Use thin sections
Obtain contiguous thin-section CT—1.5 mm or less—and use multiplanar reconstructions to distinguish small nodules from linear opacities.
Incidental pulmonary nodule assistant
Fleischner Guidelines Calculator
Review 2017 Fleischner Society follow-up recommendations for incidental solid, ground-glass, and part-solid pulmonary nodules—with eligibility exclusions checked first.
Applicability guardrailsExact 6 and 8 mm thresholdsEvidence reviewed August 2026
Educational clinical decision support. This assistant summarizes published population guidance. It does not interpret the CT, estimate malignancy probability, diagnose cancer, or replace radiology and pulmonary judgment.
Applicability-first pathway
Find the appropriate incidental-nodule pathway
Enter the average CT diameter (long plus short axis divided by two, rounded to the nearest millimeter). For multiple nodules, characterize the most suspicious nodule.
Step 1 · Applicability
Confirm this is an eligible incidental finding
Detection context
Step 2 · CT phenotype
Describe the nodule pattern
Number of nodules
Nodule morphology
Clinical risk tier
The guideline does not provide a validated point score. Choose the tier using clinical judgment and local practice.
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Fleischner 2017 at a glance
Pulmonary nodule follow-up tables
These compact tables are reference summaries, not substitutes for the applicability screen, morphology review, prior-image comparison, or full guideline text.
| Solid pattern | Size | Lower risk | Higher risk |
|---|---|---|---|
| Single | <6 mm | No routine follow-up | Optional CT at 12 mo |
| Single | 6–8 mm | CT 6–12 mo; consider 18–24 mo | CT 6–12 and 18–24 mo |
| Single | >8 mm | Consider CT ~3 mo, PET/CT, or tissue sampling | Consider CT ~3 mo, PET/CT, or tissue sampling |
| Multiple | <6 mm | No routine follow-up | Optional CT at 12 mo |
| Multiple | ≥6 mm | CT 3–6 mo; consider 18–24 mo | CT 3–6 and 18–24 mo |
| Subsolid pattern | Size | Published follow-up |
|---|---|---|
| Single pure ground-glass | <6 mm | No routine follow-up; selected cases may consider CT at 2 and 4 y |
| Single pure ground-glass | ≥6 mm | CT 6–12 mo, then every 2 y until 5 y |
| Single part-solid | <6 mm | No routine follow-up |
| Single part-solid | ≥6 mm, solid part <6 mm | CT 3–6 mo, then annual CT for 5 y |
| Multiple subsolid | <6 mm | CT 3–6 mo; if stable, consider CT at 2 and 4 y |
| Multiple subsolid | ≥6 mm | CT 3–6 mo; manage by most suspicious nodule |
Average two axes
Measure long and short axes on the plane where the nodule is largest, calculate the average, and round to the nearest whole millimeter.
Measure the solid part
For part-solid nodules, record the total nodule and solid-component diameters. A change of at least 2 mm is considered meaningful growth.
Know when to stop
When Fleischner guidance does not apply
Age under 35
Use case-by-case management and minimize serial CT.
Lung cancer screening
Use the current ACR Lung-RADS or screening-program protocol.
Known primary cancer
Use individualized oncologic and multidisciplinary assessment.
Immunocompromised patient
Infectious and other etiologies require individualized timing.
Frequently asked questions
Fleischner criteria and lung nodule follow-up
Who should use the Fleischner guidelines?
The tables apply to incidental pulmonary nodules detected on CT in adults age 35 years and older. They exclude lung cancer screening examinations, immunocompromised patients, and patients with a known primary cancer.
What is the follow-up for a 6 mm solid pulmonary nodule?
Exactly 6 mm enters the 6–8 mm category. A single lower-risk nodule receives CT at 6–12 months and possible CT at 18–24 months; a higher-risk nodule receives CT at 6–12 and 18–24 months.
Does an 8 mm nodule enter the greater-than-8-mm pathway?
No. Exactly 8 mm remains in the 6–8 mm category. The CT/PET-CT/tissue-sampling pathway begins when the average diameter is greater than 8 mm.
What is the follow-up for a ground-glass nodule?
A single pure ground-glass nodule 6 mm or larger receives CT at 6–12 months to confirm persistence, then CT every 2 years until 5 years if persistent and unchanged.
Why does a part-solid nodule need the solid component measured?
The size and growth of the solid component strongly influence concern. A persistent part-solid nodule with a solid component 6 mm or larger is considered highly suspicious and generally leaves routine surveillance for diagnostic evaluation.
Do these guidelines apply to a nodule found on screening CT?
No. Use the current lung cancer screening framework, typically ACR Lung-RADS in the United States.
How do I choose lower versus higher risk?
The guideline uses clinical judgment rather than a point score. Older age, heavy smoking, larger size, spiculation, upper-lobe location, emphysema, and fibrosis increase risk; younger age, less smoking, regular margins, and non-upper-lobe location lower risk.
Should prior imaging be reviewed?
Yes. Prior CT or chest imaging can establish stability or growth and may materially change management. The published recommendation specifically emphasizes reviewing all available prior examinations.
Evidence base
Primary guidelines and reference material
Evidence and source availability reviewed August 16, 2026. The guideline year is stated explicitly because the Fleischner tables were published in 2017 and should not be presented as a newly issued 2026 guideline.
MacMahon et al. Guidelines for Management of Incidental Pulmonary Nodules (Fleischner Society, 2017)The official Fleischner Society recommendations and tables for incidentally detected solid and subsolid nodules in adults.Bankier et al. Recommendations for Measuring Pulmonary Nodules at CT (Fleischner Society, 2017)Consensus recommendations for linear and volumetric nodule measurement and reporting.Fleischner Society: Glossary of Terms for Thoracic Imaging (2024)Current standardized thoracic imaging terminology, including definitions for nodules and subsolid morphology.American College of Radiology Lung-RADSThe appropriate reporting and management framework for nodules detected in lung cancer screening programs.
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