History: One day history of coughing, progressed to labored breathing. No prior medical problems.
Questions to ask yourself:
- Does the lack of prior medical problems affect the differentials?
- Can the tracheal collapse be related to the pleural and mediastinal effusion?
- What specific tests should be run and what history can be asked?
- What Radiation Safety Violation was committed during this study?
FINDINGS: The cardiac silhouette is normal in size and shape. The pulmonary vessels are narrowed. There is severe, diffuse narrowing of the trachea. A small volume of pleural fluid is present, causing retraction of the ventral lungs, increased soft tissue opacity in the ventral thorax, and small pleural fissure lines. The lungs are incompletely expanded, resulting in a mild diffuse interstitial lung pattern. No focal pulmonary parenchymal abnormalities are identified. The cranial mediastinum is wide on the ventrodorsal view. No abnormalities are detected in the limited view of the abdomen. No skeletal abnormalities are identified.
CONCLUSIONS: The diffuse narrowing of the trachea is of uncertain cause. Although rare, there are cases of hemorrhage within the dorsal tracheal membrane secondary to a coagulopathy, which could also explain the small volume of pleural fluid (i.e hemothorax). Other causes of a narrowed trachea including severe infectious tracheitis or dynamic tracheal collapse are not excluded. Additionally, other causes of pleural fluid including vasculitis, hypoproteinemia, chylothorax or malignant effusion are not ruled out. The wide mediastinum could also be the result of hemorrhage. The narrowed pulmonary vessels are suggestive of dehydration/hypovolemia.
RECOMMENDATIONS: A platelet count and coagulation panel are recommended. If a coagulopathy is not present, ultrasound-guided thoracocentesis may be considered. Additionally, airway sampling via tracheoscopy may be beneficial for cytology and culture/sensitivity. Depending on the results of those exams, fluoroscopic evaluation of the trachea may be considered to assess for any evidence of dynamic tracheal collapse.
Follow up: A coagulopathy was confirmed and the patient did indeed have exposure to rodenticide. He is doing well with treatment.
References:Berry CR et al. “Thoracic radiographic features of anticoagulant rodenticide toxicity in fourteen dogs.” Veterinary Radiology & Ultrasound 34.6 (1993): 391-396.
Blocker TL and Roberts BK. “Acute tracheal obstruction associated with anticoagulant rodenticide intoxication in a dog.” J Small Animal Practice 40.12 (1999): 577-580.
Lawson C, O’Brien M, and McMichael M. “Upper Airway Obstruction Secondary to Anticoagulant Rodenticide Toxicosis in Five Dogs.” J American Animal Hospital Association 53.4 (2017): 236-241.
Pardali DS et al. “Acute tracheal narrowing presumptively associated with anticoagulant rodenticide intoxication in a dog.” J Hellenic Veterinary Medical Society 62.3 (2011): 235-239.
Thomer AJ and Santoro KB. “Anticoagulant rodenticide toxicosis causing tracheal collapse in 4 small breed dogs”. J Veterinary Emergency and Critical Care (2018): 28(6), 573-578.