What is the appropriate next management and follow‑up plan for a patient with a stable 3.7 mm right‑transverse‑fissure pulmonary nodule, a left‑lower‑lobe subpleural nodule now replaced by focal interstitial thickening, bilateral apical fibrotic changes with mild pleural thickening, scattered ground‑glass opacities, interstitial coarsening, and bilateral lower‑lobe atelectasis?

Management of Pulmonary Nodules and Interstitial Changes

Right Transverse Fissure Nodule (3.7 mm, stable)

For this stable 3.7 mm solid nodule, no further follow-up imaging is required. 1, 2

• Solid nodules <5 mm in diameter do not require routine surveillance imaging because the malignancy risk is well below 1%, even in high-risk patients 3
• The nodule has shown minimal change (3.3 mm to 3.7 mm), which falls within measurement variability and does not constitute true growth 1
• The American College of Radiology specifically states that nodules <6 mm in low-risk patients need not be followed 1, 2
• Research confirms that nodules ≤4 mm have a calculated growth probability of <1.28% within 12 months, making short-term follow-up unnecessary 4

If you choose to perform optional surveillance (based on patient anxiety or upper lobe location), a single follow-up CT at 12 months would be the maximum reasonable approach 1, 3

Left Lower Lobe Subpleural Nodule (Now Focal Interstitial Thickening)

The resolution of the 30 mm subpleural nodule into focal interstitial thickening strongly suggests a benign process, most likely focal interstitial fibrosis or organizing pneumonia. 5

• Focal interstitial fibrosis commonly manifests as nodular ground-glass opacity that evolves into interstitial thickening on follow-up imaging 5
• This pattern of resolution argues against malignancy, which would typically persist or progress rather than resolve into linear fibrosis 5
• No further imaging or biopsy is indicated for this resolved lesion unless new symptoms develop 5

Bilateral Apical Fibrotic Changes and Scattered Ground-Glass Opacities

These findings require clinical correlation to determine if they represent interstitial lung abnormality (ILA) versus established interstitial lung disease (ILD). 6

Immediate Clinical Assessment Required:

• Obtain detailed smoking history (pack-years, current vs. former smoker) to assess for respiratory bronchiolitis-associated ILD, which presents with ground-glass opacities and interstitial coarsening in smokers 7
• Perform pulmonary function tests (spirometry, lung volumes, DLCO) to determine if physiologic impairment is present 6
• Assess for respiratory symptoms: dyspnea on exertion, chronic cough, or exercise limitation attributable to these findings 6, 7
• Review occupational and environmental exposures: asbestos, silica, birds, mold, hypersensitivity pneumonitis triggers 6
• Screen for connective tissue disease: joint symptoms, Raynaud's phenomenon, skin changes, dry eyes/mouth 6

Classification Algorithm:

If patient is asymptomatic AND PFTs are normal:

• Classify as ILA (interstitial lung abnormality) 6
• Perform reactive monitoring: repeat high-resolution CT only if symptoms develop 6
• No routine surveillance imaging is needed 6

If patient has mild symptoms OR borderline PFT abnormalities:

• Classify as high risk for ILD 6
• Perform proactive monitoring: repeat high-resolution CT in 6-12 months to assess for progression 6
• Consider referral to pulmonology for multidisciplinary discussion 1

If patient has significant symptoms AND abnormal PFTs attributable to imaging findings:

• Classify as probable ILD or ILD 6
• Immediate referral to ILD specialist/pulmonology is mandatory 1, 6
• Consider bronchoscopy with transbronchial biopsy or surgical lung biopsy if diagnosis remains uncertain after multidisciplinary discussion 6

High-Resolution CT Technical Requirements for Follow-Up:

• Use thin-section (1.0-1.5 mm) non-contrast technique 1, 8
• Employ low-dose protocol to minimize cumulative radiation exposure 1, 8
• Obtain prone images to distinguish dependent atelectasis from true fibrosis 6

Bilateral Lower Lobe Atelectasis

This finding is likely positional/dependent and requires no specific intervention unless associated with symptoms. 6

• Repeat imaging in the prone position can confirm this is dependent atelectasis rather than true parenchymal disease 6
• If atelectasis persists on prone imaging or is associated with volume loss, consider bronchoscopy to exclude endobronchial obstruction (only if clinically indicated) 6

Critical Pitfalls to Avoid:

• Do not perform PET/CT for the 3.7 mm nodule—it is too small for reliable PET assessment (requires >8 mm) 1, 2, 3
• Do not biopsy the small right-sided nodule—procedural risks far outweigh diagnostic benefit for nodules <6 mm 3
• Do not use chest radiography for nodule surveillance—it lacks sensitivity for lesions <1 cm 8, 3
• Do not assume ground-glass opacities are malignant—in smokers, respiratory bronchiolitis-associated ILD is a common benign cause 7
• Do not delay ILD referral if the patient has progressive dyspnea and abnormal PFTs—early antifibrotic therapy may be indicated for progressive fibrotic phenotype 1

Summary Action Plan:

1. Discharge the patient from nodule surveillance for the 3.7 mm right-sided nodule 1, 2, 3
2. Perform PFTs and detailed clinical assessment to classify the interstitial changes 6
3. If asymptomatic with normal PFTs: reactive monitoring only (no routine imaging) 6
4. If symptomatic or abnormal PFTs: refer to pulmonology and obtain follow-up high-resolution CT in 6-12 months 1, 6