Pleuroscopy in 'Idiopathic' eosinophilic pleural effusions

Background: Idiopathic eosinophilic pleural effusions (IEPEs) comprise the eosinophilic pleural effusions for which a specific aetiology cannot be established. There are no reports investigating IEPE on the basis of a systematically applied pleuroscopy approach and entailing an appropriate patient follow-up till the final outcome is established; existing series rather combine clinical and thoracocentesis criteria to establish the idiopathic character of the diagnosis.

Objectives: The aim of our study was to assess the clinical outcome of patients with IEPE, who underwent a systematic diagnostic approach by pleuroscopy.

Methods: We studied 10 patients with IEPE among 175 consecutive patients who underwent pleuroscopy for undiagnosed pleural effusion. Pleural biopsies were obtained from observed lesions. All patients were followed up by means of clinical examination and imaging.

Results: The diagnosis of IEPE was established in 10 patients (median age was 50.5 years, range 35-91). Macroscopic examination of the pleura showed diffuse thickening with pleural plaques in eight patients, consistent with diffuse pleural eosinophilic inflammation histologically proven. In two patients, macroscopic examination showed scattered nodules associated with non-caseating granulomas histologically. In all 10 patients, a specific aetiology could not be established. Follow-up was available for all patients ranging from 24-102 months (median 60 months). No patient received a specific treatment during the follow-up period. No relapse of a pleural effusion was documented during this period.

Conclusion: Pleuroscopy is mandatory in diagnosing IEPE. Negative histology and a long follow-up showed a benign course. These findings suggest that we should call these effusions 'indeterminate'.