Page 1112 - Cote clinical veterinary advisor dogs and cats 4th

554 Interstitial Lung Diseases

• Respiratory distress • Pneumonia (infectious, aspiration, foreign TREATMENT
body)
• Exercise intolerance • Neoplasia Treatment Overview
VetBooks.ir Nonrespiratory signs: • Pulmonary thromboembolism Treatment consists of removing or addressing
• Hemoptysis
• Cardiogenic or non-cardiogenic pulmonary
• Fever
the inciting cause if it can be identified. If
edema
• Lethargy
• Anorexia • Pleural effusion or pneumothorax no underlying cause can be identified, treat-
ment is focused on decreasing inflammation.
• Weight loss Radiographic: No treatments are known to directly halt the
• Syncope (associated with pulmonary hyper- • Infectious pneumonia (bacterial, fungal, viral, progression of fibrosis.
tension [PH] or intermittent hypoxemia) protozoal, parasitic)
• Noncardiogenic pulmonary edema Acute General Treatment
PHYSICAL EXAM FINDINGS • Neoplasia Oxygen supplementation is indicated for
• Spontaneous or elicited cough (productive hypoxemic patients in respiratory distress
or nonproductive) Initial Database (p. 1146). Many affected patients are comfort-
• Pulmonary crackles on auscultation (inspira- • CBC able with mild to moderate chronic arterial
tory, with pulmonary fibrosis) ○ ± Inflammatory leukogram ± polycythemia hypoxemia.
• Increased respiratory rate and/or effort if chronic hypoxemia
(inspiratory and expiratory) ○ Eosinophilia present in 50%-60% of dogs Chronic Treatment
• Right-sided systolic heart murmur may be with eosinophilic pneumonia • Remove potential inciting causes.
ausculted if PH is present (with tricuspid • Thoracic radiographs ○ Consider discontinuation of any drug
regurgitation). ○ Interstitial, alveolar (severe disease), or not immediately critical for the patient’s
○ Unlike primary heart disease, tachycardia bronchointerstitial patterns health.
is absent, may have sinus arrhythmia ○ Interstitial nodules • Eosinophilic pneumonias: treat underlying
• Fever ○ Hypoinflation cause (e.g., heartworm, other parasites,
• Poor body condition ○ ± Hilar lymphadenopathy fungi) if identified. If none found, treat with
• ± Cyanosis ○ ± Right-sided cardiomegaly from cor immunosuppressive doses of glucocorticoids.
pulmonale ○ Oral glucocorticoids are preferred for dogs
Etiology and Pathophysiology • Arterial blood gas or pulse oximetry > 10 kg. Inhaled glucocorticoid therapy
• ILDs result from injury to alveolar epithelial ○ ± Hypoxemia (fluticasone) may be effective in small dogs
cells and a cycle of inflammation and repara- ○ ± Hypocarbia and can reduce systemic side effects of
tive responses that proceed unchecked. • Six-minute walk test may provide an objective long-term oral glucocorticoids (p. 298).
○ In humans, injury can be triggered by assessment of exercise tolerance. • If present, PH may be addressed with
Inhalation of toxins, irritants, or • Fecal flotation or sedimentation (Baermann): sildenafil 1-2 mg/kg PO q 12h.
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allergens respiratory parasites • For most other ILDs, immunosuppression
Vascular damage from drugs • Infectious disease testing for agents endemic has been advocated (provided infection
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Collagen-related vascular diseases to patient’s geographic region is definitively ruled out), starting with
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Systemic immune-mediated diseases glucocorticoids (e.g., prednisone 2 mg/kg
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Infection Advanced or Confirmatory Testing PO q 24h).
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Neoplasia • CT provides more specific information on ○ Empirically (i.e., without scientific
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○ Many veterinary cases are idiopathic. the extent, pattern, and location of disease. evidence of their efficacy), other immu-
• Alveolar epithelial cell injury leads to A ground-glass pattern is a common CT nosuppressive drugs have been tried in
○ Inflammatory cell influx characteristic for dogs with pulmonary refractory cases.
○ Release of proinflammatory and fibrogenic fibrosis.
mediators • Bronchoscopy, bronchoalveolar lavage (p. Behavior/Exercise
○ Deposition of extracellular matrix 1074), and fine-needle aspiration (p. 1113) Minimize exposure to inhalant fumes, chemi-
○ Structural changes, including fibrosis for cytologic evaluation and culture can cals, dusts, or other known disease triggers.
• Idiopathic pulmonary fibrosis appears to be provide evidence of underlying infection or
a fibroproliferative disorder that originates neoplasia if microorganisms or neoplastic Possible Complications
independently of inflammation (i.e., inflam- cells are identified: • Decompensation during and after bronchos-
mation is secondary). ○ Nonspecific inflammatory cells or poor copy or lung biopsy, especially in patients
○ Injured alveolar epithelial cells are still critical cellularity is seen with ILDs. with a significant degree of respiratory
for triggering and sustaining fibrogenesis. ○ Absence of microorganisms or neoplastic compromise at rest
cells does not rule out these causes of • Immunosuppression can predispose to
DIAGNOSIS respiratory disease. secondary infections.
• Lung biopsy is the only definitive means for ○ After lung biopsy, allow the incision to
Diagnostic Overview diagnosis. heal before administering immunosup-
Diagnosis is suspected in patients with clini- ○ Can be performed by a keyhole technique, pressive medication.
cal signs and imaging features (radiographic, thoracoscopy, or thoracotomy • These patients may be predisposed to
CT) consistent with ILD in which there is ○ Special stains are indicated to rule out pneumonia due to compromise of normal
no evidence of infectious or neoplastic causes infectious agents. respiratory defense mechanisms.
of respiratory disease. A definitive diagnosis • Echocardiogram (p. 1094) to evaluate for
requires lung biopsy for histopathologic exam. PH, if indicated. Recommended Monitoring
• Various serum and bronchoalveolar lavage • Clinical signs
Differential Diagnosis fluid biomarkers (e.g.; endothelin-1, CCLX, • Periodic physical exam, arterial blood gas (if
Physical exam (cough/respiratory distress): CXCL8) have shown promise in a research significant respiratory compromise), thoracic
• Other airway diseases (e.g., chronic bron- setting to aid in the diagnosis of idiopathic radiographs, 6-minute walk test
chitis, eosinophilic bronchitis, obstructive pulmonary fibrosis. • Echocardiogram (if indicated to monitor
airway diseases) PH)

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