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. It checks whether the guideline applies, sets the risk column from the high-risk features you tick, and handles typical perifissural nodules. 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. To turn two volumes and the scan interval into a growth rate, use the volume doubling time calculator.
When Fleischner does not apply
The 2017 recommendations cover incidental nodules in adults aged 35 or older. They do not cover lung-cancer screening CT, which follows the screening programme's own protocol, such as ACR Lung-RADS or, in Australia, the National Lung Cancer Screening Program protocol. They do not cover patients with a known primary cancer at risk of metastases, or immunocompromised patients at risk of infection; management there follows the clinical situation. Under 35, lung cancer is rare, infection is more likely, and serial CT is kept to a minimum. Tick any of these above and the calculator gives that direction instead of an interval.
Choosing low or high risk
Risk changes the interval for solid nodules only. Fleischner 2017 uses the American College of Chest Physicians groups and combines intermediate and high risk into one high-risk column. Low risk means an estimated cancer risk below 5%: younger age, less smoking, a small nodule with regular margins, outside the upper lobe. Heavy smoking (the statement treats the NLST threshold of 30 or more pack-years, current or quit within 15 years, as high risk), asbestos, radon or uranium exposure, a family history of lung cancer, emphysema, pulmonary fibrosis, an upper-lobe location and an irregular or spiculated margin all raise risk. Because intermediate risk counts as high, the calculator uses the high-risk column when you tick any of these, and names them in the report line.
Perifissural nodules
Small solid nodules next to a fissure or other pleural surface are often intrapulmonary lymph nodes. Typical ones are triangular or oval on transverse images, flat or lentiform on sagittal or coronal images, and have a fine linear septal extension to the pleura. With that morphology, Fleischner 2017 does not recommend follow-up CT, even when the mean diameter exceeds 6 mm. Location alone is not enough: a spiculated border, a displaced fissure or a history of cancer raises the chance of malignancy, and CT at 6–12 months should then be considered. The statement gives no upper size limit for "small", so the calculator applies the rule up to 8 mm and gives the size-band advice above that.
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.