Diffuse alveolar haemorrhage and pulmonary-renal syndromes

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Alveolar haemorrhage is a syndrome, not an aetiology. Pulmonary capillaritis from ANCA-associated vasculitis, anti-GBM antibodies or lupus causes inflammatory vessel injury. Bland haemorrhage may follow anticoagulation, severe coagulopathy, mitral disease or elevated venous pressure, while diffuse alveolar damage can bleed in infection, transplantation or toxic injury. The distinction directs immunosuppression and plasma exchange.

Clinical severity varies from anaemia and patchy ground-glass change to fulminant hypoxaemic failure. Haemoglobin may initially appear preserved because bleeding and plasma-volume change occur together. Bronchoalveolar lavage that becomes progressively bloodier supports ongoing alveolar bleeding; haemosiderin-laden macrophages appear later and do not identify the cause.

Pulmonary–renal disease is time-critical because both organs can decline over hours to days. Respiratory support, kidney assessment, serology, cultures and tissue planning happen in parallel. BSR published UK management recommendations for ANCA-associated vasculitis in 2025, and NHS England updated its rituximab policy page in 2026. Exact induction, steroid reduction, plasma-exchange and prophylaxis regimens remain specialist and must be checked live.

Key points

Diffuse alveolar haemorrhage is bleeding into the alveolar space from pulmonary microvasculature; haemoptysis may be absent, especially in intubated or severely ill patients.
The core pattern is acute breathlessness or hypoxaemia, new bilateral ground-glass or air-space opacity, falling haemoglobin and bloodier sequential lavage aliquots when bronchoscopy is safe.
Pulmonary–renal syndrome combines alveolar haemorrhage with glomerulonephritis, classically from ANCA-associated vasculitis, anti-GBM disease or systemic lupus erythematosus.
Urinalysis is a rapid high-value test: blood, protein and casts with rising creatinine make a capillaritic pulmonary–renal process much more likely.
Normal coagulation or absent haemoptysis does not exclude haemorrhage. Anticoagulation and thrombocytopenia may cause bland bleeding but do not explain active urinary sediment.
Send PR3-ANCA, MPO-ANCA, anti-GBM antibodies, ANA, dsDNA and complement early, but interpret them with phenotype and tissue because false-positive and seronegative disease occur.
Bronchoscopy supports diagnosis and infection sampling but can destabilise severe hypoxaemia; do not require it before urgent expert treatment when the clinical picture is compelling.
Kidney biopsy often provides safer and more specific tissue than lung biopsy when glomerulonephritis is present.
Severe ANCA-associated disease is induced with glucocorticoids plus rituximab or cyclophosphamide under specialist guidance. Anti-GBM disease often requires urgent plasma exchange as part of a distinct protocol.
Infection, drug toxicity and immune haemorrhage can coexist. Immunosuppression demands active microbiological assessment and prophylaxis planning.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Small-vessel vasculitis

ANCA-associated vasculitis can inflame pulmonary capillaries and glomeruli, causing simultaneous alveolar bleeding and rapidly progressive renal injury.

Anti-basement-membrane disease

Autoantibodies directed against shared alveolar and glomerular basement-membrane targets produce a particularly urgent pulmonary-renal syndrome, with host defence and baseline lung health modifying its clinical effect.

Autoimmune and immune-complex disease

Lupus and other systemic autoimmune disorders may cause capillaritis, bland haemorrhage or glomerulonephritis through immune-complex injury.

Non-immune bleeding

Anticoagulation, severe coagulopathy, cardiac congestion, infection, inhaled toxins and transplantation can cause alveolar haemorrhage without primary vasculitis.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Capillary injury
Immune inflammation or non-inflammatory disruption breaches the pulmonary microvascular barrier and allows blood into alveolar spaces.
2
Alveolar flooding
Accumulating erythrocytes and plasma displace air, reduce ventilation and create rapidly progressive shunt and hypoxaemia, with effects that increase as the pathological process progresses.
3
Haemoglobin loss
Ongoing occult or visible pulmonary bleeding lowers circulating haemoglobin, further compromising systemic oxygen delivery, contributing to the resulting loss of respiratory reserve.
4
Parallel glomerular damage
When shared autoimmune targets involve kidneys, capillary inflammation causes haematuria, proteinuria and rapidly declining filtration alongside lung injury.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Diffuse alveolar haemorrhageRed flag

Acute hypoxaemia, diffuse or patchy bilateral ground-glass opacity and a falling haemoglobin suggest DAH; haemoptysis strengthens but is not required for the diagnosis.

Pulmonary–renal syndromeRed flag

Haematuria, proteinuria, red-cell casts or rapidly rising creatinine alongside pulmonary haemorrhage indicates glomerulonephritis and needs immediate nephrology and vasculitis assessment.

ANCA-associated vasculitisRed flag

ENT disease, mononeuritis multiplex, purpura, constitutional symptoms, orbital inflammation or pulmonary nodules accompany capillaritis in granulomatosis with polyangiitis or microscopic polyangiitis.

Anti-GBM diseaseRed flag

Abrupt severe alveolar haemorrhage with rapidly progressive glomerulonephritis, sometimes after smoking or hydrocarbon exposure, requires immediate anti-GBM testing and specialist plasma-exchange consideration.

Bland or medicine-related haemorrhageRed flag

Anticoagulation, thrombocytopenia, coagulopathy, severe left-sided filling pressure or selected drugs may cause bleeding without systemic capillaritis; active urinary sediment argues for an immune process.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
FBC, serial haemoglobin, platelets and coagulation screenFirst step
Why
Detect blood loss, thrombocytopenia and a reversible haemostatic contributor.
Interpretation and limitations
A normal first haemoglobin does not exclude acute bleeding. Trend alongside transfusion, fluids and haemolysis markers; correct severe coagulopathy while finding the cause.
02
Urinalysis, urine microscopy, protein quantification and renal profile
Why
Identify glomerular bleeding and rapidly progressive kidney injury.
Interpretation and limitations
Dysmorphic red cells or red-cell casts, proteinuria and rising creatinine support glomerulonephritis. A bland urine makes pulmonary–renal vasculitis less likely but not impossible.
03
ANCA with PR3 and MPO specificity, and anti-GBM antibodies
Why
Identify the leading antibody-associated pulmonary–renal syndromes rapidly.
Interpretation and limitations
Interpret titres and specificity with phenotype; infection and other inflammation can produce ANCA, while a negative assay does not fully exclude capillaritis. Dual positivity affects prognosis and relapse planning.
04
ANA, dsDNA, complement and additional immune tests
Why
Assess lupus, immune-complex disease and alternative systemic autoimmunity.
Interpretation and limitations
Low complement and compatible lupus serology redirect treatment. Broad positive screening without clinical correlation can mislead, particularly during infection.
05
Chest radiograph and high-resolution CT
Why
Define distribution, severity and alternatives such as infection, oedema, nodules or embolic disease.
Interpretation and limitations
Ground-glass opacity and consolidation are nonspecific. Rapid clearing can support haemorrhage, while cavitating nodules suggest granulomatous vasculitis or infection.
06
Bronchoscopy with sequential bronchoalveolar lavage
Why
Support alveolar bleeding and obtain microbiology when the patient can tolerate the procedure.
Interpretation and limitations
Aliquots becoming progressively bloodier support DAH. Haemosiderin macrophages are delayed; a traumatic bronchial sample does not show the same serial pattern.
07
Kidney biopsy
Why
Establish pauci-immune, anti-GBM or immune-complex glomerulonephritis and guide prognosis and treatment.
Interpretation and limitations
Biopsy is often more informative and safer than lung tissue when urinary and renal abnormalities are present, but life-saving treatment may precede biopsy in fulminant disease.
08
Blood and respiratory microbiology
Why
Identify infection before and during immunosuppression.
Interpretation and limitations
Take cultures and targeted viral or opportunistic tests promptly. Infection does not exclude vasculitis and may trigger relapse or coexist with treatment toxicity.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Multifocal pneumonia

Fever and bilateral opacities overlap, but falling haemoglobin, renal sediment and increasingly bloody lavage favour haemorrhage; infection may still coexist.

Cardiogenic pulmonary oedema

Raised cardiac filling pressures and congestion cause bilateral alveolar shadowing and occasionally blood-stained sputum without pulmonary capillaritis.

Acute respiratory distress syndrome

Diffuse permeability oedema produces similar hypoxaemia and imaging but lacks direct evidence of alveolar bleeding or glomerulonephritis.

Pulmonary embolism with infarction

Pleuritic pain and haemoptysis with focal peripheral change suggest infarction rather than diffuse microvascular bleeding, while chronology and directed testing distinguish the competing explanation.

Upper-airway or gastrointestinal bleeding

Nasopharyngeal or gastrointestinal blood can be coughed or aspirated; careful source assessment distinguishes pseudohaemoptysis from primary alveolar haemorrhage.

Additional chapter-specific clues

Mimic or coexisting infectionRed flag

Severe bilateral pneumonia, oedema and ARDS can look identical. Fever, immunosuppression and focal consolidation require broad microbiological sampling even when immune disease is likely.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01First hoursStabilise and recognise the syndromeFirst stepHypoxaemia with bilateral opacities, haemoptysis or unexplained haemoglobin fall.

1Use ABCDE care, controlled oxygen and early critical-care support; crossmatch blood and assess the need for invasive ventilation.
2Stop or reverse anticoagulation and correct severe haemostatic defects when clinically justified, balancing thrombosis risk.
3Send FBC, coagulation, renal profile, urinalysis, ANCA, anti-GBM, lupus tests and microbiology immediately.
4Involve respiratory, renal and rheumatology teams together and treat severe infection in parallel when plausible.

02ConfirmSeparate capillaritis from bland haemorrhageDAH is suspected after initial imaging and laboratory assessment.

1Review medicines, anticoagulation, valve and cardiac disease, toxin exposure, systemic vasculitic features and recent infection.
2Use CT to guide the differential and bronchoscopy with sequential lavage if oxygenation and procedural risk permit.
3When renal involvement is present, plan urgent kidney biopsy because tissue classification directs induction and prognosis.
4Do not delay specialist induction treatment for a compelling life-threatening pulmonary–renal syndrome solely to await bronchoscopy or biopsy.

03Immune diseaseInduce remission safelyANCA-associated vasculitis, anti-GBM disease or lupus capillaritis is likely or confirmed.

1Use specialist glucocorticoid induction plus rituximab or cyclophosphamide for severe ANCA-associated disease under the current BSR pathway.
2Discuss plasma exchange urgently for anti-GBM disease and selected exceptional vasculitis scenarios; it is not an automatic treatment for every DAH.
3Plan infection prophylaxis, vaccination, fertility preservation, bone and gastric protection, and screening required for the chosen immunosuppressant.
4Define remission, steroid-reduction and maintenance plans with coordinated renal, respiratory and rheumatology follow-up.

04DeteriorationSupport two failing organsWorsening hypoxaemia, falling haemoglobin, oligo-anuria, hyperkalaemia or severe acidosis.

1EscalationEscalate lung-protective ventilation and transfusion according to physiology, avoiding excessive volume in injured lungs and renal failure.
2Start renal replacement therapy for standard urgent indications through nephrology; dialysis does not replace disease-specific induction.
3Reassess for infection, ongoing bleeding, pulmonary embolism, fluid overload and treatment toxicity when response is poor.
4Discuss ECMO or other rescue support early in potentially reversible refractory failure, accounting for bleeding and anticoagulation complexity.

Key medicines and prescribing safety4 treatments · regimens, roles and cautions

Rapidly suppresses pulmonary capillaritis while definitive remission-induction therapy takes effect.

Systemic glucocorticoid induction

Use a specialist acute regimen followed by a protocolised reduction, selected for disease severity, age, infection risk and the current BSR recommendation.

High exposure increases infection, hyperglycaemia, delirium, myopathy, gastrointestinal and bone harm. Obtain microbiology promptly and use prophylaxis and monitoring rather than prolonging empirically.

B-cell depletion for remission induction in severe ANCA-associated vasculitis and selected maintenance strategies.

Rituximab

Give only through the vasculitis service using a licensed or commissioned induction schedule, with pre-infusion screening and current product information.

Screen hepatitis B, immunoglobulins, infection and vaccination status; infusion reactions, late neutropenia and hypogammaglobulinaemia require monitoring. It is not immediate mechanical haemostasis.

Potent remission induction for organ- or life-threatening capillaritic disease, including selected ANCA, anti-GBM and lupus syndromes.

Cyclophosphamide

Use a renal-, age- and blood-count-adjusted specialist oral or intravenous regimen within the current vasculitis protocol.

Myelosuppression, infection, bladder toxicity, malignancy and gonadal toxicity are major risks. Discuss fertility preservation where feasible and monitor blood count, urine and cumulative exposure.

Rapidly removes pathogenic antibody in anti-GBM disease and selected exceptional immune pulmonary–renal presentations.

Plasma exchange

Deliver as a specialist procedure according to the current anti-GBM or selected vasculitis protocol, with replacement fluid and session schedule individualised.

Not routine for every ANCA-associated DAH. Bleeding, infection, hypotension, hypocalcaemia and removal of therapeutic antibodies or medicines require coordinated planning.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Acute respiratory failure

Diffuse blood-filled alveoli cause profound hypoxaemia, reduced compliance and possible need for invasive support, adding morbidity beyond the initial pulmonary disorder.

Rapid kidney failure

Untreated crescentic glomerulonephritis can destroy filtration over days, causing fluid, electrolyte and uraemic complications, adding morbidity beyond the initial pulmonary disorder.

Severe anaemia

Pulmonary blood loss may be substantial even without haemoptysis, reducing oxygen delivery and cardiovascular reserve, particularly when baseline cardiopulmonary reserve is limited.

Thrombotic and bleeding conflict

Active haemorrhage complicates anticoagulation decisions when pulmonary embolism or extracorporeal support is also possible, particularly when baseline cardiopulmonary reserve is limited.

Immunosuppression-related infection

Urgent immune treatment can permit serious opportunistic infection, which may clinically mimic recurrent haemorrhage or vasculitic activity.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Trend oxygen requirement, respiratory rate, blood gases, imaging, airway blood burden and ventilatory pressures in a critical-care setting when severe.
Measure haemoglobin, platelets and coagulation repeatedly, accounting for fluid shifts and transfusion rather than relying on one value.
Track creatinine, urine output, potassium, bicarbonate, urine blood and protein to judge renal injury and dialysis need.
Follow PR3- or MPO-ANCA and anti-GBM results as contextual markers, but make acute decisions from organ trajectory and tissue rather than titre alone.
During immunosuppression monitor blood count, liver and renal function, glucose, infection, immunoglobulins and agent-specific toxicity and prophylaxis.
After remission, monitor for relapse through symptoms, urinalysis, renal function and specialist review; recurrent haemoptysis is not the only warning.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

No haemoptysis does not reassure

Blood can remain in distal air spaces or be swallowed, and an intubated patient may not cough. Use haemoglobin, imaging and lavage context.

Urinalysis can change the emergency

A bedside dip showing blood and protein in diffuse pulmonary disease may reveal a life-threatening pulmonary–renal syndrome before serology returns.

Kidney tissue often answers the lung question

Pauci-immune, linear anti-GBM or immune-complex staining can distinguish mechanisms without the greater risk of surgical lung biopsy in a hypoxaemic patient.

ANCA is not a diagnosis

Infection, inflammatory bowel disease, medicines and other conditions can produce ANCA. Specificity, phenotype, urine and tissue determine meaning.

Plasma exchange is mechanism-specific

It remains central to anti-GBM disease but has a narrower, debated role in ANCA vasculitis. Use the current specialist guideline, not the severity of haemoptysis alone.

11Common pitfallsFrequent interpretation and management errors.

01
Excluding DAH because haemoptysis is absent.
02
Missing urinalysis in a patient with diffuse pulmonary infiltrates.
03
Treating a positive ANCA as proof without excluding infection and obtaining tissue where feasible.
04
Delaying life-saving specialist treatment until bronchoscopy in an unstable patient.
05
Using plasma exchange automatically for every ANCA-associated haemorrhage.
06
Starting intense immunosuppression without microbiology, prophylaxis and toxicity planning.
07
Assuming anticoagulation is the whole cause when active glomerular urine sediment is present.