8 year-old, MN, Cocker Spaniel

This case was presented in the Summer of 2020 at our Virtual IDEXX Diagnostic Imaging CE event.

If you’re a senior diagnostic imaging resident preparing to sit for your certifying exam, this event is for you! Follow this link to learn more about this year’s virtual event on Aug 6-8, 2021, and register to attend.

History: Presented for one day of coughing. Progressed to labored breathing.  No history of collapsing trachea.

Images: 3 radiographs were provided.

How did we grade this?

Diffuse narrowing of trachea2
Small volume of pleural effusion2
Wide cranial mediastinum in VD2
Coagulopathy due to rodenticide is primary diagnosis4

Discussion:

The appearance of this case is very typical for a relatively uncommon, though well documented (references below) disease process – tracheal obstruction due to tracheal mural hemorrhage, likely affecting the dorsal tracheal membrane specifically, from a coagulopathy from rodenticide ingestion. The appearance of the trachea could potentially be interpreted as visualization of tracheal collapse, though the length of tracheal luminal narrowing (evident as an increased opacity and very thin gas filled lumen) that we see unchanged in both lateral projections would not be seen with tracheal collapse from chondromalacia (while the trachea can collapse throughout it’s length from chondromalacia, it would be exceedingly rare to see that degree and length of collapse in two lateral images). Combine this finding with widening of the cranial mediastinum (which is likely from mediastinal hemorrhage), a small volume of pleural effusion (likely hemorrhage), and the acute onset of the clinical signs, these findings can be best summarized with a systemic disease process and is best explained with a coagulopathy. Other differentials, such as round cell neoplasia with lymphoma in the mediastinum and tracheal membrane, could potentially cause this appearance, but tracheal neoplasia, even lymphoma, is anectdotally more limited in length. Images from the references below display the preserved and similar appearance of this disease process seen in multiple patients.

References:

  1. Blocker TL, Roberts BK. Acute tracheal obstruction associated with anticoagulant rodenticide intoxication in a dog. Journal of Small Animal Practice. 1999;40:577–580.
  2. Lawson C, O’Brien M, McMichael M. Upper Airway Obstruction Secondary to Anticoagulant Rodenticide Toxicosis in Five Dogs. J Am Anim Hosp Assoc. Allen Press; 2017 Jul 1;53:236–241.
  3. Berry CR, Gallaway A, Thrall DE, Carlisle C. Thoracic Radiographic Features of Anticoagulant Rodenticide Toxicity in Fourteen Dogs. Veterinary Radiology & Ultrasound. 1993;34:391–396.
  4. Thomer AJ, Beer KAS. Anticoagulant rodenticide toxicosis causing tracheal collapse in 4 small breed dogs. Journal of Veterinary Emergency and Critical Care. 2018;28:573–578.

Photo by Ashley Anderson on Unsplash

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