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PubMed This is a summary of 18 peer-reviewed journal articles Updated
Pulmonology

The Biology of Scarring and Your Diagnostic Reports

At a Glance

Idiopathic Pulmonary Fibrosis (IPF) is typically diagnosed using an HRCT scan to look for a specific scarring pattern called UIP, which often includes features like honeycombing. A multidisciplinary team of doctors can usually confirm the diagnosis without needing an invasive surgical lung biopsy.

To understand Idiopathic Pulmonary Fibrosis (IPF), it helps to look at the biology of what is happening inside your lungs and learn how to translate the complex language in your diagnostic reports. While the terms can seem overwhelming, they describe a specific process of “miscommunication” within your body.

The Biology: A Miscommunication

In a healthy lung, the body can repair minor injuries to the tiny air sacs (alveoli). In IPF, this repair process goes wrong due to a breakdown in communication between two types of cells: epithelial cells (the lining of the air sacs) and mesenchymal cells (the cells that help build tissue) [1].

  1. Chronic Injury: The lining of your lungs (epithelial cells) becomes chronically injured [1].
  2. TGF-beta1 Signal: These injured cells release a powerful protein called TGF-beta1 [2]. Think of this as a “danger signal” that never turns off.
  3. Myofibroblast Activation: The signal causes repair cells to turn into “active builders” called myofibroblasts [2].
  4. Fibroblastic Foci: These “builders” gather in small clusters called fibroblastic foci [3]. These are the active “front lines” of scarring, where the body creates excessive scar tissue that stiffens the lungs [1][3].

Auditing Your Imaging (HRCT) Report

The primary tool for diagnosing IPF is a High-Resolution Computed Tomography (HRCT) scan [4]. Your radiologist is looking for a specific appearance called a UIP pattern (Usual Interstitial Pneumonia) [5]. Here are the key terms you might see:

  • Subpleural/Basal Predominance: This means the scarring is mostly at the very bottom (basal) and outer edges (subpleural) of your lungs [6].
  • Reticular Abnormality: This looks like a fine, net-like pattern on the scan, representing the scar tissue [4].
  • Traction Bronchiectasis: This occurs when scar tissue pulls and stretches your airways (bronchi) open, making them look jagged or irregular [7].
  • Honeycombing: This is a hallmark of “Definite UIP.” It looks like tiny clusters of stacked air bubbles or a beehive [8]. It represents areas where the lung structure has been permanently altered [9].

The Diagnostic Gold Standard: MDD

In the past, many patients were sent for a surgical lung biopsy (removing a small piece of lung tissue) to confirm IPF. Today, this is often unnecessary [10].

The current “gold standard” for diagnosis is the Multidisciplinary Discussion (MDD) [11]. This is a formal meeting where a pulmonologist, a radiologist, and (if needed) a pathologist review your case together [12].

  • When a biopsy is unnecessary: If your HRCT shows a “Definite” or “Probable” UIP pattern and your clinical history matches, the MDD team can often confirm IPF without surgery [13][14].
  • When a biopsy is considered: If your scan is “Indeterminate” (not clearly one way or the other), the team may suggest a biopsy or a less invasive cryobiopsy to get more information [15][16].

By using an MDD, your care team can reach a high-confidence diagnosis while minimizing the risks associated with invasive procedures [17][18].

Common questions in this guide

What does a UIP pattern mean on my HRCT scan?
A UIP (Usual Interstitial Pneumonia) pattern is the specific visual appearance radiologists look for on an HRCT scan to diagnose IPF. It typically involves scarring at the bottom and outer edges of the lungs, along with features like honeycombing.
Is a surgical lung biopsy required to diagnose idiopathic pulmonary fibrosis?
In many cases, a surgical biopsy is no longer necessary. If your HRCT scan shows a definite or probable UIP pattern, a team of specialists can often confirm an IPF diagnosis without an invasive procedure.
What does 'honeycombing' mean on my lung radiology report?
Honeycombing on a lung scan looks like tiny clusters of stacked air bubbles or a beehive. It is a hallmark sign of definite UIP and indicates areas where the lung tissue has been permanently scarred and altered.
What is a Multidisciplinary Discussion (MDD) for pulmonary fibrosis?
An MDD, or Multidisciplinary Discussion, is a formal meeting where a pulmonologist, radiologist, and sometimes a pathologist review your medical history and scans together. It is considered the gold standard for reaching an accurate diagnosis.
What does traction bronchiectasis mean?
Traction bronchiectasis occurs when stiff scar tissue in the lungs pulls on your airways (bronchi), stretching them open and making them look irregular. This structural damage can contribute to the shortness of breath you experience.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Does my HRCT scan show a 'Definite,' 'Probable,' or 'Indeterminate' UIP pattern?
  2. 2.Given my HRCT results, do you think a surgical lung biopsy is truly necessary, or can we reach a diagnosis through a multidisciplinary discussion (MDD)?
  3. 3.If my report shows 'honeycombing,' what does that tell us about the current stage and expected progression of my condition?
  4. 4.How do the findings in my report, such as 'traction bronchiectasis,' correlate with the shortness of breath I am feeling?
  5. 5.Can we discuss the results of my MDD—who was involved (radiologist, pulmonologist, pathologist) and what was their consensus?

Questions For You

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References

References (18)
  1. 1

    Pathogenic Mechanisms Underlying Idiopathic Pulmonary Fibrosis.

    Moss BJ, Ryter SW, Rosas IO

    Annual review of pathology 2022; (17()):515-546 doi:10.1146/annurev-pathol-042320-030240.

    PMID: 34813355
  2. 2

    Targeted treatment of idiopathic pulmonary fibrosis: one step at a time.

    Richeldi L

    The European respiratory journal 2016; (47(5)):1321-3 doi:10.1183/13993003.00389-2016.

    PMID: 27132264
  3. 3

    SULF1 expression is increased and promotes fibrosis through the TGF-β1/SMAD pathway in idiopathic pulmonary fibrosis.

    Tu M, Lu C, Jia H, et al.

    Journal of translational medicine 2024; (22(1)):885 doi:10.1186/s12967-024-05698-3.

    PMID: 39354547
  4. 4

    Tissue Continues to Be the Issue: Role of Histopathology in the Context of Recent Updates in the Radiologic Classification of Interstitial Lung Diseases.

    Raparia K, Raj R

    Archives of pathology & laboratory medicine 2019; (143(1)):30-33 doi:10.5858/arpa.2018-0134-RA.

    PMID: 30785335
  5. 5

    Current State of Fibrotic Interstitial Lung Disease Imaging.

    Chelala L, Brixey AG, Hobbs SB, et al.

    Radiology 2025; (316(1)):e242531 doi:10.1148/radiol.242531.

    PMID: 40590695
  6. 6

    Smoking-related lung abnormalities on computed tomography images: comparison with pathological findings.

    Iwasawa T, Takemura T, Ogura T

    Japanese journal of radiology 2018; (36(3)):165-180 doi:10.1007/s11604-017-0713-0.

    PMID: 29247372
  7. 7

    Effect of Nintedanib in Subgroups of Idiopathic Pulmonary Fibrosis by Diagnostic Criteria.

    Raghu G, Wells AU, Nicholson AG, et al.

    American journal of respiratory and critical care medicine 2017; (195(1)):78-85 doi:10.1164/rccm.201602-0402OC.

    PMID: 27331880
  8. 8

    CT Findings, Radiologic-Pathologic Correlation, and Imaging Predictors of Survival for Patients With Interstitial Pneumonia With Autoimmune Features.

    Chung JH, Montner SM, Adegunsoye A, et al.

    AJR. American journal of roentgenology 2017; (208(6)):1229-1236 doi:10.2214/AJR.16.17121.

    PMID: 28350485
  9. 9

    Quantitative CT analysis of honeycombing area predicts mortality in idiopathic pulmonary fibrosis with definite usual interstitial pneumonia pattern: A retrospective cohort study.

    Nakagawa H, Ogawa E, Fukunaga K, et al.

    PloS one 2019; (14(3)):e0214278 doi:10.1371/journal.pone.0214278.

    PMID: 30897161
  10. 10

    Diagnosis of Idiopathic Pulmonary Fibrosis in a Possible Usual Interstitial Pneumonia Pattern: a meta-analysis.

    Kim H, Yoon SH, Hong H, et al.

    Scientific reports 2018; (8(1)):15886 doi:10.1038/s41598-018-34230-z.

    PMID: 30367143
  11. 11

    Implications of the diagnostic criteria of idiopathic pulmonary fibrosis in clinical practice: Analysis from the Australian Idiopathic Pulmonary Fibrosis Registry.

    Jo HE, Glaspole I, Goh N, et al.

    Respirology (Carlton, Vic.) 2019; (24(4)):361-368 doi:10.1111/resp.13427.

    PMID: 30328644
  12. 12

    Diagnostic Ability of a Dynamic Multidisciplinary Discussion in Interstitial Lung Diseases: A Retrospective Observational Study of 938 Cases.

    De Sadeleer LJ, Meert C, Yserbyt J, et al.

    Chest 2018; (153(6)):1416-1423 doi:10.1016/j.chest.2018.03.026.

    PMID: 29608882
  13. 13

    Guidelines of the Polish Respiratory Society for diagnosis and treatment of idiopathic pulmonary fibrosis.

    Piotrowski WJ, Bestry I, Białas AJ, et al.

    Advances in respiratory medicine 2020; (88(1)):41-93 doi:10.5603/ARM.2020.0081.

    PMID: 32153010
  14. 14

    Update on Interstitial Pneumonias.

    Carroll MB, Kanne JP, Martin Rother MD

    Clinics in chest medicine 2024; (45(2)):419-431 doi:10.1016/j.ccm.2023.08.015.

    PMID: 38816097
  15. 15

    Diagnosis of Idiopathic Pulmonary Fibrosis. An Official ATS/ERS/JRS/ALAT Clinical Practice Guideline.

    Raghu G, Remy-Jardin M, Myers JL, et al.

    American journal of respiratory and critical care medicine 2018; (198(5)):e44-e68 doi:10.1164/rccm.201807-1255ST.

    PMID: 30168753
  16. 16

    Applications of cryobiopsy in airway, pleural, and parenchymal disease.

    DeMaio A, Thiboutot J, Yarmus L

    Expert review of respiratory medicine 2022; (16(8)):875-886 doi:10.1080/17476348.2022.2122444.

    PMID: 36069255
  17. 17

    Utility of Flexible Bronchoscopic Cryobiopsy for Diagnosis of Diffuse Parenchymal Lung Diseases.

    Lentz RJ, Taylor TM, Kropski JA, et al.

    Journal of bronchology & interventional pulmonology 2018; (25(2)):88-96 doi:10.1097/LBR.0000000000000401.

    PMID: 28796717
  18. 18

    Diagnostic utility of surgical lung biopsies in elderly patients with indeterminate interstitial lung disease.

    Vaszar LT, Larsen BT, Swanson KL, et al.

    Respirology (Carlton, Vic.) 2018; (23(5)):507-511 doi:10.1111/resp.13223.

    PMID: 29178216

This page explains the biology and diagnostic terminology of Idiopathic Pulmonary Fibrosis for educational purposes only. Always discuss your specific HRCT results and diagnosis with your pulmonologist and healthcare team.

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