Having a pleural effusion is a common reason for being hospitalized, as it usually requires in-patient care for invasive diagnostic and therapeutic procedures. Specific subtypes of pleural effusion may warrant recurrent admissions, a longer hospital stay and consume more healthcare resources. Despite the recent advancement of pleural medicine, better research is increasingly desired to fill the gaps in establishing an early diagnosis and optimal management of pleural effusion from various causes. Local data on different aspects of pleural effusion is also lacking.

The aetiologies of pleural effusion range from cardio-respiratory diseases, malignancy, infection to systemic inflammatory conditions. However, data on the exact incidence of individual causes of pleural effusion is inadequate. Conflicting results on the aetiologies of pleural effusion were shown in several retrospective and prospective studies based in different geographical regions, which may be explained by the different epidemiology of common diseases in the corresponding areas and patients recruited. Despite a common clinical problem, the incidence and aetiology of pleural effusion have not been examined on a population level in Hong Kong. Therefore, a local study is necessary to inform physicians about the disease burden of pleural effusion.

The management of pleural disease can be heterogeneous, as reflected by a recent multi-institutional questionnaire study in Hong Kong. Infrequent updates of international guidelines of pleural medicine, lack of an established registry reflecting the patient burden, procedure load and complications may contribute. Delayed or suboptimal management of pleural diseases can lead to unnecessary invasive procedures, prolonged hospital stays and even higher mortality rates. A local registry should be established to stocktake and understand diagnostic accuracy and complication rates of pleural procedures and reflects the real-life practice by hospital physicians.

This prospective study aims at evaluating the aetiology and management of pleural diseases prospectively. The management by the attending doctors will not be interfered. Recruited patients will be divided into subgroups based on their characteristics for further analysis. The data collected from this study will guide the planning of subsequent research to overcome the knowledge and service gap in managing pleural diseases.

Inclusion Criteria:

• Patients hospitalized for pleural effusion.
• Pleural tapping will be performed for pleural fluid analysis.
• Aged 18 years old or above

Exclusion Criteria:

- Failed to obtain informed consent due to the patient's refusal or cognitive impairment

Patients who have pleural effusion and will undergo thoracentesis for pleural fluid sampling