Hello, my name is***** and I have over 20 years of experience as a veterinarian. I understand that you are concerned about Zuko's chronic nasal congestion, sneezes and reverse sneezes, and pawing at his nose and I'd like to help.
Is the discharge from both sides of the nose?
What color is his nasal discharge now, has it ever been different?
Sneezing and reverse sneezing are signs of nasal and pharyngeal irritation.
With nasal irritation we can also see a nasal discharge which can be yellow, white, green, mucoid or even bloody in character. In some cases with long term infections or a mass we can even see bleeding and nasal bone destruction and swelling or changes in nose conformation or around the eye.
Possible reasons for these symptoms are bacterial, fungal, or viral infections, nasal mites, a foreign body in the nose, a polyp or mass in the nose or a tooth root infection.
Another possibility is a sterile inflammatory condition called lymphoplasmacytic rhinitis, although this is more common in cats. This disease process is a chronic inflammation and thickening of the nasal mucosa that does not cause any changes in the nasal bones, and is not associated with any sort of infection. It is steroid responsive, but high doses of steroids for long periods of time can be rough on his gastrointestinal tract, liver and kidneys and can cause diabetes. Ideally we get the condition under control with a high dose of steroids and then slowly reduce the dose to the lowest possible to control the condition. Some dogs can come off steroids completely for long periods of time without symptoms returning, but most need steroids chronically at lower levels.
Because we need to use immunosuppressive with this disease we want to make sure we look for infectious causes first and rule them out, and biopsies for a definitive diagnosis is ideal.
Allergies are rarely the cause of chronic nasal congestion, dogs seem to get itchy with allergies, not nasal congestion.
It is tough to know whether he responded to the steroids or antibiotics because both were used. I would have expected him to improve with a foreign body, polyp, mass, or tooth root infection, nasal mites or lymphoplasmacytic rhinitis with these medications.
Diagnosis of a the problem behind these symptoms can be complicated. We may need to perform radiographs of the nose and sinuses looking for changes in the bones or full sinuses, nasal flushes and scoping to collect culture and biopsy specimens and sometimes blood titers to look for the infection (especially if we are suspicious of a fungal infection).
To check general health I would start with a complete blood count and biochemistry profile and thyroid profile.
If those tests come back normal then looking for a tooth root infection, a foreign body or polyp with a nasal scope and radiographs of his tooth roots, nose and sinuses under sedation would be recommended. A biopsy of any abnormal tissue could be diagnostic.
I would also check for a fungal infection by checking blood titers for fungal infections found in your area, aspergillosis tends to cause nasal congestion and infections throughout the US.
I would be less concerned about a tumor in a young dog. I understand that money is tight. If you decide that you cannot or would not run any further diagnostics, and his physical examination is relatively normal then trying an antibiotic alone such as Clindamycin, Doxycycline or Clavamox for a longer period of time, until the discharge clears and then another week, could be an option. These antibiotics are good for treating tooth and respiratory tract infections.
You can also choose to have testing done in a stepwise fashion if he's not improving.
Best of luck with your fellow, please let me know if you have any further questions.