Introduction: The prevalence of incidental lung cysts is not known. We set out to establish this via a retrospective analysis of chest CTs.

Objectives: Unlike other solid organs, cysts in lungs are often pathological and multiple lung cysts require diagnostic work up. CT chest to diagnose and screen for causes of breathlessness, or lung cancer, has potential to identify other less common lung pathology, including cystic lung disease. Our study shows that incidental lung cysts are not uncommon and potentially present a large unmet need.

Methods: All chest CT scans, performed for any indication, held on the radiology database in a single hospital Trust over a two-year period (January 2018 to December 2020) had their report searched for the word ?cyst?. Scans were further analysed for demographics, number of cysts and follow up under Respiratory service or specialist cystic lung centre (SCLC) using clinic codes. Cysts outside the lungs were excluded.

Results: A total of 76,212 CT scan reports were searched with lung cysts reported in 228 scans. 54 of 228 were excluded due to absence of true cysts, non-availability of hospital identification number or duplication, leaving 174 scans giving a prevalence of lung cysts in 0.23% of CT scans. Mean age was 64 years. 45% were females. 27% of scans reported solitary cysts; 73% reported multiple (>3) cysts. 57% (100/174) of patients with lung cysts were not known to Respiratory Service. Only 16% (21/127) of multiple lung cysts were known to the SCLC. (Figure 1)

Conclusion: Our data and methodology suggest that incidental lung cysts can be identified and followed up using simple analysis of radiology databases allowing future prognostic and biomarker studies.