Thoracentesis drains fluid that has collected between the lung and the chest wall, called a pleural effusion. Cancers of the lung, breast and lymphatic system are among the causes. The fluid can press on the lung and cause breathlessness and cough.

Ultrasound identifies a safe site. The patient sits leaning forward, the skin is numbed, and a thin needle or catheter is passed between the ribs to drain the fluid. The amount drained is limited to avoid discomfort or a drop in blood pressure. The fluid is usually sent for testing, and a chest X-ray may be taken afterwards.

How the Procedure Can Help

It relieves breathlessness quickly and helps identify the cause of the fluid, including cancer cells.

Risks and Considerations

Cough, chest discomfort, and, less often, air leaks into the chest (pneumothorax), bleeding, or infection can occur. Fluid may return, and further treatments may be needed. Worsening breathlessness or chest pain afterwards needs urgent attention.