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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Pulmonology

Diagnosis & The 'Idiopathic' Label

At a Glance

An 'idiopathic' bronchiectasis diagnosis means doctors haven't found a specific cause for your widened airways. This label should only be given after a comprehensive workup—including an HRCT lung scan, immune function tests, and cystic fibrosis screening—has ruled out all other conditions.

Being told your bronchiectasis is “idiopathic” means your medical team has not yet found a specific underlying disease that caused your airways to widen. However, “idiopathic” should only be used as a final label after a rigorous, systematic diagnostic workup has ruled out every other possibility [1][2].

The Gold Standard: HRCT

The gold standard for diagnosing bronchiectasis is a High-Resolution Computed Tomography (HRCT) scan [3][4]. Unlike a standard chest X-ray, which often looks normal in early disease, an HRCT takes very thin, detailed “slices” of the lungs.

Radiologists look for specific signs on these scans:

  • The Signet Ring Sign: In a healthy lung, the airway (bronchus) is the same size as the blood vessel next to it. In bronchiectasis, the airway becomes much larger than the vessel, looking like a diamond ring (the “signet ring”) [5].
  • Lack of Tapering: Healthy airways get smaller as they reach the edges of the lungs. Bronchiectatic airways stay large and wide even at the very outer edges [5][6].
  • Wall Thickening: The walls of the airways may appear thick and scarred, which is a sign of chronic inflammation [7].

The Diagnostic Workup

Before settling on an idiopathic diagnosis, international guidelines recommend a systematic series of tests. This is crucial because identifying a specific cause often changes the treatment plan [8][9].

A thorough workup should investigate:

  1. Immune Function: Blood tests to measure immunoglobulins (IgG, IgA, IgM). If the body is not making enough antibodies, it cannot fight off the infections that cause airway damage [1][2].
  2. Cystic Fibrosis (CF): While often associated with children, some adults have milder forms of CF that are not caught until later in life. This is ruled out via a sweat chloride test or genetic testing [2][10].
  3. Allergic Bronchopulmonary Aspergillosis (ABPA): This is an extreme allergic reaction to a common fungus (Aspergillus). It can be diagnosed with blood tests for specific antibodies and IgE levels [11][12].
  4. Primary Ciliary Dyskinesia (PCD): A rare genetic condition where the tiny hairs (cilia) in the lungs do not move correctly. This is often suspected if the patient has lifelong sinus or ear issues [13][14].

Why the Workup Matters

Research shows that when a truly rigorous diagnostic protocol is applied, many patients initially labeled as “idiopathic” are re-classified with a specific cause [15]. Studies indicate that between 40% and 66% of patients may eventually be found to have an underlying cause—such as a previous infection, an autoimmune issue, or an immune deficiency—if the testing is thorough enough [15][16].

Finding a cause is important because it can lead to targeted treatments. For example, if an immune deficiency is found, the patient might receive antibody infusions that significantly reduce the number of lung infections [8][17]. Even if the diagnosis remains idiopathic after a full workup, patients can feel confident that they are receiving the most accurate management for their specific situation. If you have already been given the “idiopathic” label, it is appropriate to explicitly ask your doctor to review your file together to ensure all of these conditions have been systematically ruled out.

Common questions in this guide

What does an idiopathic bronchiectasis diagnosis mean?
Being diagnosed with idiopathic bronchiectasis means that your medical team has not yet found a specific underlying disease causing your widened airways. This label should only be used after a comprehensive set of tests has ruled out all other possible causes.
How is bronchiectasis diagnosed?
The gold standard for diagnosing bronchiectasis is a High-Resolution Computed Tomography (HRCT) scan. This detailed imaging allows radiologists to see specific signs of airway widening, such as the signet ring sign, that standard chest X-rays often miss.
What tests should I have before my bronchiectasis is called idiopathic?
Before accepting an idiopathic diagnosis, you should undergo a rigorous diagnostic workup. This typically includes blood tests for immune function, sweat chloride or genetic testing for cystic fibrosis, and screenings for severe fungal allergies and primary ciliary dyskinesia.
What is the signet ring sign on an HRCT lung scan?
The signet ring sign is a specific pattern seen on an HRCT scan where an airway has become abnormally larger than the blood vessel next to it. It resembles a diamond ring and is a key visual indicator used by radiologists to confirm bronchiectasis.
Why is it important to find the underlying cause of my bronchiectasis?
Finding the specific cause of your airway damage can significantly change your treatment plan. For example, if testing reveals an underlying immune deficiency, you may be eligible for targeted treatments like antibody infusions that help prevent future lung infections.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Does my HRCT show a 'signet ring sign' or other specific patterns that help determine how advanced the airway widening is?
  2. 2.Can we review my file together to ensure we have completely ruled out CF, ABPA, and immune deficiencies?
  3. 3.Have my immunoglobulin levels (IgG, IgA, and IgM) been tested to see if my immune system is producing enough antibodies?
  4. 4.Based on my history of sinus or ear issues, should we consider testing for Primary Ciliary Dyskinesia (PCD)?
  5. 5.If my diagnosis remains idiopathic, what specific symptoms would prompt us to re-evaluate for an underlying cause in the future?

Questions For You

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References

References (17)
  1. 1

    Noncystic Fibrosis Bronchiectasis: Evaluation of an Extensive Diagnostic Protocol in Determining Pediatric Lung Disease Etiology.

    Beckeringh NI, Rutjes NW, van Schuppen J, Kuijpers TW

    Pediatric allergy, immunology, and pulmonology 2019; (32(4)):155-162 doi:10.1089/ped.2019.1030.

    PMID: 32140286
  2. 2

    A review of the etiology and clinical presentation of non-cystic fibrosis bronchiectasis: A tertiary care experience.

    Satırer O, Mete Yesil A, Emiralioglu N, et al.

    Respiratory medicine 2018; (137()):35-39 doi:10.1016/j.rmed.2018.02.013.

    PMID: 29605210
  3. 3

    Bronchiectasis evaluation 2025: pediatric and adult perspectives.

    Tolle J, O'Connor M

    Current opinion in pulmonary medicine 2025; (31(6)):622-627 doi:10.1097/MCP.0000000000001217.

    PMID: 40916968
  4. 4

    Pathogenesis, imaging and clinical characteristics of CF and non-CF bronchiectasis.

    Schäfer J, Griese M, Chandrasekaran R, et al.

    BMC pulmonary medicine 2018; (18(1)):79 doi:10.1186/s12890-018-0630-8.

    PMID: 29788954
  5. 5

    British Thoracic Society Guideline for bronchiectasis in adults.

    Hill AT, Sullivan AL, Chalmers JD, et al.

    Thorax 2019; (74(Suppl 1)):1-69 doi:10.1136/thoraxjnl-2018-212463.

    PMID: 30545985
  6. 6

    Refining diagnostic criteria for paediatric bronchiectasis using low-dose CT scan.

    Wu J, Bracken J, Lam A, et al.

    Respiratory medicine 2021; (187()):106547 doi:10.1016/j.rmed.2021.106547.

    PMID: 34340172
  7. 7

    Impact of bronchial wall thickness on airflow obstruction in bronchiectasis.

    Yamamoto Y, Kuge T, Miki K, et al.

    Respiratory physiology & neurobiology 2022; (295()):103788 doi:10.1016/j.resp.2021.103788.

    PMID: 34555525
  8. 8

    Management of bronchiectasis in adults.

    Visser SK, Bye P, Morgan L

    The Medical journal of Australia 2018; (209(4)):177-183 doi:10.5694/mja17.01195.

    PMID: 30107772
  9. 9

    Non-CF bronchiectasis: Orphan disease no longer.

    Imam JS, Duarte AG

    Respiratory medicine 2020; (166()):105940 doi:10.1016/j.rmed.2020.105940.

    PMID: 32250872
  10. 10

    Genome sequencing reveals underdiagnosis of primary ciliary dyskinesia in bronchiectasis.

    Shoemark A, Griffin H, Wheway G, et al.

    The European respiratory journal 2022; (60(5)) doi:10.1183/13993003.00176-2022.

    PMID: 35728977
  11. 11

    Immunological corollary of the pulmonary mycobiome in bronchiectasis: the CAMEB study.

    Mac Aogáin M, Chandrasekaran R, Lim AYH, et al.

    The European respiratory journal 2018; (52(1)) doi:10.1183/13993003.00766-2018.

    PMID: 29880655
  12. 12

    Prospective Study of <italic>Aspergillus</italic> IgG and Clinical Outcomes in Patients with Bronchiectasis.

    Yang J, Zhang K, Lu S, et al.

    Respiration; international review of thoracic diseases 2026; (105(3)):360-369 doi:10.1159/000548741.

    PMID: 41082454
  13. 13

    Why, when and how to investigate primary ciliary dyskinesia in adult patients with bronchiectasis.

    Contarini M, Shoemark A, Rademacher J, et al.

    Multidisciplinary respiratory medicine 2018; (13(Suppl 1)):26 doi:10.1186/s40248-018-0143-6.

    PMID: 30151188
  14. 14

    Computed tomography in adult patients with primary ciliary dyskinesia: Typical imaging findings.

    Dettmer S, Ringshausen F, Vogel-Claussen J, et al.

    PloS one 2018; (13(2)):e0191457 doi:10.1371/journal.pone.0191457.

    PMID: 29408869
  15. 15

    Etiology and characteristics of patients with bronchiectasis in Taiwan: a cohort study from 2002 to 2016.

    Huang HY, Chung FT, Lo CY, et al.

    BMC pulmonary medicine 2020; (20(1)):45 doi:10.1186/s12890-020-1080-7.

    PMID: 32070324
  16. 16

    The Bronchiectasis Severity Index and FACED score for assessment of the severity of bronchiectasis.

    Costa JC, Machado JN, Ferreira C, et al.

    Pulmonology 2018; (24(3)):149-154 doi:10.1016/j.rppnen.2017.08.009.

    PMID: 29306672
  17. 17

    Antibody deficiencies with normal IgG in adults with Non-cystic fibrosis bronchiectasis or recurrent pneumonia: Cross-sectional study.

    Zea-Vera AF, Chacón MA, Parra B

    Colombia medica (Cali, Colombia) 2022; (53(2)):e2014832 doi:10.25100/cm.v53i2.4832.

    PMID: 36415694

This page provides educational information about diagnosing idiopathic bronchiectasis. Always consult your pulmonologist to interpret your HRCT scans and specific laboratory results.

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