The purpose of this study is to evaluate the feasibility, size and quality of the specimens obtained by cryoprobe in comparison to those specimens obtained by flexible forceps during medical thoracoscopy in diagnosis of pleural effusion.

• Medical thoracoscopy with single-port-of-entry technique will be performed in the bronchoscopy unit under local anesthesia and conscious sedation using midazolam (2 mg) or pethidin.
• vertical incision will be made with the scalpel (usually near the midaxillary line), through the skin and subcutaneous tissue, appropriate to the size of the trocar to be used, usually of approximately 10 mm, parallel with and in the middle of the selected intercostal space.
• Then the trocar will be inserted until the sudden release of resistance (after passing the costal pleura) is felt.
• Under direct vision with the thoracoscope, introduction of pneumothorax will be performed, and all pleural fluid will be removed, and the pleural cavity will be inspected.
• Suspicious areas will be biopsied through the working channel of the thoracoscope.
• two to six biopsies of a suspicious pleural lesion will establish the diagnosis.

Technique of pleural biopsy using cryotechnique:

• The probe (ERBE Elektromedizin GmbH( Gesellschaft mit beschränkter Haftung) , Germany of 2.4mm) will be placed perpendicular to the surface of the parietal pleura with the tip of the probe extended well beyond the tip of the scope using the marking on the probe and with direct visualization.
• The tip of the cryoprobe will be attached to suspicious part of parietal pleura and activated by footswitch.
• carbon dioxide will be used as the cryogen gas for cryobiopsy
• The frozen tissue is going to be extracted by gently pulling of the probe.
• Freezing will be carried out for 6 to 10 seconds depending on the visual assessment of pleural texture.

Inclusion Criteria:

- 1. Unilateral moderate or massive exudative pleural effusion patients. 2. Undiagnosed pleural effusion after simple pleural fluid aspiration, cytology or blind (closed) pleural biopsy using Abram's needle.

3. Age>18 years old

Exclusion Criteria:

1. Transudative pleural effusion.

2. Exudative pleural effusion less than one third of hemithorax.

3. Presence of hemorrhagic diathesis (prothrombin concentration <50% and platelet count <80,000/mm 3).

4. Poor performance state (ECOG performance status >4) as recommended in BTS (British thoracic society) guidelines 2010.

5. Sever uncontrollable cough, hypercapnia and sever respiratory distress.

6. Fibrothorax, excessive pleural adhesion.

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