Draining fluid from your chest or tummy

Cancer cells can inflame the lung lining (pleura) or abdominal lining (peritoneum). This can cause fluid to build up. The fluid might contain cancer cells.

Fluid around the lungs is called a pleural effusion. It can make it difficult to breathe. Draining fluid from your chest is called thoracocentesis or pleural aspiration.

Fluid in the tummy (abdomen) is called peritoneal ascites. It can make the abdomen feel swollen, tight and uncomfortable. Draining fluid from your abdomen is called an abdominal paracentesis.

Why you might have it

The doctors might drain fluid from around your lungs or abdomen to:

  • see if the fluid contains cancer cells
  • help control symptoms 

Preparing for the drainage

The doctor can often drain the fluid on the ward or as a day patient. You might need to stay in hospital overnight. You have a local anaesthetic which means you are awake.

To drain fluid around your lungs, you sit on a chair or on the edge of the bed. You lean forward over a table with a pillow on it.

To drain fluid in your abdomen, you can lie down on a bed or a reclining chair.

Draining fluid during surgery

Sometimes, the doctor might drain fluid during a small operation called a thoracoscopy or a laparoscopy. You have these operations in an endoscopy suite or operating theatre.  You can read about preparing for a thoracoscopy and a laparoscopy in the general test section.

What happens?

The doctor cleans your skin with antiseptic. They numb the area with an injection of local anaesthetic.

To drain the fluid off, your doctor uses a needle (cannular) to put a small tube into the chest or abdomen. They attach this to a tube with a bag at the end of it. The fluid drains through the tube into the bag. 


Diagram showing fluid drainage treatment
Diagram showing fluid (ascites) being drained from the abdomen

After the test

The doctor might make a couple of stitches in the skin to hold the catheter in place. You have a dressing over the tube which also helps to keep it in position.

You might only need to have the tube in for a few hours. But there is a lot of fluid, you might have the drain in for a few days. Some people might have a permanent drain that can stay in for a few months.

The doctor sends a sample of the fluid to a laboratory for testing. This is to see if it contains cancer cells.

Possible problems

Low blood pressure

Your blood pressure may drop and make you feel ill if the fluid drains too quickly. Your nurses will check your blood pressure and pulse regularly.

Pain and discomfort

Your nurse can give you painkillers if you need them. They can also help you change your position to make you comfortable.


The tube can block. This stops the fluid from draining. Your doctor or nurse might ask you to change position or sit upright to see if this helps the tube to drain again. If this doesn’t work, the doctor might need to remove the tube and put in a new one.

A collapsed lung (pneumothorax)

After the fluid drains from around your lung, air can collect in the space. This can make the lung collapse. This is called a pneumothorax. Contact a doctor if you become short of breath or have chest pain. You might not need any treatment and it goes on its own. Sometimes, your doctor might need to put another tube into the lung to remove the air.


There is a small risk of infection. Your nurse will check the site where the tube is for any signs of infection. They will also monitor your temperature. You can have antibiotics if you develop an infection.


There is a small risk of bleeding when the doctors put in the tube. This usually stops without any treatment.

Getting your results

You should get your results within 1 or 2 weeks. The doctor may be able to tell you if they have seen any cancer cells in the fluid sample that was sent to the laboratory.

Waiting for results can make you anxious. Ask your doctor or nurse how long it will take to get them.

Contact the doctor who arranged the test if you haven’t heard anything after a couple of weeks.

You might have contact details for a specialist nurse and you can contact them for information if you need to. It can help to talk to a close friend or relative about how you feel.

For information and support, you can also call the Cancer Research UK nurses on freephone 0808 800 4040. The lines are open from 9am to 5pm, Monday to Friday.

  • Malignant pleural mesothelioma: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up
    S. Popat and others
    Annals of Oncology, 2022 Volume 33, Issue 2, Pages 129 – 142

  • The Royal Marsden Manual of Clinical Nursing Procedures (10th edition)
    S Lister, J Hofland and H Grafton 
    Wiley Blackwell, 2020

Last reviewed: 
19 May 2023
Next review due: 
19 May 2026

Related links