What Is Your Diagnosis?

Kelly M. Makielski Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011.

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Nina R. Kieves Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011.

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Lindsey J. Gilmour Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011.

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Krysta L. Deitz Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011.

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History

An 8-year-old 3.75-kg (8.25-lb) spayed female domestic shorthair cat was referred for evaluation because of a suspected pulmonary mass observed on whole body radiographs. The patient was initially evaluated by the referring veterinarian because of weight loss of 2 months’ duration. No abnormalities were found on hematologic evaluation, serum biochemical analysis, or urinalysis. Serologic results of FeLV antibody and FIV antigen testing were negative.

On referral physical examination, the patient was quiet and alert and had a body condition score of 2 of 9 with generalized muscle wasting. Mild tachypnea was evident (respiratory rate, 62 breaths/min). The respiratory character was shallow, but no abdominal effort was observed. Decreased lung sounds were detected on auscultation of the left hemithorax. No abnormalities were detected on abdominal palpation. Radiographs of the thorax were obtained (Figure 1).

Figure 1—
Figure 1—

Right lateral (A) and dorsoventral (B) radiographic views of an 8-year-old spayed female domestic shorthair cat evaluated because of weight loss of 2 months’ duration.

Citation: Journal of the American Veterinary Medical Association 246, 1; 10.2460/javma.246.1.55

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

Radiographic Findings and Interpretation

A large volume of free gas is evident within the left pleural space, creating a lateral convexity of the left thoracic wall on the dorsoventral image (Figure 2). Pulmonary vasculature is radiographically absent throughout most of the left hemithorax. A marked midline shift of the cardiac silhouette, with trachea and mainstem bronchi toward the right side, is evident. Tenting of the eighth through tenth left intercostal muscles is present, along with a caudal convexity of the left diaphragmatic crus. On the right lateral image, the heart appears slightly separated from the sternum. A triangular-shaped, heterogeneous soft tissue opacity containing gas lucencies is present in the cranial portion of the thorax that spans the fourth through seventh intercostal spaces on the dorsoventral projection, consistent with an atelectatic lung lobe. A second diamond-shaped soft tissue mass is present in the left caudal portion of the thorax on the dorsoventral projection from the tenth through the eleventh intercostal space. Additionally, a small soft tissue opacity is located at the level of the eighth intercostal space on the right lateral image.

Figure 2—
Figure 2—

Same radiographic images as in Figure 1. Mild separation of the heart from the sternum is present on the right lateral image. Two soft tissue or fluid opacities (arrows) are visualized: a triangular-shaped opacity in the cranial portion of the thorax and a diamond-shaped opacity in the caudal portion of the thorax. A small soft tissue opacity is present at the eighth intercostal space (arrowhead). On the dorsoventral view, a marked midline shift of the cardiac silhouette and a large volume of free gas within the left pleural space (asterisk) are evident. Lateral convexity of the left thoracic wall and tenting of the caudal intercostal muscles are the results of severe tension pneumothorax.

Citation: Journal of the American Veterinary Medical Association 246, 1; 10.2460/javma.246.1.55

The radiographic diagnosis is severe, left-sided tension pneumothorax. The marked midline shift of the cardiac silhouette and tenting of the intercostal muscles are evidence of increased intrathoracic pressure in the left hemithorax. On the basis of the diamond shape and soft tissue opacity of the caudal soft tissue structure within the left thorax, a mass in the left caudal lung lobe was suspected. The primary differential diagnosis for this patient was spontaneous tension pneumothorax secondary to pulmonary neoplasia. Other potential differential diagnoses for the suspected left caudal pulmonary mass included granuloma or abscess. The soft tissue nodule increases the suspicion of a neoplastic process.

Treatment and Outcome

The cat of the present report was suspected to have a spontaneous tension pneumothorax secondary to pulmonary neoplasia. Tension pneumothorax is generally a life-threatening condition; however, this cat was relatively stable.

Thoracocentesis was not performed as the patient soon underwent bilateral thoracoscopy. At surgery, multiple round, raised, tan to white nodules were observed along the pleura, mediastinum, and surface of the left cranial and caudal lung lobes. The left cranial lung lobe had areas of dark red to brown discoloration. No discrete masses were observed within any of the lung lobes. Adhesions were observed between the pulmonary parenchyma and the pleura; however, all lung lobes were viewed. The left lobes appeared atelectatic with irregular margins, and no nodules were observed within the pulmonary parenchyma on palpation. The right lobes appeared grossly normal and inflated. Numerous biopsy specimens were taken, and a thoracostomy tube was placed. Recovery from surgery was uneventful.

Histologic findings confirmed the presence of a metastatic carcinoma of unknown tissue origin. Further diagnostic tests were declined by the owner, and the patient was euthanized 3 weeks following initial evaluation.

Comments

Pneumothorax is defined as free air within the pleural space and can be either traumatic or spontaneous.1 Traumatic pneumothorax occurs secondary to injury to the thoracic wall or airways. Spontaneous pneumothorax occurs in the absence of trauma and can be either primary or secondary.1 Primary spontaneous pneumothorax is common in dogs and occurs secondary to rupture of pulmonary bullae. Secondary spontaneous pneumothorax occurs as a result of pulmonary parenchymal or airway disease causing air leakage.

Reported causes of secondary spontaneous pneumothorax in cats include inflammatory airway disease, heartworm infection, neoplasia, pulmonary abscess, and lungworm infection.2 Neoplasia was documented in 42% of cases with underlying disease in the largest retrospective study2 of cats with spontaneous pneumothorax. Spontaneous pneumothorax resulting from bullae rupture has uncommonly been reported in cats secondary to suspected bronchopulmonary dysplasia.3 A potentially life-threatening manifestation of pneumothorax is a tension pneumothorax. This occurs as a result of progressive air accumulation within the pleural space, typically caused by continuous air leakage from damaged lung parenchyma.1 This progressive air accumulation leads to increased intrathoracic pressure, atelectasis, and increased mechanical pressure on intrathoracic structures.

Clinical signs of pneumothorax in cats and dogs include respiratory distress, tachypnea, lethargy, decreased appetite, and hiding behavior.1,2 Physical examination findings generally include tachypnea and absent lung sounds.1,2 Diagnosis is made by findings on thoracic radiography; however, repeated radiography following thoracocentesis, CT, hematologic analysis, and histologic evaluation may all be indicated to determine the underlying cause. Treatment of spontaneous secondary pneumothorax can include intermittent percutaneous thoracocentesis, surgical intervention, and thoracostomy tube placement.1,2 Prognosis is variable depending on the underlying etiology but should be considered guarded, with only 54% of cats surviving to discharge in 1 study.2

  • 1. Pawloski DR, Broaddus KD. Pneumothorax: a review. J Am Anim Hosp Assoc 2010; 46:385397.

  • 2. Mooney ET, Rozanski EA, King RG, et al. Spontaneous pneumothorax in 35 cats (2001–2010). J Feline Med Surg 2012; 14:384391.

  • 3. Milne ME, McCowan C, Landon BP. Spontaneous pneumothorax caused by ruptured pulmonary bullae associated with possible bronchopulmonary dysplasia. J Am Anim Hosp Assoc 2010; 46:138142.

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  • Figure 1—

    Right lateral (A) and dorsoventral (B) radiographic views of an 8-year-old spayed female domestic shorthair cat evaluated because of weight loss of 2 months’ duration.

  • Figure 2—

    Same radiographic images as in Figure 1. Mild separation of the heart from the sternum is present on the right lateral image. Two soft tissue or fluid opacities (arrows) are visualized: a triangular-shaped opacity in the cranial portion of the thorax and a diamond-shaped opacity in the caudal portion of the thorax. A small soft tissue opacity is present at the eighth intercostal space (arrowhead). On the dorsoventral view, a marked midline shift of the cardiac silhouette and a large volume of free gas within the left pleural space (asterisk) are evident. Lateral convexity of the left thoracic wall and tenting of the caudal intercostal muscles are the results of severe tension pneumothorax.

  • 1. Pawloski DR, Broaddus KD. Pneumothorax: a review. J Am Anim Hosp Assoc 2010; 46:385397.

  • 2. Mooney ET, Rozanski EA, King RG, et al. Spontaneous pneumothorax in 35 cats (2001–2010). J Feline Med Surg 2012; 14:384391.

  • 3. Milne ME, McCowan C, Landon BP. Spontaneous pneumothorax caused by ruptured pulmonary bullae associated with possible bronchopulmonary dysplasia. J Am Anim Hosp Assoc 2010; 46:138142.

    • Crossref
    • Search Google Scholar
    • Export Citation

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