Good Morning and welcome to Just answer. I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
I am so sorry to hjear about Mitzi's condition. I know this is scary for you and poor little Mitzi.
This hacing cough is either due to heart disease, lung diseaase or kennel Cough that bthe older dogs are more prone to because their immuen systems are suppressed due to age. If Mitzi is eating well and acting normal, this may be the case which is often harmless for Mitzi.
This lesion that is seen on the xrays could be a number of conditions:
Scar tissue form a previous injury or illness'
Fungal infection such as valley Fever
Tumor or cancer.
In most cases, the next step is to do a tracheal wash to determine if this is a fungal or bacterial infection. Your vet also could run an Ultrasound with a biopsy if heart disease is ruled out.
The botXXXXX XXXXXne for Mitzi is that further diagnostics are required to know if this cough is serious requiring aggressive treatment or if this will require heart medications to get this under control.
Does that make sense to you?
Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please Reply so I can clarify for you
Sincerely, XXXXX XXXXX