Fleischner nodule follow-up
Apply the Fleischner Society 2017 recommendations to an incidentally detected pulmonary nodule: type, number, size and risk profile give the follow-up interval.
Nodule
Recommendation
CT at 6–12 months, then consider CT at 18–24 months.
7 mm · solid · single
CT at 6–12 months, then consider CT at 18–24 months.
In this band the risk profile genuinely matters: at high risk the second follow-up is not a consideration but part of the recommendation. High risk includes a heavy smoking history, upper lobe location, a spiculated appearance and asbestos exposure.
The guideline applies to incidentally detected nodules in adults aged 35 and over. It does not apply in lung cancer screening, with a known malignancy, or in immunocompromised patients — those settings have their own, shorter schedules.
How to read the result
The output is an interval, not a diagnosis. A recommendation of no follow-up means the nodule carries a risk low enough that surveillance would harm more than help, which is a finding worth stating explicitly.
How the recommendation is built
Type × number × size × risk profile → one interval
Size is the average of the long and short axis on the same image, rounded to whole millimetres. Solid nodules split at 6 and 8 mm, subsolid nodules only at 6 mm.
High risk covers a heavy smoking history, upper lobe location, spiculated margins, emphysema or fibrosis, older age and asbestos exposure.
With multiple nodules, the most suspicious one drives management, not the largest.
When to use it
- Reporting an incidentally found pulmonary nodule on a CT performed for another reason.
- Deciding the follow-up interval that belongs in the conclusion rather than a vague suggestion to repeat imaging.
- Distinguishing a solid from a subsolid nodule, where the pathways diverge sharply.
- Checking whether a nodule needs no follow-up at all, which is the correct answer more often than reports suggest.
⚠️ Pitfalls
- The guideline does not apply in lung cancer screening, in patients with a known malignancy, in immunocompromised patients, or under the age of 35. Applying it there gives intervals that are too long.
- A perifissural or clearly benign calcified nodule needs no follow-up at all, whatever the size band suggests.
- Measure the average of long and short axis. Reporting only the long axis systematically pushes nodules into a higher band and generates surveillance nobody needed.
- A part-solid nodule is graded on its total size and its solid component separately. A growing solid component matters more than a stable total diameter.
- Comparison with prior imaging outranks the entire table. A nodule unchanged over two years usually needs nothing.
Frequently asked questions
What are the Fleischner 2017 criteria?
They are recommendations for following incidentally detected pulmonary nodules on CT in adults aged 35 and over, based on nodule type, number, size and the patient's risk profile.
Does a nodule under 6 mm need follow-up?
A solid nodule under 6 mm needs no routine follow-up at low risk, and only optional CT at 12 months at high risk. Under 6 mm, a single subsolid nodule also needs no routine follow-up.
How should the nodule be measured?
As the average of the long and short axis on the same image, rounded to whole millimetres. Using the long axis alone inflates the size band.
What counts as a high-risk patient?
A heavy smoking history, older age, upper lobe location, spiculated margins, emphysema or fibrosis, and asbestos exposure all push a patient into the higher-risk group.
Which nodule do I follow when there are several?
The most suspicious one, not the largest. Name it and give its location in the report, so the next reader measures the same nodule.
References
📄MacMahon H, et al. Guidelines for Management of Incidental Pulmonary Nodules Detected on CT Images: From the Fleischner Society 2017. Radiology. 2017;284(1):228–243.
📄Bankier AA, et al. Recommendations for Measuring Pulmonary Nodules at CT: A Statement from the Fleischner Society. Radiology. 2017;285(2):584–600.
This calculator supports clinical judgement and does not replace it. Always check the result against your own measurements and the guideline in force.
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