Percutaneous drainage, thoracic

A pleural effusion should be drained when it is large enough to cause symptoms (usually breathlessness) or when it is likely to loculate or cause pleural fibrosis (particularly infected effusion and haemothorax). A coagulation defect and local skin infection are relative contraindications. Percutaneous drainage of a chest collection may be performed with or without image guidance, in the former case, using either ultrasound or CT (Fig.1) and less frequently fluoroscopy. Image guidance precisely demonstrates the effusion and its relation to the underlying lung and diaphragm, establishes whether it is loculated and helps determine the best site for drainage. Using imaging guidance, chest drainage tubes may be placed accurately even within small, loculated collections. Pigtail catheters varying in size between 8F and 20F are used, with 12 - 14F being suitable for most collections apart from haemothoraces. Whilst patients tolerate catheters better than large bore tubes they may obstruct unless flushed regularly with normal saline.

Chest ultrasonography and CT are complimentary imaging techniques. Ultrasound has the advantage of being less expensive than CT and it can be performed at the bedside. Ultrasound also demonstrates septa within the effusion better than CT. However, ultrasound is limited by the presence of air or calcification whilst CT both provides a more comprehensive overview of the pleura, lung and mediastinum and allows more precise placement of drainage tubes than ultrasound.

Once the collection has been demonstrated and the route of access defined, the skin is cleaned and local anaesthetic infiltrated just above the rib down to the pleura. A small amount of fluid should then be aspirated and sent for pathological assessment. The size of drainage tube selected depends on the gross appearance of the fluid. The aspirating needle is exchanged for a cannula with bore large enough to allow passage of a J-wire. The tube should be firmly attached to the skin and its end attached to an underwater seal. The drain should be kept on continuous suction of about 20 cm of water and regularly flushed with normal saline. It should remain in place until fluid drainage has ceased or is minimal (less than 100ml in 24 hours). Fibrinolytic agents improve drainage of empyemas and loculated collections. Either streptokinase or urokinase is injected into the pleural space via the chest tube. Streptokinase is given in a dose of 250,000 units daily for up to 5 days (see empyema).

Mediastinal fluid collection and lung abscess can also be drained percutaneously using CT guidance and catheters introduced in the same fashion as for pleural effusions. In both cases care should be taken to avoid transgressing the lung with the catheter. Also, see lung abscess, and acute mediastinitis.

CF - HM