History
A 12-year-old spayed female mixed-breed dog was evaluated because of a 1-week history of productive cough, lethargy, diminished appetite, and intermittent vomiting that did not respond to empirical antimicrobial treatment. The dog was housed indoors but was allowed to roam outside, where it had access to wooded areas. The dog was current on vaccinations and received regular heartworm, flea, and tick preventative. Radiography performed by the referring veterinarian revealed suspected thoracic and abdominal masses. The dog was referred to the veterinary teaching hospital on the same day.
Upon evaluation, the dog had signs of mild depression and was markedly weak in the hind limbs. The dog was febrile and tachypneic with a mildly increased respiratory effort. Decreased to absent lung sounds were noted on auscultation over the left lung field. Generalized peripheral lymphadenomegaly and organomegaly in the cranial aspect of the abdomen were noted on physical examination. A CBC revealed mature neutrophilic leukocytosis (15,060 segmented neutrophils/μL; reference range, 2,650 to 9,800 segmented neutrophils/μL) and monocytosis (1,320 cells/μL; reference range, 165 to 850 cells/μL). Serum biochemical analysis revealed hyperglobulinemia (5.5 g/dL; reference range, 1.9 to 3.5 g/dL), hypoalbuminemia (2.4 g/dL; reference range, 2.9 to 4.1 g/dL), and high alkaline phosphatase activity (370 U/L; reference range, 42 to 126 U/L). Proteinuria was present (urine protein-to-creatinine ratio, 2.7; reference range, < 0.5). Digital radiography of the thorax was performed (Figure 1).
Right (A) and left (B) lateral and ventrodorsal (C) radio-graphic views of the thorax of a 12-year-old female mixed-breed dog with a 1-month history of moist productive cough, lethargy, diminished appetite, and intermittent vomiting.
Citation: Journal of the American Veterinary Medical Association 240, 8; 10.2460/javma.240.8.945
Right (A) and left (B) lateral and ventrodorsal (C) radio-graphic views of the thorax of a 12-year-old female mixed-breed dog with a 1-month history of moist productive cough, lethargy, diminished appetite, and intermittent vomiting.
Citation: Journal of the American Veterinary Medical Association 240, 8; 10.2460/javma.240.8.945
Right (A) and left (B) lateral and ventrodorsal (C) radio-graphic views of the thorax of a 12-year-old female mixed-breed dog with a 1-month history of moist productive cough, lethargy, diminished appetite, and intermittent vomiting.
Citation: Journal of the American Veterinary Medical Association 240, 8; 10.2460/javma.240.8.945
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Diagnostic Imaging Findings and Interpretation
On the right lateral and ventrodorsal views, a homogenous soft tissue opacity is evident in the caudal segment of the left cranial lung lobe, with an associated mediastinal shift toward the left, indicating volume loss of the left lung; a lobar sign separating the abnormal left cranial lung lobe from the normally inflated left caudal lung lobe is also evident (Figure 2). Lack of similar abnormalities on the left lateral radio-graphic view is worth noting because this lesion would have been missed if only this lateral view had been obtained.
Same right lateral (A) and ventrodorsal (C) radiographic images as in Figure 1. Notice the focal, homogenous soft tissue opacity (asterisk) in the left cranial lung lobe and the associated lobar sign (arrowheads) between this lung lobe and the normally aerated left caudal lung lobe. Also, notice shifting of the cardiac silhouette toward the left, indicating volume loss in the left lung.
Citation: Journal of the American Veterinary Medical Association 240, 8; 10.2460/javma.240.8.945
Same right lateral (A) and ventrodorsal (C) radiographic images as in Figure 1. Notice the focal, homogenous soft tissue opacity (asterisk) in the left cranial lung lobe and the associated lobar sign (arrowheads) between this lung lobe and the normally aerated left caudal lung lobe. Also, notice shifting of the cardiac silhouette toward the left, indicating volume loss in the left lung.
Citation: Journal of the American Veterinary Medical Association 240, 8; 10.2460/javma.240.8.945
Same right lateral (A) and ventrodorsal (C) radiographic images as in Figure 1. Notice the focal, homogenous soft tissue opacity (asterisk) in the left cranial lung lobe and the associated lobar sign (arrowheads) between this lung lobe and the normally aerated left caudal lung lobe. Also, notice shifting of the cardiac silhouette toward the left, indicating volume loss in the left lung.
Citation: Journal of the American Veterinary Medical Association 240, 8; 10.2460/javma.240.8.945
Abdominal radiography was also repeated and revealed mild caudal displacement of the gastric axis secondary to mild hepatomegaly. Several radiolucent foci with moth-eaten appearance were visible in the proximal metaphysis and diaphysis of both femora. Hepatization (consolidated pulmonary parenchyma appearing similar in echotexture to hepatic parenchyma) of the left cranial lung lobe was noted on limited thoracic ultrasonography.
Although the thoracic radiographic findings alone do not exclude other differential diagnoses such as bacterial pneumonia, given the combination of the clinical history, physical examination findings, and radiographic findings of infiltration and atelectasis in the left cranial lung lobe, mild hepatomegaly, and lytic foci in the proximal aspects of both femurs, disseminated neoplasia (eg, lymphoma) and fungal infection were considered the primary differential diagnoses.
Comments
Ultrasound-guided fine-needle aspiration of the abnormal lung tissue was performed, revealing Blastomyces organisms and moderate pyogranulomatous inflammation. Results of a urine Blastomyces antigen enzyme immunoassay were also positive (67.5 U; reference range, < 1.0 U). Abdominal and femoral abnormalities were not investigated at this time because of severity of pulmonary disease and monetary constraints.
The typical appearance of canine pulmonary blastomycosis on thoracic radiographs has been described as a diffuse nodular to miliary interstitial pattern; however, recent reports1 indicate that blastomycosis can appear as alveolar, unstructured interstitial, or focal structured interstitial patterns (nodules or masses) or as combinations of these patterns. Therefore, pulmonary blastomycosis should remain a differential diagnosis when thoracic projections reveal pulmonary patterns other than the traditional nodular to miliary interstitial pattern, especially in endemic regions. Although not seen in this dog, tracheobronchial lymphadenomegaly can be seen with pulmonary blastomycosis, being radiographically apparent in approximately one-fourth of affected dogs.1
Infection with dimorphic Blastomyces dermatitidis, the etiologic agent of pulmonary blastomycosis, occurs via inhalation of aerosolized conidia (asexual spores) that transform from mycelial to yeast phase within the alveolar macrophages of the terminal airways when exposed to normal mammalian internal body temperature.1,2 Lymphatic and hematogenous dissemination results in secondary infections of the lymph nodes, eyes, bones, and skin.1 Blastomycosis is typically seen in young adult large-breed dogs; environmental factors such as proximity to water are associated with an increased risk of exposure.3 Development of clinical signs can be delayed by weeks to months and typically consists of dyspnea (potentially cyanosis), tachypnea, anorexia, fever, lethargy, weight loss, and cachexia.1
The patient received a loading dose of itraconazole (10 mg/kg [4.5 mg/lb], PO, q 24 h) for 3 consecutive days that was then reduced to a maintenance dose (5 mg/kg [2.3 mg/lb], PO, q 24 h). Antifungal treatment was to continue 1 month past clinical resolution as determined by radiographic signs and results of urine Blastomyces antigen enzyme immunoassays.
- 1.↑
Crews LJ, Feeney DA, Jessen CR, et al. Radiographic findings in dogs with pulmonary blastomycosis: 125 cases (1989–2006). J Am Vet Med Assoc 2008; 232:215–221.
- 2.
Chen T, Legendre AM, Bass C, et al. A case-control study of sporadic canine blastomycosis in Tennessee, USA. Med Mycol 2008; 46:843–852.
- 3.↑
Kerl ME. Update on canine and feline fungal diseases. Vet Clin North Am Small Anim Pract 2003; 33:721–747.
