History
An 11-year-old 5.2-kg (11.4-lb) spayed female Miniature Poodle was evaluated because of a 2-month history of weight loss and 3-week history of a cyclic fever of unknown origin. Prior treatment provided by the referring veterinarian included a 1-week course of amoxicillin, and at the time of examination at our facility, the dog was receiving amoxicillin-clavulanic acid and marbofloxacin for presumptive pneumonia, diagnosed by the referring veterinarian on the basis of findings from thoracic radiography. In addition, the dog had a history of chronic hepatitis that was being managed with a therapeutic diet,a orally administered prednisone, and a daily nutritional supplement for liver health. The dog primarily resided in Pennsylvania but also spent time in Arizona with the owner.
On initial referral examination at our facility, the dog was febrile (rectal temperature, 39.8°C [103.6°F]; reference range, 37.2° to 39.2°C [99.0° to 102.6°F]) and had mild tachypnea and dyspnea. On abdominal palpation, the dog had an enlarged liver, consistent with the previously diagnosed chronic hepatitis and treatment with prednisone. Thoracic radiography was performed (Figure 1).
Left and right lateral (A and B) and ventrodorsal (C) thoracic radiographic views of an 11-year-old 5.2-kg (11.4-lb) spayed female Miniature Poodle evaluated because of a 2-month history of weight loss and a 3-week history of a cyclic fever of unknown origin.
Citation: Journal of the American Veterinary Medical Association 255, 9; 10.2460/javma.255.9.1005
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Radiographic Findings and Interpretation
Thoracic radiography revealed a diffuse interstitial pattern with a peribronchial infiltrate in the dog's lungs (Figure 2). In addition, mild bilateral pleural effusion was evident with rounding and retraction of the lung margins, several thin pleural fissure lines, and soft tissue opacity in the pleural space silhouetting with the cardiac silhouette. In the left lateral radiographic image, more so than the right lateral radiographic image, a soft tissue opacity in the ventral aspect of the thorax from the level of the third sternebra caudally appeared like an ill-defined mass that elevated the cardiac silhouette dorsally (mass effect). Ventral to the cardiac silhouette, the soft tissue opacity was mildly mottled. On the ventrodorsal radiographic image, this soft tissue opacity largely conformed to the mediastinum, with widening of the cranioventral and caudoventral mediastinal boundaries and middle mediastinal widening that caused the impression of cardiac silhouette enlargement. In addition, rounding and irregularity of the hepatic margins were present.
Same images as in Figure 1. There is a diffuse interstitial pattern, and pleural effusion is evidenced by mild rounding and retraction of the lung lobes (black arrows; A and B), pleural fissure lines (black arrowheads; C), and soft tissue opacity silhouetting with the cardiac silhouette. Mediastinal involvement is suggested by widening of the cranioventral and caudoventral mediastinal boundaries (dashed lines; C), widening of the middle mediastinum, and mild mottling of the ventral thoracic soft tissue opacity (white asterisks; A and B) at the level of the cardiac silhouette. There is increased soft tissue opacity in the region of the tracheobronchial lymph nodes (black asterisks; A through C). Rounding and irregularity of the hepatic margins are present (white arrowheads; A and B).
Citation: Journal of the American Veterinary Medical Association 255, 9; 10.2460/javma.255.9.1005
On the basis of findings on the ventrodorsal radiographic image, in which the caudal thoracic opacity was centered on midline and silhouetted with the cardiac silhouette, an alveolar pattern or mass in the accessory lung lobe could have been considered; however, given the ventral location of the soft tissue opacity evident on the lateral radiographic images, the opacity was considered mediastinal in origin. Additionally, tracheobronchial lymph node enlargement was suspected, owing to increased soft tissue opacity between the mainstem bronchi noted on the ventrodorsal image and mild dorsal deviation of the trachea at the heart base noted on the lateral images. The rotated position of the dog in the left lateral and ventrodorsal radiographic images may have exaggerated the mass effect by the ventral soft tissue opacity and appearance of mediastinal widening, respectively; however, the appearance was not deemed solely artifactual because of the soft tissue opacity mottling evident on the lateral image and the severity of the widening, especially caudally, evident on the ventrodorsal image.
Differential diagnoses included mediastinitis, pleuritis, pneumonia, and lymphadenopathy from infectious causes (eg, fungal or bacterial) or, less likely, foreign body migration. Neoplasia (eg, mesothelioma or carcinomatosis) was considered much less likely. Sternal or cranial mediastinal lymphadenopathy, alone or in combination, was considered a contributing factor to the cranial mediastinal widening noted radiographically. In addition, a component of the pulmonary interstitial pattern could have been from mild pulmonary collapse secondary to the presence of pleural effusion and mediastinal enlargement. The abnormal radiographic appearance of the hepatic margins was considered consistent with the previously diagnosed chronic hepatitis and with steroid hepatopathy.
Thoracic ultrasonography was performed to guide lesion sampling and to evaluate the pleural space and ventral aspect of the mediastinum. Ultrasonography confirmed bilateral pleural effusion, ventral mediastinal thickening with soft tissue-like echogenicity (Figure 3), and sternal lymphadenopathy (not shown). Ultrasonographically guided thoracocentesis and fine-needle aspiration of the thickened mediastinal tissue and enlarged sternal lymph node were performed. Cytologic evaluation revealed that all samples (fluid and tissue) contained fungal organisms consistent with Coccidioides immitis, and the cytologic diagnosis was exudative effusion with pyogranulomatous inflammation in the mediastinal tissues and lymph nodes.
Ultrasonographic image of the caudoventral aspect of the thorax of the dog in Figures 1 and 2 in a longitudinal plane. A mildly heterogeneous mass-like structure (arrows) surrounded by pleural effusion (asterisks) is present, consistent with thickening of the caudoventral mediastinal tissues or a mediastinal granuloma, alone or in combination.
Citation: Journal of the American Veterinary Medical Association 255, 9; 10.2460/javma.255.9.1005
Treatment and Outcome
The dog was discharged with a prescription of itraconazole (4.8 mg/kg [2.2 mg/lb], PO, q 24 h, for 2 weeks) for treatment of coccidioidomycosis, and the dosage of prednisone was decreased to 0.24 mg/kg (0.1 mg/lb), PO, every other day. The dog was returned for a recheck examination 2 weeks later, and results of physical and radiographic examinations indicated disease progression despite treatment. The owners declined further treatment and took the dog home for palliative care and eventual euthanasia. A necropsy was not performed.
Comments
Coccidioidomycosis, caused by C immitis, is a fungal disease that primarily affects the lungs after inhalation of infective arthrospores but does occasionally become disseminated.1 The disseminated form can be found in the lungs, regional lymph nodes, bone, CNS, or parenchymal organs, alone or in combination.2 Coccidioidomycosis is endemic to areas of the southwestern United States, such as Arizona.1 The most common clinical sign is a chronic cough, with less common additional sequelae including anorexia, lethargy, and pyrexia.1 Diagnosis of coccidioidomycosis can be a multifaceted process, including history of travel or residence in C immitis-endemic areas combined with findings from physical examination, diagnostic imaging, and cytologic, histologic, and serologic evaluations.1 The prognosis for animals with coccidioidomycosis varies and depends on the severity of the disease and degree of systemic involvement.1 Treatment includes administration of an azole product (eg, itraconazole as used in the dog of the present report) or amphotericin B; however, no approach is considered to be the gold standard, and prevention of exposure to infective arthrospores is best.1
No thoracic radiographic finding is pathognomonic for coccidioidomycosis; however, there are abnormalities that are strongly suggestive of the disease.1 For instance, tracheobronchial (hilar) lymphadenopathy has been found in 50% to 75% of affected dogs, with cranial mediastinal lymphadenopathy less common unless the lymph nodes are markedly enlarged.1–3 The most common pulmonary abnormality evident radiographically is an ill-defined diffuse interstitial pattern; however, pulmonary nodules, patchy alveolar infiltrates, and peribronchial infiltrates, alone or in combination, may also be evident.1–3 Pleural effusion or pleural thickening is a less common radiographic finding, seen in 18 of 38 (47%) dogs in 1 study,2 and mediastinitis is a much less well-described sequela of this disease.4 The dog of the present report had radiographic findings that were common (mixed lung pattern and lymphadenopathy) and less common (pleural effusion and mediastinitis).
The use of ultrasonography in the dog of the present report was beneficial in confirming tissue thickening in the mediastinum as suspected on the basis of radiographic findings. Similarly, a study5 shows that ultrasonography is beneficial in distinguishing pleural effusion from solid pleural or mediastinal tissue in dogs with chronic pyogranulomatous pleural disease. However, we could not determine with ultrasonography whether the ventral mediastinal thickening represented fungal granulomas in the mediastinum, mass-like proliferation of the mediastinal pleural tissues associated with pyogranulomatous medias-tinitis,4–6 or both. Computed tomography is better than ultrasonography and radiography for evaluating pleural space disease, including mediastinitis,5,6 and could have been useful in evaluating the full extent of the thoracic abnormalities in the dog of the present report. Nonetheless, radiography and ultrasonography combined were useful in identifying pleural effusion and ventral mediastinal thickening or masses surrounded by pleural effusion, suggestive of mediastinitis. These findings combined with the dog's clinical signs and history suggested an infectious condition, particularly coccidioidomycosis because the dog spent time in Arizona. Cytologic evidence of fungal organisms consistent with C immitis in all thoracic samples further supported a diagnosis of coccidioidomycosis.
Footnotes
Prescription Diet l/d Canine, Hill's Pet Nutrition Inc, Topeka, Kan.
References
1. Graupmann-Kuzma A, Valentine BA, Shubitz LF, et al. Coccidioidomycosis in dogs and cats: a review. J Am Anim Hosp Assoc 2008;44:226–235.
2. Millman TM, O'Brien TR, Suter PF, et al. Coccidioidomycosis in the dog: its radiographic diagnosis. Vet Radiol Ultrasound 1979;20:50–65.
3. Johnson LR, Herrgesell EJ, Davidson AP, et al. Clinical, clinicopathologic and radiographic findings in dogs with coccidioidomycosis: 24 cases (1995–2000). J Am Vet Med Assoc 2003;222:461–466.
4. Wisner ER, Zwingenberger AL. Mediastinum and esophagus. In: Wisner ER, Zwingenberger AL, eds. Atlas of small animal CT and MRI. Ames, Iowa: John Wiley and Sons Inc, 2015;408–422.
5. Trinterud T, Nelissen P, Caine AR, et al. Mediastinectomy for management of chronic pyogranulomatous pleural disease in dogs. Vet Rec 2014;174:607.
6. Swinbourne F, Baines EA, Baines SJ, et al. Computed tomographic findings in canine pyothorax and correlation with findings at exploratory thoracotomy. J Small Anim Pract 2011;52:203–208.
