Vet’s 2025 Guide to Interstitial Pneumonia in Dogs 🐾 When the Tissue Between the Alveoli Gets Flamed🩺

By Dr. Duncan Houston BVSc

💡 Introduction

Interstitial pneumonia refers to inflammation in the walls (interstitium) of alveoli—the tiny air sacs in the lungs—rather than infections in larger airways or pleural cavities. The resulting stiff, fibrotic lung reduces oxygen exchange, causing exercise intolerance, cough, and respiratory distress.

1. What Is Interstitial Pneumonia? 🐾

Unlike bronchial or alveolar pneumonia, interstitial pneumonia primarily affects the alveolar walls and capillaries. The lung becomes less compliant and shows a diffuse radiographic pattern.

• Idiopathic pulmonary fibrosis: common in breeds like West Highland White Terriers and Bull Terriers; lungs stiffen over months.
• Pneumocystis pneumonia: seen in immunocompromised dogs like CKCS; a fungal-like parasite target the alveolar walls.

2. Which Dogs Are Affected?

• Middle-aged to older dogs—especially Westies, Bull Terriers, Cairn Terriers, Jack Russells and Dachshunds.
• Immunocompromised or steroid-treated dogs may be predisposed to Pneumocystis infections.
• Exposure to lung irritants—dust, smoke, chemicals—can trigger interstitial inflammation.

3. Clinical Signs & Onset ⚠️

• Gradual onset of exercise intolerance, rapid breathing (tachypnea), and cough.
• Sometimes fever, weight loss, or respiratory distress, depending on the disease stage.
• Physical exam may reveal “Velcro crackles”—fine end-inspiratory sounds—especially over lung fields.

4. Causes & Risk Factors

• Idiopathic fibrosis: progressive scarring without an identifiable trigger, common in terriers.
• Pneumocystis carinii infection: causes cystic and interstitial changes, often in younger CKCS or immunosuppressed dogs.
• Toxic/occupational exposures: smoke, chemical fumes, dust; sometimes secondary to lung injury from viral infections like distemper.
• Uremic or metastatic lung damage: secondary to kidney disease or cancer.

5. Diagnosis in 2025 🧪

5.1 Imaging

• Thoracic X-rays: diffuse interstitial to alveolar patterns—reticular, nodular, or mixed—diffuse lung opacity. (Radiographs showcased above.)
• Ultrasound (Lung‑BLUE): presence of vertical B/C-lines and pleural irregularities—early signs of interstitial disease.

5.2 Advanced Diagnostics

• CT scan: high-resolution images detect early fibrosis and differentiate from other diseases.
• Bronchoscopy and BAL: especially for suspected Pneumocystis—cytology confirms organisms.
• Open‑lung biopsy: rare but definitive; reserved for unclear or complex cases.

6. Treatment & Management ❤️

6.1 Supportive Care

• Oxygen therapy for hypoxemic dogs—via oxygen cage or nasal cannula.
• Exercise restriction and avoidance of lung irritants (smoke, dust).

6.2 Medical Therapy

• Corticosteroids (e.g., prednisone): reduce inflammation in idiopathic or immune-mediated forms—often help for weeks to months.
• Antifungals (e.g., trimethoprim-sulfamethoxazole): for Pneumocystis pneumonia.
• Antibiotics: only if secondary bacterial infection is present.

7. Prognosis & Follow-Up

• Idiopathic fibrosis carries a guarded prognosis—average survival 12–18 months after diagnosis.
• Pneumocystis infection often has a more favorable outcome with appropriate treatment.
• Relapses are common—long-term low-dose steroids or periodic treatment may be needed.
• Regular imaging and respiratory function checks are essential for monitoring disease progression.

8. Home Monitoring & Ask A Vet Support 🏡

• Track resting respiratory rate, exercise tolerance, and coughing through Ask A Vet.
• Upload breathing videos and photos to aid remote monitoring.
• Medication reminders, especially for steroids or antifungals.
• Environmental checklists—air quality, air filters, avoiding irritants.
• Alerts if signs worsen, prompting re‑evaluation by vet.

🔍 Key Takeaways

• Interstitial pneumonia involves inflammation or scarring of alveolar walls, not typical airway infections.
• Common in terrier breeds and immune‑compromised dogs; causes vary from idiopathic fibrosis to Pneumocystis.
• Diagnosis relies on X‑rays, lung ultrasound, CT, BAL, and sometimes biopsy.
• Treatment is mostly supportive: oxygen, steroids, antifungals, and avoiding lung irritants.
• Long‑term prognosis varies—some stabilize, others decline gradually; monitoring is key.
• Ask A Vet helps track symptoms, manage therapy, and detect relapses early.

🩺 Conclusion ❤️

Canine interstitial pneumonia is a complex, often chronic lung condition—but modern diagnostics, supportive care, and targeted therapies offer better outcomes than ever before. Recognizing subtle signs, using imaging tools, and integrating home‑clinic support with Ask A Vet enable proactive management. With vigilance and care, many dogs maintain quality of life—even with stiffened lungs. 🐶✨

Dr Duncan Houston BVSc – dedicated to lung health and compassionate veterinary care.

Visit AskAVet.com and download the Ask A Vet app for respiratory monitoring, medication tracking, air‑filter guidance, and support through every respiratory flare‑up. ❤️