Lung scarring seen by chance on a chest CT
A CT scan of the chest or upper belly, or a lung screening CT, can show small areas of haziness or scarring in the lungs that nobody was looking for. Radiologists call these interstitial lung abnormalities (ILAs). They are more common with age and are seen more often as more CT scans are done. (Fleischner 2020) This page covers what the finding means and what usually comes next, not treatment.
What the report means
The Fleischner Society, a group of chest imaging and lung specialists, defines ILAs as changes found by chance in someone not suspected of lung disease: hazy (ground-glass) or net-like (reticular) areas, lung distortion, widened airways pulled open by scarring (traction bronchiectasis), honeycombing or cysts, covering at least 5% of a lung zone. (Fleischner 2020)
Some findings are not ILAs on their own: collapsed areas at the back of the lungs from lying down, a small scar next to a spine bone spur, small smoking-related spots, a mild patch on one side, fluid from heart failure, or signs of inhaled food or liquid. (Fleischner 2020)
The three types on a report
| Type | What it looks like | What studies show |
|---|---|---|
| Non-subpleural | Changes not mainly at the outer edge of the lung | Usually do not progress and are not linked to higher mortality |
| Subpleural non-fibrotic | Changes mainly at the outer edge, no signs of scarring | Can progress; basal and outer changes count as a risk factor |
| Subpleural fibrotic | Changes at the outer edge with scarring (distortion, traction bronchiectasis or honeycombing) | More likely to progress and linked to higher mortality |
Source: (Fleischner 2020) If scarring is present, the pattern can be graded further with the 2018 ATS/ERS/JRS/ALAT and Fleischner criteria, as cited in the position paper. (Fleischner 2020) The report should name the type, because it helps predict progression. (Fleischner 2020)(Hata 2021)
How common it is with age
- In large studies of people over 60, ILAs were found in 4 to 9% of people who smoke and 2 to 7% of people who do not. (Fleischner 2020)
- Across 9 population and lung screening studies, the share with ILAs ranged from 3% to 17%, with average ages of 60 to 78. (Fleischner 2020)
- Older age is strongly linked to ILAs: in one study of people who smoke, each 10 more years of age raised the odds about 2.2 times. Smoking, other inhaled exposures and some genes are also risk factors. (Fleischner 2020)(Hata 2021)
- Where it was measured, the changes progressed on later scans in 20% to 63% of people over 2 to 6 years, and people with ILAs had a higher risk of death (hazard ratios 1.3 to 2.7). (Fleischner 2020)(Hata 2021)
What usually comes next
The Fleischner Society says evidence for a set plan is limited, and offers a proposal based on studies and expert opinion. (Fleischner 2020)
- A check for causes and symptoms. Your doctor asks about smoking and other inhaled exposures, medicines, conditions such as connective tissue disease, and repeated inhaling of food or stomach contents. (Fleischner 2020)
- A lung specialist for people with breathing symptoms or signs, abnormal breathing tests, or changes in 3 or more of the 6 lung zones. These may already be interstitial lung disease rather than ILAs. (Fleischner 2020)
- Follow-up for people at higher risk (for example smoking, other inhaled exposures, some cancer treatments, chest surgery, borderline breathing tests, or outer and lower changes with or without scarring): a first check at 3 to 12 months, which may include breathing tests, and possibly a repeat CT at 12 to 24 months. (Fleischner 2020)
- No set follow-up for people without risk factors. They should come back if breathing symptoms start. Non-subpleural changes alone seldom progress. (Fleischner 2020)
MedlinePlus lists the medical history, imaging tests, lung function tests and sometimes a biopsy as ways doctors diagnose pulmonary fibrosis. (MedlinePlus) The same scan may show other findings with their own pages: a lung nodule or emphysema.
If it was seen on a lung screening CT
The USPSTF recommends a yearly low-dose CT for adults 50 to 80 with a 20 pack-year smoking history who still smoke or quit within the past 15 years (grade B). (USPSTF 2021) ILAs are not part of those criteria. A 2021 review suggests radiologists list ILAs under the "significant other findings" note of the lung screening score (Lung-RADS). (Hata 2021) See lung cancer screening results and lung cancer screening.
Who it applies to
Adults told a CT shows ILAs or early scarring when no lung disease was suspected. The NHS says idiopathic pulmonary fibrosis mainly affects people 70 or over, and risk may be higher with long-term dust exposure (such as metal, wood or asbestos) or a close relative who had it. (NHS) If a CT was done because of known lung disease or a screening program for people at high risk, such as rheumatoid arthritis, scleroderma or a family history, those changes are not called ILAs. (Fleischner 2020)
NHS, when to get medical help for possible idiopathic pulmonary fibrosis: (NHS)
See a GP if:
- you think you might have idiopathic pulmonary fibrosis (IPF)
- you have shortness of breath that gets worse when you've been doing your normal activities, or when you lie down
- you've had a cough for 3 weeks or more
Routine age-based screening
A finding on a CT does not replace the routine screenings for your age. See screenings by age and gender.
Where they differ:
- Who starts the work-up. The Fleischner Society covers changes found by chance in people without suspected lung disease. (Fleischner 2020) The NHS describes tests (spirometry, a chest X-ray, then a CT) for people a doctor already suspects have pulmonary fibrosis because of symptoms. (NHS)
- Age. Fleischner prevalence figures are for people over 60. (Fleischner 2020) The NHS says idiopathic pulmonary fibrosis mainly affects people 70 or over. (NHS)
- Timing of follow-up. The Fleischner Society gives ranges (3 to 12 months, CT at 12 to 24 months) and says the best interval is unknown. (Fleischner 2020) The 2021 review says systematic follow-up including CT should be considered for the higher-risk group. (Hata 2021)
Your doctor decides what your result means for you.
Questions people ask
Does lung scarring on my CT mean I have lung fibrosis?
Not necessarily. The Fleischner Society uses the term interstitial lung abnormalities for changes found by chance in people not suspected of lung disease. Your doctor checks for symptoms and lung function to tell these apart from interstitial lung disease. (Fleischner 2020)
How common is it?
In studies of people over 60, the Fleischner Society reports these changes in 4 to 9% of people who smoke and 2 to 7% of people who do not. They become more common with age. (Fleischner 2020) (Hata 2021)
Will I need another scan?
It depends on the type and your risk factors. The Fleischner Society suggests a first check at 3 to 12 months for people at higher risk, and possibly a CT at 12 to 24 months; people without risk factors are told to come back if breathing symptoms start. Your doctor decides. (Fleischner 2020)
Does it change my lung cancer screening?
The USPSTF criteria for yearly lung screening are age 50 to 80, a 20 pack-year smoking history, and still smoking or having quit within 15 years. Interstitial lung abnormalities are not part of those criteria. (USPSTF 2021)
What symptoms should I tell a doctor about?
The NHS says to see a GP for breathlessness that gets worse with normal activities or lying down, or a cough for 3 weeks or more. (NHS)
Related
- Pleural plaques seen by chance on a chest scan
- Breast spot seen by chance on a chest CT
- Lung nodule found by chance: follow-up scans
- Emphysema found by chance on CT: what comes next
- Lung cancer screening results: Lung-RADS
- Low-dose CT lung scan: what to expect
- Spirometry and COPD screening: FEV1, FVC and the ratio
- After an abnormal screening result
- Screenings by age and gender