Transtracheal wash (TTW) may also be known by the name bronchial lavage. Both are diagnostic tests performed to diagnose a respiratory tract problem, most commonly a chronic and/or recurring cough.
Before moving on, let’s define some terms. The trachea, or windpipe, is the large tube that carries air breathed in through the mouth or nose, down into the deeper airway structures. Bronchi are the tubes making up the first branches of the trachea. They then branch into smaller tubes called bronchioles, which then lead to the sacs that actually perform gas exchange, called alveoli.
TTW is performed under light general anesthesia. A tube is passed into the deepest part of the trachea, or a little further if a bronchial sample is desired. Sterile fluid is injected with a syringe, then pulled right back out. From the resulting specimen two tests are performed.
One is called bacterial culture and sensitivity. Because many patients with chronic cough have infection with resistant bacterial organisms, this test can help us identify the problem organism(s) as well as determine the best antibiotic treatment to kill that organism.
The remaining specimen is submitted to a pathologist for cytology. The doctor of pathology will stain the material, then look at it under a microscope. From there he can see what response the body is producing, infectious organisms, cells from the lining of the trachea and/or bronchi, as well as other structures.
“Other structures” may include tumor cells (cancerous or non-cancerous), parasites and the eggs of parasites. A common parasite of dog and cat lungs is Capillaria aerophila.
Patient cells from the lavage can be extremely valuable, as many chronic cough patients suffer from hypersensitivity problems, in which the immune system overreacts to irritants such as dust, pollen or mold, causing a harsh, hacking cough. Of course, if such patients are treated for infection, and there is none, they are unlikely to improve.
Conversely, patients with chronic infection who are treated for hypersensitivity are equally unlikely to improve.
Bronchial lavage is a valuable test that can improve the lives of dogs and cats with respiratory tract complications.
See you tomorrow, Dr. Randolph.