolfhound with aspiration pneumonia. CASE SUMMARY: A 9-month-old intact female Irish Wolfhound was presented for clinical signs consistent with aspiration pneumonia. Evaluation of her pedigree and clinical signs prompted suspicion of Irish Wolfhound rhinitis bronchopneumonia syndrome as a contributing factor. Despite supportive care for bronchopneumonia, progressive hypoxemia and increased work of breathing required mechanical ventilation (MV). Development of a pneumothorax 36 hours after initiation of MV necessitated bilateral thoracostomy tubes. Cardiovascular decline persisted despite resolution of the pneumothorax and 1 hour later the dog was humanely euthanized. On necropsy, severe pneumomediastinum was identified without other evidence of barotrauma. Necropsy results suggested tension pneumomediastinum as the cause of pneumothorax and cardiovascular deterioration. NEW OR UNIQUE INFORMATION PROVIDED: Pneumomediastinum has not been described in dogs receiving MV. This case highlights the importance of rapid detection of pneumomediastinum during MV, as the complication can quickly become life-threatening.

Computed tomographic findings in a Bluetick Coonhound with a longitudinal thoracic tracheal tear.

A 9-year-old intact male Bluetick Coonhound presented for progressive subcutaneous emphysema of 5 days' duration due to a suspected tracheal tear. Cervical computed tomography (CT) and thoracic CT were performed after failure to identify the tracheal tear with tracheoscopy. A longitudinal tracheal tear was identified starting 4.3 cm cranial to the tracheal bifurcation and extending caudally over a distance of 3.6 cm. Severe pneumomediastinum, subcutaneous emphysema, and retroperitoneal gas were also present. A follow-up CT 7 days postoperatively confirmed the successful repair of the tear with partial resolution of the presurgical secondary pathology and the patient recovered uneventfully.

Pneumomediastino, pneumotórax e enfisema subcutâneo em cão com pneumopatia e infecção pelo vírus da cinomose: relato de caso / Pneumomediastinum, pneumothorax and subcutaneous emphysema in a dog with pneumopathy and infection by the canine distemper virus: case report

Relata-se um caso de pneumomediastino, pneumotórax e enfisema subcutâneo em um cão com pneumopatia associada à cinomose. As queixas principais eram tosse, secreção nasal purulenta, apatia e enfisema subcutâneo em face, região cervical e torácica. O exame radiográfico evidenciou pneumomediastino, pneumotórax e broncopneumopatia grave com áreas de consolidação pulmonar. Teste rápido imunocromatográfico para detecção de antígeno da cinomose foi positivo e houve melhora dos sinais respiratórios com antibioticoterapia, porém o quadro evoluiu para alterações neurológicas. De acordo com a revisão de literatura realizada, não há casos semelhantes relatados.(AU)

A case of pneumomediastinum, pneumothorax and subcutaneous emphysema in a dog with pneumopathy associated to distemper is reported. The main complaints were cough, purulent nasal discharge, lethargy and subcutaneous emphysema in the face, neck, and chest area. Radiographic examination showed pneumomediastinum, pneumothorax, and severe bronchopneumopathy with areas of pulmonary consolidation. Rapid test for canine distemper antigen detection was positive. After the antibiotic therapy there was an improvement of respiratory signs; however, the patient developed neurological symptomatology. As far as the author´s knowledge by literature review carried out, there are no similar cases reported.(AU)

Pneumocystis carinii infection with severe pneumomediastinum and lymph node involvement in a Whippet mixed-breed dog.

A 3.5-y-old Whippet mixed-breed dog was presented with a history of respiratory distress, exercise intolerance, and generalized demodicosis. Hematologic alterations included marked leukocytosis and neutrophilia. Radiographic examination showed a diffuse interstitial and mild peripheral alveolar lung pattern and pneumomediastinum. Because the cytologic examination of the bronchoalveolar aspirate was not diagnostic and a persistent perforation of the upper respiratory tract could not be ruled out, the dog was submitted to thoracoscopy, and subsequently the left cranial lung lobe as well as mediastinal and sternal lymph nodes were resected. Pulmonary pneumocystosis with spread to the thoracic lymph nodes was suspected after histologic investigation of lung and lymph nodes, which was confirmed by in situ hybridization, PCR, and subsequent Sanger sequencing. We document a rare, simultaneous occurrence of severe pulmonary and thoracic lymph node pneumocystosis with spontaneous pneumomediastinum in a dog. Definitive diagnosis was achieved through the use of Grocott methenamine silver staining, in situ hybridization, and PCR.

Traumatic lung injury attributed to tornadic activity-induced barometric pressure changes in two dogs.

CASE DESCRIPTION A 7-year-old castrated male Italian Greyhound (dog 1) and an approximately 1-year-old female Labrador Retriever (dog 2) were evaluated because of respiratory distress 8 and 10 days, respectively, after a tornado. CLINICAL FINDINGS No obvious external injuries were identified auscultation revealed decreased bronchovesicular sounds in the affected hemithorax of both dogs. Clinicopathologic changes were mild, with evidence of inflammation in both dogs. Thoracic radiography of both dogs revealed pneumothorax and pleural effusion with effacement of the diaphragm; findings on CT included severe pulmonary atelectasis of affected lung lobes with normal bronchial tree configurtion and no evidence of diaphragmatic hernia. TREATMENT AND OUTCOME Exploratory thoracotomy of both dogs confirmed CT findings Pulmonary parenchymal damage consistent with a large rupture was found in both patients. A large hematoma was adhered to the ruptured lung lobe of dog 1. Grossly affected lung tissue was removed; histologic examination revealed atelectasis, pulmonary fib osis, thrombosis, and minimal (dog 1) to marked (dog 2) inflammation Microbial culture of lung tissue yielded no growth for dog 1 and Streptococcus spp and Escherichia coli susceptible to amoxicillin-clavulanic acid for dog 2. Dog 1 had a recurrence of pneumothorax treated by drainage with a thoracostomy tube 1 month after surgery. Eighteen months after surgery, both dogs were reportedly doing well. CLINICAL RELEVANCE Development of clinical signs after a tornado, together with clinical, diagnostic imaging, surgical, and histologic findings led to a presumptive diagnosis of pulmonary barotrauma for both dogs. Long-term outcome for these dogs, treated at a referral hospital, was good.

Congenital lobar emphysema concurrent with pneumothorax and pneumomediastinum in a dog.

A two-year-old castrated male Pomeranian dog was referred with the chief complaints of coughing and subcutaneous emphysema. On physical examination, the crepitant areas were palpable. When auscultated, the right chest was absent of respiratory sound, while the sound of the opposite side was enhanced. Radiographs presented pneumothorax and pneumomediastinum. On computed tomography, hypoattenuated bulla-like lesion at right middle lung lobe and trapped air in mediastinum were shown. After patient stabilization, surgery for excision of affected lobe was performed. During follow-up period, there were no recurrence and complication on radiographic examination. Based on clinical and pathological findings, the dog was diagnosed as congenital lobar emphysema.

Pneumopericardium Secondary to Pneumomediastinum in a Golden Retriever Dog.

Pneumopericardium is a rare finding that has been previously reported following spontaneous, traumatic, or iatrogenic causes. A 3-year old Golden Retriever dog was admitted with respiratory distress after falling from a height. Clinical and electrocardiographic findings were nonspecific. Thoracic radiography revealed hyperinflated lung with sharp outlining of the mediastinal structures. A well-demarcated region of radiolucent gas opacity was seen surrounding the cardiac silhouette. Echocardiography revealed intense hyper-reflective shadows all over the heart. Echocardiographic measurements were within the reference range. The dog responded well to conservative medical therapy. Pneumopericardium was reported secondary to pneumomediastinum; pneumopericardium is self-limiting unless other complications develop.

Pneumopericardium, pneumomediastinum, pneumothorax and pneumoretroperitoneum complicating pulmonary metastatic carcinoma in a cat.

This report describes a case of severe spontaneous tension pneumopericardium with concurrent pneumomediastinum, pneumothorax and retropneumoperitoneum in a cat presenting with dyspnoea and signs of cardiac tamponade secondary to metastatic pulmonary carcinoma. Spontaneous pneumopericardium is an extremely uncommon condition consisting of pericardial gas in the absence of iatrogenic/traumatic causes. In humans, it has been described secondary to pneumonia or lung abscess and very rarely secondary to pulmonary neoplasia.

IMAGING DIAGNOSIS-SPONTANEOUS PNEUMOMEDIASTINUM SECONDARY TO PRIMARY PULMONARY PATHOLOGY IN A DALMATIAN DOG.

A 1.5-year-old, 23 kg intact male Dalmatian dog was evaluated for acute respiratory insufficiency without a previous history of trauma or toxic exposition. Imaging revealed pneumomediastinum, pneumothorax, diffuse unstructured interstitial pulmonary pattern, pulmonary interstitial emphysema, and pneumoretroperitoneum. Histopathological evaluation of the lungs revealed perivascular and peribronchial emphysema, mild lymphocytic interstitial pneumonia with atypical proliferation of type II pneumocytes in bronchioles and alveoli. A lung disease resembling fibrosing interstitial pneumonia in man and cats has been previously reported in Dalmatians and should be included as a differential diagnosis for Dalmatians with this combination of clinical and imaging characteristics.

Pneumomediastinum in cats: 45 cases (2000-2010).

OBJECTIVE: To characterize the incidence, etiology, presenting complaint, clinical course, and outcome of cats with pneumomediastinum. DESIGN: Retrospective study from the period of January 1st, 2000 to December 31st, 2010. SETTING: University teaching hospital. ANIMALS: Forty-five cats with a radiographic diagnosis of pneumomediastinum. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Medical and radiographic records were reviewed to identify cats with a radiographic diagnosis of pneumomediastinum. Clinical data were retrieved, including signalment, history, presenting clinical signs, diagnostic test results, treatment, complications, and survival to discharge. In 31 of 45 (69%) cats the pneumomediastinum was secondary to an obvious inciting cause. General anesthesia with endotracheal intubation and positive pressure ventilation was the most common cause in 17 of 45 (38%) cases. This was followed by trauma in 12 of 45 (27%) cats, and tracheal foreign bodies in 2 of 45 (4%) cats. Spontaneous pneumomediastinum (unknown underlying cause) was diagnosed in 14 of 45 (31%) of cases. Onset of clinical signs and diagnosis of spontaneous pneumomediastinum was preceded by emesis in 6 of 14 cats. Common presenting signs were tachypnea seen in 27 of 45 (60%) cats, increased respiratory effort in 26 of 45 (58%) cats, and subcutaneous emphysema in 30 of 45 (66%) cats. Concurrent pneumothorax was identified in 21 of 45 (47%) cats, pleural effusion in 10 of 45 (22%), and pneumoretroperitoneum in 21 of 45 (47%). The mainstay of treatment was supportive care and treatment of the underlying disease process. The prognosis for recovery was good, with 87% survival until hospital discharge. CONCLUSIONS: Pneumomediastinum in cats is an infrequently diagnosed condition. It is often secondary to an event such as general anesthesia with endotracheal intubation and positive pressure ventilation but less frequently may occur spontaneously. The prognosis is good with appropriate supportive care.