Fleischner 2017 pulmonary nodule calculator
Enter the long and short axis and the calculator applies the guideline mean diameter and rounding, then gives the Fleischner Society 2017 follow-up recommendation for an incidental lung nodule. Add the prior study to see the interval change against the 2 mm growth threshold. Copy a report line you can paste straight into your CT chest report.
Enter both axes to have the mean diameter averaged and rounded for you, or type the mean straight into the field.
Compare with the prior study
Optional. Leave blank for a newly detected nodule.
Report line
Fleischner Society 2017 follow-up recommendations
The guideline splits nodules by texture and size, and — for solid nodules — by whether the patient is low or high risk. Size is the mean diameter (average of the long and short axes). Approximate volume equivalents: <6 mm ≈ <100 mm³, 6–8 mm ≈ 100–250 mm³, >8 mm ≈ >250 mm³.
Measuring the nodule
Manual caliper size is the average of the long- and short-axis diameters, rounded to the nearest whole millimetre. The rounding matters at the band edges: a nodule measuring 8 × 5 mm averages 6.5 mm, reports as 7 mm and therefore sits in the 6–8 mm band rather than below 6 mm. Enter both axes above and the calculator applies that rule for you.
Comparing with the prior study
An increase of 2 mm or more in mean diameter counts as growth on manual measurement; smaller changes sit inside measurement variability and read as stable. Where CT volumetry is available, a volume increase of more than 25% is used instead, because volume changes earlier than diameter. A nodule that has grown is no longer a newly detected incidental nodule, so the follow-up table below stops applying and management is reassessed.
Solid nodules
| Size | Single, low risk | Single, high risk |
|---|---|---|
| <6 mm | No routine follow-up | Optional CT at 12 months |
| 6–8 mm | CT at 6–12 months, then consider CT at 18–24 months | CT at 6–12 months, then CT at 18–24 months |
| >8 mm | Consider CT at 3 months, PET-CT, or sampling | Consider CT at 3 months, PET-CT, or sampling |
For multiple solid nodules the first follow-up moves earlier to 3–6 months, and management is based on the most suspicious nodule.
Subsolid nodules (single)
| Size | Pure ground-glass | Part-solid |
|---|---|---|
| <6 mm | No routine follow-up (consider 2 & 4 yr if suspicious) | No routine follow-up |
| ≥6 mm | CT at 6–12 months to confirm persistence, then CT every 2 years to 5 years | CT at 3–6 months; if unchanged and solid component <6 mm, annual CT for 5 years |
A persistent part-solid nodule with a solid component of 6 mm or larger is highly suspicious. Multiple subsolid nodules are followed at 3–6 months, then by the most suspicious nodule.
Sources: MacMahon H, Naidich DP, Goo JM, et al. Guidelines for Management of Incidental Pulmonary Nodules Detected on CT Images: From the Fleischner Society 2017. Radiology 2017;284(1):228–243. Measurement and rounding follow Bankier AA, MacMahon H, Goo JM, et al. Recommendations for Measuring Pulmonary Nodules at CT: A Statement from the Fleischner Society. Radiology 2017;285(2):584–600.