History
A 2-year-old 5.6-kg (12.3-lb) sexually intact male Alaskan Klee Kai was evaluated for a sudden onset of inappetence and labored breathing of 2 days’ duration. Nonproductive gagging was noted by the owner 1 day before the initial examination. There was no history of trauma or previous problems, except an Anaplasma phagocytophylum infection diagnosed and treated by the primary veterinarian 6 weeks previously.
On physical examination, the dog was anxious, alert, responsive, cyanotic, and tachypneic (respiratory rate, 60 breaths/min [reference range, 10 to 35 breaths/min]) with inspiratory dyspnea. Severely diminished to absent broncho-vesicular sounds were noted in all lung quadrants. No heart murmurs or arrhythmias were noted. Pulses had moderate strength and were synchronous with the dog's heartbeat.
Results of a CBC and serum biochemical analyses were within reference ranges, except for slightly high serum alanine aminotransferase activity (128 U/L; reference range, 10 to 125 U/L) and phosphate concentration (8.5 mg/dL; reference range, 2.5 to 6.8 mg/dL). Findings evident on a single dorsoventral thoracic radiograph (not presented) suggested severe, bilateral lung lobe collapse and pneumothorax. Orthogonal views were not taken immediately because of the dog's severe dyspnea and agitation when attempts were made to position the dog in lateral recumbency.
The dog was sedated, and right-sided thoracocentesis was performed. Over 4 L of air was removed; however, negative pressure was not achieved. Right lateral, left lateral, and dorsoventral thoracic radiographs were obtained (Figure 1).
Dorsoventral (A), left lateral (B), and right lateral (C) radiographic views of the thorax of a 2-year-old 5.6-kg (12.3-lb) sexually intact male Alaskan Klee Kai evaluated for sudden onset of inappetence, labored breathing, and nonproductive gagging.
Citation: Journal of the American Veterinary Medical Association 254, 7; 10.2460/javma.254.7.809
Dorsoventral (A), left lateral (B), and right lateral (C) radiographic views of the thorax of a 2-year-old 5.6-kg (12.3-lb) sexually intact male Alaskan Klee Kai evaluated for sudden onset of inappetence, labored breathing, and nonproductive gagging.
Citation: Journal of the American Veterinary Medical Association 254, 7; 10.2460/javma.254.7.809
Dorsoventral (A), left lateral (B), and right lateral (C) radiographic views of the thorax of a 2-year-old 5.6-kg (12.3-lb) sexually intact male Alaskan Klee Kai evaluated for sudden onset of inappetence, labored breathing, and nonproductive gagging.
Citation: Journal of the American Veterinary Medical Association 254, 7; 10.2460/javma.254.7.809
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Radiographic Findings and Interpretation
Separation of the cardiac silhouette and sternum combined with thoracic cavity expansion, undulating deviation of the diaphragm, and collapse of the right cranial and accessory lung lobes were radiographic findings consistent with tension pneumothorax (Figure 2). In addition, an interstitial pulmonary pattern was present, and the margins of the right middle and caudal lung lobes were poorly defined. Curvilinear soft tissue margins were noted overlying the cardiac silhouette on both lateral radiographic views. Although these curvilinear soft tissue opacities could have been mediastinal reflections or aberrant tissue (freeform lines), greater complexity noted in the left hemithorax, compared with the right, suggested a lesion in the right hemithorax with left-sided atelectasis. A large, lobulated, predominantly gas opaque cystic structure with thin, peripheral soft tissue margins and multifocal striations of soft tissue opacity was evident spanning craniocaudally from the level of the carina to the diaphragm and dorsoventrally from the ventral aspect of the vertebral column to the sternebrae in the right hemithorax. The trachea, esophagus, cardiac silhouette, and other intrathoracic structures were otherwise unremarkable. A large amount of gas was noted in the gastric lumen. Severe tension pneumothorax with secondary aerophagia and atelectasis was considered the primary radiographic diagnosis. Differential diagnoses for the intrathoracic mixed opacity mass included a pulmonary bulla, spontaneous rupture of a previously healed abscess, pleural blebs, a congenital bronchogenic cyst, or a parasitic cystic structure. On the basis of the complexity of the heterogeneous tissue over the cardiac silhouette in the left hemithorax, collapse of the right cranial lung lobe, and continuous right-sided pneumothorax, a lesion that originated from the right hemithorax was strongly suspected.
Same radiographic views as in Figure 1. Diaphragmatic fattening and undulation (arrows; A), separation of the cardiac silhouette and sternum, collapsed right cranial (asterisk; A and B) and accessory (cross; A and B) lung lobes, and gas in the stomach are evidence of and consistent with tension pneumothorax and aerophagia secondary to dyspnea. In the right hemithorax, an ovoid soft tissue rim, suggestive of a cystic structure (curved lines), is evident partially summating with the cranioventral margin of the liver. An ovoid, metal opacity structure in the soft tissues just right of midline and caudal to the fourth thoracic dorsal spinous process is consistent with an identification microchip.
Citation: Journal of the American Veterinary Medical Association 254, 7; 10.2460/javma.254.7.809
Same radiographic views as in Figure 1. Diaphragmatic fattening and undulation (arrows; A), separation of the cardiac silhouette and sternum, collapsed right cranial (asterisk; A and B) and accessory (cross; A and B) lung lobes, and gas in the stomach are evidence of and consistent with tension pneumothorax and aerophagia secondary to dyspnea. In the right hemithorax, an ovoid soft tissue rim, suggestive of a cystic structure (curved lines), is evident partially summating with the cranioventral margin of the liver. An ovoid, metal opacity structure in the soft tissues just right of midline and caudal to the fourth thoracic dorsal spinous process is consistent with an identification microchip.
Citation: Journal of the American Veterinary Medical Association 254, 7; 10.2460/javma.254.7.809
Same radiographic views as in Figure 1. Diaphragmatic fattening and undulation (arrows; A), separation of the cardiac silhouette and sternum, collapsed right cranial (asterisk; A and B) and accessory (cross; A and B) lung lobes, and gas in the stomach are evidence of and consistent with tension pneumothorax and aerophagia secondary to dyspnea. In the right hemithorax, an ovoid soft tissue rim, suggestive of a cystic structure (curved lines), is evident partially summating with the cranioventral margin of the liver. An ovoid, metal opacity structure in the soft tissues just right of midline and caudal to the fourth thoracic dorsal spinous process is consistent with an identification microchip.
Citation: Journal of the American Veterinary Medical Association 254, 7; 10.2460/javma.254.7.809
Treatment and Outcome
Oxygen therapy was immediately initiated, and while still sedated, the dog received bilateral thoracostomy tubes. However, the right-sided pneumothorax did not resolve despite continuous thoracic suction for 24 hours. Differential diagnoses (mentioned previously) and diagnostic options (including thoracic CT) were discussed with the owner, and exploratory median sternotomy without further diagnostic imaging was elected. During the exploratory surgery, a large, multilobular, pink, membranous sac containing gas, clear fluid, and numerous divisions of white, fibrous tissue was identified where the right caudal lung lobe would have been normally. The right caudal lung lobe was determined to have been this cystic structure. In addition, the right cranial and middle lung lobes had atelectasis and were displaced cranially. A 30-mm vascular staplera was used to occlude the membranous sac across its base at the hilus so that the base could be transected and the membranous sac removed. Results of histologic evaluation of samples of the removed sac indicated that it contained a collapsed epithelial cystic lining supported by fibrous connective tissue and smooth muscle with disorderly plates of cartilage and glandular tissue, consistent with a congenital bronchogenic cyst.
The dog's recovery from anesthesia and surgery was uneventful. At a recheck examination 3 weeks after surgery, the sternotomy site appeared healed, and there were no other remarkable findings. Follow-up communications with the owner at 6, 9, and 12 weeks after surgery revealed that the dog had returned to its normal behaviors, including sprinting and jumping.
Comments
Bronchogenic cysts are rare abnormalities of the tracheobronchial system that usually occur during embryonic development.1 Animals clinically affected with intrathoracic forms are usually neonates (with signs of chronic, progressive restrictive airway disease [unthriftiness, coughing, poor weight gain, and dyspnea]) or young adults (with vomiting and acute or recurrent dyspnea).1–4 Findings on physical examination include tachypnea, cyanosis, and focally increased or absent lung sounds.2–4 Results of hematologic and serum biochemical analyses are usually unremarkable but can include a stress leukogram.4
Thoracic diagnostic imaging is valuable to identify bronchogenic cysts. Radiographic findings include medium-sized to large thin-walled, gas-filled structures that may have gas-fluid interfaces. In addition, compression atelectasis of surrounding lung lobes and mediastinal deviation can be present. Animals with acute onset dyspnea may have pneumothorax or tension pneumothorax (characterized by intrathoracic hyperexpansion and an increased costophrenic angle).1,2,4 Although CT has limited sensitivity to identify bullae and other causes of spontaneous pneumothorax, it can identify cavitary lesions that are not contrast enhancing and that do or do not have tracheobronchial attachment. Furthermore, bronchiectasis may be a concurrent finding.3,5,6
Histologic evaluation is required to differentiate bronchogenic cysts from other intrathoracic lesions (eg, pulmonary bullae, abscesses, pulmonary blebs, and parasitic structures). Bronchogenic cysts contain proteinaceous fluid and multiple fibrous walls of smooth muscle fibers lined with ciliated pseudostratified epithelium.2–4 Surgical excision is curative.1–3
The bronchogenic cyst of the dog in the present report originated from the right middle lung lobe. Continuous right-sided pleural space air production, radiographic findings of large amounts of gas in the right hemithorax, increased intricacy of the heterogeneous gas, and soft tissue striations overlying the cardiac silhouette on the left lateral radiographic view, compared with the right, strongly suggested that the lesion was right-sided. Additionally, the disorganized soft tissue and gas opacities evident overlying the cardiac silhouette on the left lateral thoracic view of the dog in the present report likely correspond to fibrous connective tissue, smooth muscle, and disorganized epithelia (identified on histologic examination of the cystic structure removed from the dog). Although physical and radiographic examination findings corresponded with lesion location for the dog in the present report, this is not always the case. We recommend exercising caution when planning lateralized surgical approaches for dogs with spontaneous pneumothorax.
Various techniques (eg, median sternotomy, lateral thoracotomy, and thoracoscopy) are available for exploratory surgery in patients with spontaneous, unresolving pneumothorax. In our experience, lateral thoracotomies and median sternotomies have comparable postoperative morbidity rates and recovery times; however, visualization of all pulmonary quadrants is maximized with the median sternotomy approach, which was performed on the dog in the present report. Thoracoscopy could be performed but would likely require conversion to an open technique if a large lesion that required resection was identified.
The dog in the present report had acute dyspnea, which was consistent with previous reports1–4 of bronchogenic cysts. Further, we advise veterinarians to consider rupture of a bronchogenic cyst as a differential diagnosis for spontaneous pneumothorax in young animals.
Acknowledgments
The authors declare that there were no conflicts of interest.
Footnotes
TA 30, United States Surgical Corp, Norwalk, Conn.
References
1. Berchtold B, Meylan M, Gendron K, et al. Successful treatment of an intrathoracic bronchogenic cyst in a Holstein-Friesian calf. Acta Vet Scand 2013;55:14.
2. Dahl K, Rorvik AM, Lanageland M. Bronchogenic cyst in a German Shepherd Dog. J Small Anim Pract 2002;43:456–458.
3. Gadbois J, Blond L, Lapointe C, et al. Computed tomographic evaluation of a bronchogenic cyst in a German Shepherd Dog. Can Vet J 2012;53:86–88.
4. Hiebert EC, Clarke KA, Fleming SA, et al. What is your diagnosis? J Am Vet Med Assoc 2015;247:1007–1009.
5. Lee JY, Yoon IH, Cho SW, et al. Congenital cervical bronchogenic cyst in a calf. J Vet Diagn Invest 2010;22:479–481.
6. Reetz JA, Caceres AV, Suran JN, et al. Sensitivity, positive predictive value, and interobserver variability of computed tomography in the diagnosis of bullae associated with spontaneous pneumothorax in dogs: 19 cases (2003–2012). J Am Vet Med Assoc 2013;243:244–251.
