Remus, a 6-year-old male castrated mixed breed dog presents with chronic sneezing and bilateral nasal discharge that now has blood. What are the top four differential diagnoses?

• A. Aspergillosis, chronic rhinitis, nasal neoplasia, tooth root abscess
• B. Nasal polyps, rhinitis, sinusitis, fungal infection
• C. Nasal neoplasia, cryptococcosis, aspergillosis, trauma
• D. Allergic rhinitis, bacterial rhinitis, nasal polyp, tooth abscess

Answer: (A)

When a dog has chronic sneezing with nasal discharge and now shows blood, the nasal cavity is being affected by processes that damage mucosa or create space-occupying lesions. The four most likely culprits are fungal infection of the nose, inflammatory or infectious rhinitis, nasal tumors, and dental disease that drains into the nasal passages.

Aspergillosis is a fungal infection that targets the nasal passages and can cause sneezing, nasal discharge, and epistaxis. It often affects middle‑aged dogs and can progress with destruction of the nasal turbinates, which you may see on imaging. Topical antifungal treatment or systemic therapy is often needed, and recognizing it early matters for prognosis.

Chronic rhinitis reflects long‑standing inflammation of the nasal mucosa, which can be inflammatory, inflammatory‑infectious, or secondary to irritants. It commonly presents with persistent sneezing and bilateral nasal discharge. Management focuses on eliminating triggers when possible and treating secondary infections or inflammation.

Nasal neoplasia is a major consideration in dogs with ongoing nasal discharge and episodes of epistaxis, especially as age increases. Tumors such as adenocarcinoma or other nasal masses can cause unilateral or bilateral discharge, sneezing, and facial changes. Imaging to identify a mass and biopsy to determine the type guide treatment, which may include radiation or surgery depending on the tumor.

Tooth root abscess represents dental disease where an infected tooth root drains into the nasal cavity, producing nasal discharge and sometimes epistaxis. Dental radiographs help detect this, and treatment involves dental extraction or other dental therapy to remove the source of infection.

These four cover the most common and clinically relevant causes of chronic nasal signs with bleeding in dogs, making them the top differential diagnoses to pursue first.