Skip to content
How It Works
Explore
Resources Ask a Question
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 17 peer-reviewed journal articles Updated
Pulmonology

Diagnosis and Understanding Your BAL Results

At a Glance

Diffuse Alveolar Hemorrhage (DAH) is definitively diagnosed using a bronchoalveolar lavage (BAL) procedure to check for deep lung bleeding. Finding progressively bloody fluid and more than 20% hemosiderin-laden macrophages in the lung wash confirms DAH. Doctors also use CT imaging and blood tests.

When you are being evaluated for Diffuse Alveolar Hemorrhage (DAH), your doctors are essentially trying to prove two things: first, that you are actively bleeding into your air sacs, and second, why it is happening. This involves a combination of looking inside your lungs, analyzing your blood, and sometimes checking your kidney tissue [1][2].

The Gold Standard: Bronchoalveolar Lavage (BAL)

The most definitive way to confirm DAH is through a bronchoscopy with bronchoalveolar lavage (BAL). During this procedure, a doctor passes a thin camera into your airways and performs a “lung wash” by injecting a small amount of salt water and then suctioning it back out [1].

  • Progressive Bleeding: The “gold standard” finding for DAH is when the fluid suctioned out becomes progressively bloodier with each sequential sample (aliquot) taken [3][4]. This tells the doctor that the blood is coming from the deep air sacs rather than a single injury in a larger airway.
  • Hemosiderin-Laden Macrophages: Your doctors will also send this fluid to a lab to look for hemosiderin-laden macrophages. Macrophages are “clean-up cells” in your immune system. When blood leaks into the lungs, these cells eat the red blood cells [5]. Hemosiderin is the iron-rich stain left behind after the cell digests the blood [5][1].
  • The Threshold: Finding that 20% or more of these clean-up cells are stained with hemosiderin is a strong indicator that you have DAH [6][7].

Advanced Imaging: HRCT

While a standard X-ray can show “shadows,” a High-Resolution CT (HRCT) scan provides a much clearer picture of the damage. In DAH, doctors typically look for:

  • Ground-Glass Opacities: Hazy, gray areas that look like frosted glass, indicating the air sacs are partially filled with fluid or blood [8][9].
  • Crazy-Paving Pattern: A specific look where these hazy areas have thickened lines running through them, showing significant inflammation [10].

Why the Kidney Biopsy?

If your doctors suspect pulmonary-renal syndrome (where both the lungs and kidneys are involved), they may ask to biopsy your kidney instead of your lung. There are two main reasons for this:

  1. Safety: Lung tissue is very delicate, and biopsying a lung that is already bleeding is risky [11]. Kidney biopsies are generally considered safer and easier to perform under ultrasound guidance [11][12].
  2. Clarity: The kidneys often provide a “cleaner” look at the underlying cause. Inflammation in the kidney (like crescentic glomerulonephritis) is easier for pathologists to categorize, helping them distinguish between conditions like ANCA-associated vasculitis and Anti-GBM disease [2][13].

Completeness Checklist: The “DAH Panel”

To find the underlying cause, your medical team should run a series of specialized blood tests (serology). Ensure these have been ordered:

  • [ ] Complete Blood Count (CBC) with Platelets: To measure the extent of the anemia and check for low platelets, which can worsen bleeding [1].
  • [ ] Coagulation Studies (PT/INR, PTT): To ensure your blood is still capable of clotting normally [7].
  • [ ] ANCA (Antineutrophil Cytoplasmic Antibodies): To check for common types of vasculitis [14].
  • [ ] Anti-GBM Antibodies: To check for Goodpasture’s syndrome [15].
  • [ ] ANA (Antinuclear Antibody): To screen for Lupus (SLE) [16].
  • [ ] Urinalysis: To look for blood or protein that suggests your kidneys are involved [13].
  • [ ] Infection Screen: To rule out viral or bacterial triggers like Mycoplasma [17].

Common questions in this guide

What does a progressively bloody BAL result mean?
During a bronchoscopy, doctors wash the lung with fluid and collect samples. If the fluid becomes bloodier with each consecutive sample taken, it is a strong sign that the bleeding is coming from the deep air sacs, which is the gold standard finding for diffuse alveolar hemorrhage.
What are hemosiderin-laden macrophages?
Macrophages are immune system clean-up cells. When blood leaks into your lungs, these cells consume the red blood cells, leaving behind an iron-rich stain called hemosiderin. If 20% or more of these cells in your lung wash have this stain, it strongly indicates DAH.
Why might my doctor order a kidney biopsy for a lung bleeding problem?
Conditions that cause lung bleeding often affect the kidneys as well, a condition known as pulmonary-renal syndrome. A kidney biopsy is generally safer to perform than biopsying a bleeding lung, and the kidney tissue often provides a clearer picture of the underlying disease.
What will a CT scan show if I have diffuse alveolar hemorrhage?
A high-resolution CT scan of the lungs may show 'ground-glass opacities,' which look like hazy, frosted glass indicating fluid or blood in the air sacs. It might also show a 'crazy-paving pattern,' signifying significant inflammation.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.During my bronchoscopy, did the fluid become progressively bloodier with each sample taken?
  2. 2.What percentage of the macrophages in my lung wash were 'hemosiderin-laden'?
  3. 3.Since I have both lung and kidney symptoms, why is a kidney biopsy safer or more informative than a lung biopsy?
  4. 4.Which specific antibody tests (like ANCA or Anti-GBM) have come back positive so far?
  5. 5.Does my CT scan show the 'ground-glass' or 'crazy-paving' patterns typical of DAH?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (17)
  1. 1

    Diffuse Alveolar Hemorrhage.

    Murray J, O'Brien S, Mitchell PD

    Seminars in respiratory and critical care medicine 2025; doi:10.1055/a-2725-7274.

    PMID: 41130281
  2. 2

    PULMONARY HEMORRHAGE AND CRESCENTIC GLOMERULONEPHRITIS IN A PATIENT WITH SEROPOSITIVE ANTI-GLOMERULAR BASEMENT MEMBRANE DISEASE AND ANTI-NEUTROPHIL CYTOPLASMIC ANTIBODIES.

    Sreter KB, Pavlović D, Tomić M, et al.

    Acta clinica Croatica 2022; (61(3)):528-533 doi:10.20471/acc.2022.61.03.19.

    PMID: 37492353
  3. 3

    Diffuse Alveolar Hemorrhage Caused by Metastatic Breast Cancer.

    Higashiguchi M, Yoshioka S, Mizukoshi T, et al.

    Internal medicine (Tokyo, Japan) 2026; (65(4)):547-551 doi:10.2169/internalmedicine.5457-25.

    PMID: 40707218
  4. 4

    Legionella pneumonia associated with severe acute respiratory distress syndrome and diffuse alveolar hemorrhage - A rare association.

    Kashif M, Patel R, Bajantri B, Diaz-Fuentes G

    Respiratory medicine case reports 2017; (21()):7-11 doi:10.1016/j.rmcr.2017.03.008.

    PMID: 28348947
  5. 5

    An Adult Case of Idiopathic Pulmonary Hemosiderosis Associated with Pulmonary Fibrosis and Emphysematous Change.

    Kono M, Oshima Y, Katsumata M, et al.

    Internal medicine (Tokyo, Japan) 2024; (63(1)):119-124 doi:10.2169/internalmedicine.1663-23.

    PMID: 37225487
  6. 6

    A Rare Case of Diffuse Alveolar Hemorrhage Caused by Fentanyl Inhalation.

    Nangrani A, Chung J, Jyang E, et al.

    Cureus 2023; (15(10)):e47598 doi:10.7759/cureus.47598.

    PMID: 38022247
  7. 7

    Anticoagulant Use as an Independent Risk Factor and Higher In-Hospital Mortality in Patients Showing Alveolar Hemorrhage in Diffuse Lung Disease.

    Ugajin M, Kani H, Hattori H

    Medicina (Kaunas, Lithuania) 2021; (57(10)) doi:10.3390/medicina57101094.

    PMID: 34684131
  8. 8

    Diffuse Alveolar Hemorrhage in an Undiagnosed Systemic Lupus Erythematosus Patient.

    Salah QM, Albandak M, Ayyad M, et al.

    Cureus 2023; (15(5)):e38421 doi:10.7759/cureus.38421.

    PMID: 37273395
  9. 9

    Diffuse Alveolar Hemorrhage Caused by Warfarin after Rifampicin Discontinuation.

    Kiyota T, Shiota S, Hamanaka R, et al.

    Case reports in medicine 2019; (2019()):4917856 doi:10.1155/2019/4917856.

    PMID: 30809261
  10. 10

    The Clinical Significance of a 'Crazy-Paving' Pattern on Chest Radiology.

    Ehab A, Braga RI

    European journal of case reports in internal medicine 2018; (5(12)):000978 doi:10.12890/2018_000978.

    PMID: 30755996
  11. 11

    Optimizing renal biopsy: efficacy and safety of the ultrasound-guided tangential approach.

    Pinto-Silva RA, Pereira MBD, Panzi Neto MD, et al.

    Radiologia brasileira 2025; (58()):e20240132 doi:10.1590/0100-3984.2024.0132-en.

    PMID: 40568419
  12. 12

    Optimization of Pediatric Kidney Biopsy: Impact of Needle Size and Passes.

    Yasar Y, Coskun M, Yasar E, et al.

    Academic radiology 2025; (32(6)):3659-3666 doi:10.1016/j.acra.2025.04.019.

    PMID: 40274519
  13. 13

    Pulmonary renal syndrome: a clinical review.

    Boyle N, O'Callaghan M, Ataya A, et al.

    Breathe (Sheffield, England) 2022; (18(4)):220208 doi:10.1183/20734735.0208-2022.

    PMID: 36865943
  14. 14

    Diffuse Alveolar Hemorrhage in Autoimmune Diseases.

    Martínez-Martínez MU, Oostdam DAH, Abud-Mendoza C

    Current rheumatology reports 2017; (19(5)):27 doi:10.1007/s11926-017-0651-y.

    PMID: 28397125
  15. 15

    Splenic Infarcts and Pulmonary Renal Syndrome in a Young Patient with Double-Positive Anti-GBM and ANCA-Associated Vasculitis.

    Rajah FT, Alhabobi AA, Aloudah NM, et al.

    Saudi journal of kidney diseases and transplantation : an official publication of the Saudi Center for Organ Transplantation, Saudi Arabia 2021; (32(1)):240-244 doi:10.4103/1319-2442.318532.

    PMID: 34145139
  16. 16

    Systemic lupus erythematosus and diffuse alveolar hemorrhage, etiology and novel treatment strategies.

    Al-Adhoubi NK, Bystrom J

    Lupus 2020; (29(4)):355-363 doi:10.1177/0961203320903798.

    PMID: 32036761
  17. 17

    Severe pediatric Mycoplasma pneumonia as the cause of diffuse alveolar hemorrhage requiring veno-venous extracorporeal membrane oxygenation: A case report.

    Zhang X, Yu Y

    Frontiers in pediatrics 2022; (10()):925655 doi:10.3389/fped.2022.925655.

    PMID: 36683817

This page explains the diagnostic process and lab results for Diffuse Alveolar Hemorrhage for educational purposes only. Always consult your pulmonologist or medical team for proper interpretation of your specific tests and biopsies.

Get notified when new evidence is published on Diffuse alveolar hemorrhage.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.