Adrian Harrison - Respiratory Physician
What is a pleural effusion?
The pleural space was explained earlier, near the end of the section entitled, 'The Respiratory System'. There is normally a small amount of fluid (pleural fluid) in the pleural space. It drains away through the fine lymphatic vessels which empty into the blood stream. A large volume of pleural fluid is called a pleural effusion. It can accumulate if:
- The lymphatic drainage of the pleural space is blocked - for example by cancer or lymphoma in the lymph nodes, or by scar tissue in the centre of the chest (i.e. the mediastinum) OR
- The pleural surface is irritated or inflamed - for example, by infection or cancer OR
- The fluidic partial pressure in the pleural space is lower than that in the bloodstream - for instance, when the heart fails to pump effectively or the kidneys cannot excrete enough fluid, because of disease in either of these organs.
- Bleeding into the pleural space because of trauma or after a chest operation can also result in excessive fluid - in this case blood - in the pleural space.
A large pleural effusion usually causes breathlessness which gets worse as the volume of fluid increases.
Pleural aspiration and pleural biopsy
These procedures can be done in different ways. A surgeon can perform them, usually thoracoscopically (i.e. 'key hole' surgery in which thin, rigid telescopes to which biopsy forceps or other instruments can be attached, are inserted through the chest wall). Thoracoscopy requires a general anaesthetic and one or more days in hospital.
I (and other chest physicians) perform these procedures under local anaesthetic and sedation, using a special needle which is much finer than the instruments a surgeon uses. Afterwards the patient has a chest X-ray and then returns home.
The best site for inserting the special needle is located beforehand by ultrasound (i.e. bouncing sound waves through the chest wall), confirming there is fluid at that site. I put local anaesthetic under the skin and then into the muscle at that site, before inserting the needle through which biopsies and fluid can be collected.
The procedure can take anything from 20 - 60 minutes, depending on how much fluid has to be removed. I close the aspiration and biopsy site with a suture (i.e. a stitch) that needs to be removed about 5 days later by your GP.
Is pleural aspiration or pleural biopsy painful?
This depends to a large extent on the skill of the person doing the procedure. Performed by an expert, they should be pain-free or almost pain-free. That is always my aim. And if there is discomfort I will always do my best to minimise it.
Care is needed with very large pleural effusions (e.g. where there is more than 1.5 litres of fluid) or the effusion has been present for a long time. Rapid removal of fluid can cause pain or make breathing worse. In these situations it is sometimes better to insert a pleural catheter and drain the fluid slowly over several hours, in hospital.
The doctor removing pleural fluid needs experience and patience.
Why is a pleural aspiration needed?
There are three main reasons:
- Firstly, to diagnose the cause of the pleural effusion.
- Secondly, to give relief from the breathlessness caused by a large pleural effusion.
- Lastly, to see whether, following the removal of most of the fluid, the lung has fully re-expanded and is sitting adjacent to the chest wall and the mediastinum (i.e. the tissues in the centre of the chest). This information is needed in the context of pleural effusion caused by a cancer. Sometimes recurrent pleural effusion caused by cancer can be eliminated by doing a 'pleurodesis'. This involves putting a chemical or talc into the pleural space (by a surgeon). However, this only works if the lung can fully re-expand against the chest wall. If the lung can re-expand, pleurodesis can be done.