A 32-year-old man develops progressive hypoxemia 18 hours after aspiration of gastric contents during an emergency intubation. Chest radiograph shows bilateral diffuse infiltrates. PaO2/FiO2 ratio is 140 mmHg with no evidence of cardiac failure. Which histological pattern would be seen in the exudative phase?

• A Non-caseating epithelioid granulomas along lymphatic routes
• B Temporal heterogeneity with fibroblastic foci and honeycombing
• C Hyaline membranes lining alveolar ducts with interstitial and intra-alveolar edema ✓
• D Alveolar spaces filled with lipid-laden macrophages

Explanation

Aspiration-induced acute lung injury progressing to ARDS shows diffuse alveolar damage. The exudative phase features interstitial and intra-alveolar edema, denudation of alveolar epithelium, and eosinophilic hyaline membranes lining alveolar ducts, with a PaO2/FiO2 below 200 mmHg confirming ARDS here. Fibroblastic foci with temporal heterogeneity define usual interstitial pneumonia, and lipid-laden macrophages indicate exogenous lipoid pneumonia.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.