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Lindsey M. Kurach Guardian Veterinary Centre, 5620 99th St, Edmonton, AB, Canada.

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Stephanie G. Nykamp Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.

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P. Brendon Ringwood Veterinary Emergency Clinic and Referral Centre, 920 Yonge St, Toronto, ON M4W 3C7, Canada.

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 DVM, MS, DACVS

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History

A 3-year-old neutered male Cocker Spaniel was evaluated because of a 1-day history of trembling and dyspnea. The dog also had a 3-month history of once-weekly retching and vomiting after eating a large amount of food. On physical examination, the dog was tachypneic and dyspneic. Thoracic auscultation revealed vesicular lung sounds on the left and diminished lung sounds on the right. Heart sounds were muffled on the right. No murmur was auscultated. Abnormalities on CBC included mild anemia and mild leukocytosis, characterized by neutrophilia, monocytosis, and basophilia. Serum biochemical analysis revealed mildly low urea and chloride concentrations. Thoracic radiographs were obtained (Figure 1).

Figure 1—
Figure 1—

Left lateral (A) and ventrodorsal (B) radiographic views of the thorax of a 3-year-old neutered male Cocker Spaniel evaluated because of a 1-day history of dyspnea and tachypnea.

Citation: Journal of the American Veterinary Medical Association 241, 9; 10.2460/javma.241.9.1149

Determine whether additional imaging studies are required, or make your diagnosis from Figure 1then turn the page

Diagnostic Imaging Findings and Interpretation

In both the left and right pleural spaces, there is effusion, resulting in retraction of the lung borders from the thoracic wall and pleural fissure lines. In the right cranial and right middle lung lobes, there are soft tissue opacities that silhouette with the pulmonary blood vessels and create air bronchograms. These lung lobes are enlarged, with the right middle lobe having a rounded margin. Gas bubbles are scattered throughout the right cranial and middle lung lobes (vesicular emphysematous lung pattern; Figure 2). On the ventrodorsal view, the bronchus of the right middle lung lobe is oriented caudally. On the lateral view, the bronchus to the right cranial lung lobe is focally narrowed at the hilus.

Figure 2—
Figure 2—

Same radiographic images as in Figure 1. Severe, bilateral pleural effusion is obscuring the cardiac silhouette. In the right cranial and right middle lung lobes, there are soft tissue opacities that silhouette with the pulmonary blood vessels and create air bronchograms (asterisks). Pleural effusion has caused retraction of the lung borders from the thoracic wall, creating pleural fissure lines (arrows). There is an abrupt tapering of the right mainstem bronchus (arrowhead). A vesicular emphysematous lung pattern can be seen within these areas as well.

Citation: Journal of the American Veterinary Medical Association 241, 9; 10.2460/javma.241.9.1149

Thoracocentesis of the right pleural space was performed after the initial findings on thoracic radiography, yielding approximately 550 mL of serosanguineous fluid. Results of cytologic evaluation of the fluid were consistent with a modified transudate. Aerobic and anaerobic microbial culture of this fluid did not yield any growth. Thoracic radiography was repeated (images not shown) after thoracocentesis. Mild bilateral pleural effusion remained. Two soft tissue opacities, corresponding to the cardiac silhouette and the affected lung lobes, were present. The vesicular emphysematous lung patterns were still present in the right cranial and right middle lung lobes.

Computed tomography was performed, which revealed consolidation and enlargement of the right cranial and right middle lung lobes with vesicular emphysema and air bronchograms (Figure 3). This resulted in atelectasis and medial deviation of the right caudal lung lobe. At the hilus of the right cranial and right middle lung lobes, the bronchi were completely compressed. In addition, postcontrast CT failed to enhance the vasculature of these affected lobes. These findings were consistent with lung lobe torsions of both the right cranial and right middle lung lobes.

Figure 3—
Figure 3—

Precontrast transverse CT image (3-mm-thick slices; 120 kVp; 250 mA) obtained at the level of the sixth thoracic vertebrae (A) and a dorsal plane reformatted CT image (B) of the thorax of the dog in Figure 1. The lung lobes were enlarged and consolidated (1) with multiple gas attenuating foci corresponding to a vesicular emphysematous pattern (2). A mild amount of pleural fluid was still present (3). Compression of the bronchus of the right cranial lung lobe was evident (4); the bronchus of the left cranial lung lobe was normal in appearance (5).

Citation: Journal of the American Veterinary Medical Association 241, 9; 10.2460/javma.241.9.1149

Treatment and Outcome

The diagnosis of lung lobe torsion was confirmed during thoracotomy, and lobectomies of the abnormal lobes were performed. The dog recovered from anesthesia and surgery uneventfully. Histologic evaluation of the right cranial and middle lung lobes revealed severe, subacute, diffuse hemorrhage and necrosis with mild neutrophilic inflammation and early pleural fibrosis, consistent with lung lobe torsions.

Comments

Lung lobe torsions are an uncommon pulmonary condition involving twisting of the lobe around its bronchus. This causes bronchial obstruction and vascular compromise, resulting in congestion of the lung lobe.1 Torsions, most commonly affecting the right middle lung lobe, have been reported primarily in large, deep-chested breeds. Lung lobe torsions have also been observed in small-breed, chondrodystrophic, and toy-breed dogs, in which the left cranial lung lobe is most often affected.2 Multiple lung lobe torsions, as in the dog of the present report, are rare. Lung lobe torsion may develop secondary to trauma, pleural effusion, diaphragmatic hernias, or pneumothorax.3 In many cases, including that of the dog of the present report, the cause is not known.

The most common radiographic findings of lung lobe torsion are increased lobar opacity and pleural effusion, followed by vesicular emphysema1; however, these findings are not specific for lung lobe torsion. Vesicular emphysema is associated with necrosis of the lung lobe and can be caused by lung lobe torsion, neoplasia invading the pulmonary artery, or severe infection.1 Affected lobes may be consolidated (enlarged or normal size) or atelectatic (small).1,4 Narrowing of the bronchi or an abnormal orientation of the bronchi are also seen with lung lobe torsions.1 All of these radiographic characteristics were observed in the dog of the present report. Because of multiple lung lobe involvement, the opacities within the lung field were more prominent, compared with a single lobe torsion. Computed tomography is a useful imaging tool in suspected cases of lung lobe torsion if radiographic findings are not definitive. Common findings on CT include bronchial tapering and narrowing or collapse, pleural effusion, failure of the affected lung lobe to enhance with contrast, and a vesicular emphysematous lung pattern, which is more obvious than may be seen with radiographs.4,5 In the dog of the present report, CT was particularly useful to obtain a definitive diagnosis because torsions of multiple lung lobes are uncommon.

The recommended treatment for lung lobe torsion is surgical excision of the affected lung lobe. Approximately 50% of treated dogs will recover without complication, and toy-breed dogs have a better prognosis than do large-breed dogs.3

  • 1. D'Anjou MA, Tidwell AS, Hecht S. Radiographic diagnosis of lung lobe torsion. Vet Radiol Ultrasound 2005; 46:478484.

  • 2. Murphy KA, Brisson BA. Evaluation of lung lobe torsion in pugs: 7 cases (1991–2004) J Am Vet Med Assoc 2006; 228:8690.

  • 3. Neath PJ, Brockman DJ, King LG. Lung lobe torsion in dogs: 22 cases (1981–1999). J Am Vet Med Assoc 2000; 217:10411044.

  • 4. Seiler GA, Schwarz T, Vignoll M, et al. Computed tomographic features of lung lobe torsion. Vet Radiol Ultrasound 2008; 49:504508.

  • 5. Schultz RM, Peters J, Zwingenberger A. Radiography, computed tomography, and virtual bronchoscopy in 4 dogs and two cats with lung lobe torsion. J Small Anim Pract 2009; 50:360363.

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