What Is Your Diagnosis?

Steven L. Tsai Foster Hospital for Small Animals, Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.

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Amy F. Sato Foster Hospital for Small Animals, Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.

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History

A 4-month-old sexually intact male Golden Retriever was brought to the emergency room in fulminant respiratory distress. Earlier in the day, the dog had swallowed a fish hook, which it subsequently vomited. Because of the dog's extreme dyspnea, only a single lateral radiographic view of the thorax was obtained (Figure 1).

Figure 1—
Figure 1—

Lateral radiographic view of the thorax of a 4-month-old male Golden Retriever in acute respiratory distress.

Citation: Journal of the American Veterinary Medical Association 232, 7; 10.2460/javma.232.7.995

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

Radiographic Findings and Interpretation

A well demarcated regional alveolar pattern is evident in the caudodorsal lung fields, characterized by greater than normal pulmonary parenchymal opacity with loss of visibility of the pulmonary vascular margins and presence of air bronchograms (Figure 2). A well defined, rounded soft tissue opacity occludes the lumen of the cervical portion of the trachea. A small amount of gas is in the cervical portion of the esophagus. The cardiac silhouette and visible pulmonary vasculature were considered within normal limits. The primary diagnosis was noncardiogenic pulmonary edema secondary to upper airway obstruction.

Figure 2—
Figure 2—

Same radiographic view as in Figure 1. Areas of interest are shown. A—Kibble in trachea (arrows). Notice gas in cervical portion of the esophagus. B—Notice the alveolar pattern in the caudodorsal lung fields.

Citation: Journal of the American Veterinary Medical Association 232, 7; 10.2460/javma.232.7.995

Comments

Causes of noncardiogenic pulmonary edema include upper airway obstruction, volume overload, smoke or other toxin inhalation, sepsis, thoracic or cranial trauma, seizures, and electrocution.1,2 Noncardiogenic pulmonary edema usually results from increased permeability of the pulmonary capillary membranes, although increased pulmonary venous hydrostatic pressure may also be an important cause.3

Noncardiogenic pulmonary edema caused by upper airway obstruction is classified as negative pressure pulmonary edema (NPPE).4 The pathogenesis is unclear; however, major contributors to the development of NPPE are believed to be substantial intrathoracic negative pressure, hypoxia, and a hyperadrenergic state.4,5 These factors combine to increase venous return to the right side of the heart and pulmonary vascular resistance, thereby increasing transmural pressure across the alveolar-capillary membranes.4 Hypoxia and the hyperadrenergic state may also have direct effects on the integrity of the capillary membranes.5

Age and breed associations have been reported for various causes of airway obstruction. Younger dogs are more likely to develop signs secondary to strangulation (from pulling on neck leads).1 Older dogs more commonly develop airway obstruction as a result of laryngeal paralysis or masses.1,3 Bulldogs, which are likely to have airway obstruction secondary to brachycephalic syndrome, are overrepresented.1

The most common radiographic finding in NPPE (and other noncardiogenic pulmonary edemas) is an alveolar or mixed interstitial-alveolar pattern of pulmonary infiltrates.1,3 Abnormalities are predominantly seen in the caudodorsal and perihilar lung fields, with other lung fields variably involved.1,3 Asymmetry may be evident, with the right lung lobes more commonly affected to a greater degree.1,3 Animals with NPPE have more severe radiographic changes than animals with pulmonary edema caused by cranial trauma, seizures, or electric shock.1 Animals with peracute onset of clinical signs typically have more severe radiographic abnormalities.3 Cardiac structures are within normal limits unless the animal has unrelated cardiac disease.6 Negative pressure pulmonary edema is a dynamic process, often with partial or complete resolution of radiographic evidence of edema within 2 days after treatment.3

Although a ventrodorsal radiographic view of the thorax would have been optimal to further evaluate the severity and distribution of pulmonary edema, respiratory distress in the dog of this report precluded a thorough workup. When clinically feasible, an orthogonal radiographic view is recommended to rule out the possibility of external foreign material giving the false impression of a tracheal foreign body and to provide a complete baseline study for assessing resolution of pulmonary changes via follow-up radiographic examinations.

Immediate administration of supplemental oxygen did not result in clinical improvement of the dog of this report. A temporary tracheostomy tube was inserted after the dog was anesthetized. Endoscopic examination revealed a piece of kibble lodged in the trachea caudal to the arytenoid cartilages. The kibble was removed by advancing an endotracheal tube cranially from the tracheostomy site. Oxygen supplementation was continued for 2 days before the dog was discharged. Thoracic radiography performed 2, 5, and 13 days following admission revealed progressive resolution of pulmonary abnormalities.

  • 1.

    Drobatz KJ, Saunders HM, Pugh CR, et al. Noncardiogenic pulmonary edema in dogs and cats: 26 cases (1987–1993). J Am Vet Med Assoc 1995;206:17321736.

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  • 2.

    Suter PF, Lord PF. Lower airway and pulmonary parenchymal diseases. In: Suter PF, Lord PF, eds. Thoracic radiography: a text atlas of thoracic diseases of the dog and cat. Wettswil, Switzerland: PF Suter, 1984;553568.

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  • 3.

    Kerr LY. Pulmonary edema secondary to upper airway obstruction in the dog: a review of nine cases. J Am Anim Hosp Assoc 1989;25:207212.

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  • 4.

    Louis PJ, Fernandes R. Negative pressure pulmonary edema. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;93:46.

  • 5.

    Lang SA, Duncan PG, Shephard DA, et al. Pulmonary oedema associated with airway obstruction. Can J Anaesth 1990;37:210218.

  • 6.

    Drobatz KJ, Concannon K. Noncardiogenic pulmonary edema. Compend Contin Educ Pract Vet 1994;16:333345.

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