Coughing dog

This is "Toby", a 10 year old male Welsh Corgi.

Past history says that he was diagnosed with Dirofilariasis at 5 years of age, and was treated with a course of an arsenical adulticide. He has since been on a monthly microfilaricide. He has been well until one month ago, when he began coughing. It is a non-productive cough, occurring several times a day. Nothing unusual is detected on auscultation.

Q.1) Chest radiographs were taken: read them carefully: is there any evidence of the former heartworm disease?

Q.2) What other tests do you suggest now?

A full blood profile was obtained: it was non-contributary.

Toby was taken to surgery (See the discussion for what was done). He recovered well, and follow up examinations (including radiographs) over the next year were normal. However, at 18 months after surgery, he began coughing and gagging. Symptomatic treatment (Rikodeine [dihydrocodeine]cough syrup) did not resolve the problem. There was also a wheezing inspiratory noise. This time, radiographs of the chest and the cervical trachea were taken.

Q.3) Read the new radiographs.

Q.4) What do you suggest be done now?




Q.1) The radiographs show no appreciable evidence of the former dirofilariasis. Vertebral heart score is 10.0. The films show a well-circumscribed soft tissue lesion in the cranial thorax, ventral to the trachea and on the left side: there is no cardiac or tracheal displacement. The most likely location is in the cranial part of the left cranial lung lobe. A less likely alternative would be a ventral mediastinal mass, such as enlargement of the suprasternal lymph nodes, but these typically merge more diffusely with the sternal border.

Q.2) Appropriate investigation would be ultrasound examination of the mass, from the left cranioventral thorax. With U/S, it was found to have a reasonably distinct margin, and a somewhat heterogeneous soft tissue structure, with no fluid cavities. U/S guided FNA of the mass would also be useful: in this case, a diagnosis of bronchogenic carcinoma was made.
Toby was taken to surgery, and the affected lobe was excised. The diagnosis was confirmed histologically, and a guarded to poor prognosis was given, due to evidence of lymphatic invasion.  Post-operative chemotherapy and/or radiation therapy was considered, but was excluded on the basis of costs and dubious efficacy.

Q.3) The new radiographs show nothing of concern in the thorax, but reveal a soft tissue mass in the tracheal lumen, apparently originating from the dorsal tracheal wall, from a rather broad base.  Tracheal wall neoplasia and (less likely) foreign body or granuloma were thought likely.

Q.4)  Endoscopic evaluation and FNA were recommended (care with tracheal bleeding!). The diagnosis from the FNA was squamous cell carcinoma, originating from the dorsolateral tracheal wall. Given that the tumour appeared to extend for about 4 tracheal rings, excision and end-to-end anastimosis were offered (excision of up to 6 tracheal rings is usually acceptable). The client declined further surgical intervention.

This case comes from the files of the University of Melbourne Veterinary Clinic & Hospital, and was prepared for your enjoyment by Russell Mitten.




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