Medical thoracoscopy (MT) under local anaesthetic and mild sedation, an established method in the diagnosis of pleural diseases. MT has an overall diagnostic yield above 90% for malignant pleural diseases and pleural tuberculosis. However, others who are diagnosed as fibrinous pleuritis make confusion in clinicians. Whether these patients are firmly followed or not ? The investigators do not know the answer of this question.

In this study the investigators aimed to investigate the outcome of the patients who are diagnosed as fibrinous pleuritis on MT biopsies.

Medical thoracoscopy (MT) under local anaesthetic and mild sedation, an established method in the diagnosis of pleural diseases with a sensitivity above 90% and specificity of 1000% for malignant pleural diseases and pleural tuberculosis. Except these two groups of patients, in others pleural histopathological diagnosis is defined as "non-specific pleuritis" or "fibrinous pleuritis". Authors say that the natural evolution of these patients is poorly understood. Some of these patients was later established false negative cases for malignant pleural diseases. Clinical guidelines recommend close observation of patients with undiagnosed exudative effusions, although the length and follow-up regime is not defined, yet. In this study the investigators examine the outcome of patients who are diagnosed as fibrinous pleuritis by MT.

Inclusion Criteria:

• Undiagnosed exudative pleural effusion
• Under 20 years-old, over 85 years-old
• Followed 2 years at least

Exclusion Criteria:

• Transudative pleural effusion
• Patients who do not accepted medical thoracoscopy.

The patients with undiagnosed exudative pelural effusion by clinical, radiological or laboratory investigations.