Diffuse Alveolar Haemorrhage and Pulmonary-Renal Syndromes

The answer first

Diffuse alveolar haemorrhage (DAH) is bleeding into the alveolar spaces from the pulmonary microcirculation — a syndrome, not a diagnosis. The job is never just to recognise it; it is to find which of the immune, cardiac, toxic or coagulopathic causes is bleeding, because the treatments are opposites ^{[1] [2]}. Three rules carry you through the DWE and the DCE:

1. Haemoptysis is not required. Up to a third of DAH episodes present without any haemoptysis. The real triad is a falling haemoglobin, new diffuse pulmonary infiltrates, and worsening hypoxaemia — in a ventilated ICU patient that combination, unexplained by pneumonia or pulmonary oedema, is DAH until bronchoscopy proves otherwise ^{[1] [2]}.
2. Bronchoscopy with serial lavage is the diagnostic move. Not another CT, not empiric antibiotics: bronchoalveolar lavage aliquots that become progressively bloodier, later confirmed by haemosiderin-laden macrophages ^[1].
3. The urine finishes the examination. DAH plus an active urinary sediment (haematuria, red-cell casts, rising creatinine) is the pulmonary-renal syndrome — and the shortlist is ANCA-associated vasculitis, anti-GBM disease and SLE. Same-day serology decides the treatment: plasma exchange is the cornerstone for anti-GBM, while rituximab or cyclophosphamide anchors ANCA vasculitis — and after PEXIVAS, plasma exchange is no longer routine for ANCA disease ^{[7] [12] [16]}.

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References19ShowHide

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