Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

THE RESPIRATORY SYSTEM • 327
change in voice, and loss of bark. A characteristic stridor may be heard when
the dog inhales. Sudden death can occur from respiratory obstruction.
Tracheal tumors are rare. In older dogs they tend to be malignant
(osteosarcomas). In young dogs they are more likely to be benign (osteochondromas).
The most common sign is a productive cough. Stridor on inhalation
may be noted during exercise or panting. Cyanosis and collapse can occur
when the tumors get very large and cause severe respiratory obstruction.
Lung tumors account for about 1 percent of all neoplasms in dogs. Most
arise from cells lining the bronchi. They tend to occur in older dogs of both
sexes. Lung tumors in dogs may be associated with exposure to cigarette
smoke.
Most primary lung tumors are malignant and will have already spread to
other parts of the body by the time they are diagnosed.
A harsh, nonproductive cough is the most common sign. Pleural effusion
may occur as a late complication.
Metastatic lung tumors—that is, tumors that spread to the lungs from
other parts of the body—are more common than primary lung tumors. Tumors
that metastasize to the lungs include mammary gland cancers, osteosarcomas,
thyroid cancers, melanomas, and squamous cell carcinomas.
Treatment: Surgical exploration and removal of small tumors offers the
best chance for cure. Larger tumors usually cannot be cured, but may respond
to chemotherapy. The advanced age of many dogs with respiratory tract
tumors usually makes aggressive treatment impractical.