About ascites (swollen tummy)

Cancer can sometimes cause swelling of the tummy (abdomen) due to a build up of fluid. The medical name for a build up of fluid in the abdomen is ascites (pronounced ay-site-eez).

A swollen tummy can be very uncomfortable but a doctor can drain the fluid to make you more comfortable.

This isn't a common problem for people with oesophageal cancer. But some people with advanced cancer might have a swollen tummy if the cancer has spread to their liver. 

Where the fluid builds up

Fluid builds up in the abdominal cavity. This is the area of the body below the ribs and lungs and above the hip bones. It contains the stomach, small and large bowel, pancreas, liver, spleen, and kidneys.

Diagram showing fluid in the abdomen

The fluid collects between the 2 layers of tissue that surround the abdominal organs. These layers are called the peritoneum. One layer lines the wall of the abdomen. The other covers the organs.

The peritoneum usually produces a small amount of fluid. This helps the organs in the abdomen to move smoothly.

Sometimes a large amount of fluid builds up between the 2 layers, which makes the abdomen swell. This can be very uncomfortable.

This fluid build up is called ascites.

What are the symptoms of ascites?

The fluid causes swelling that can make the tummy feel tight and very uncomfortable. It often develops over a few weeks but might happen over a few days.

The fluid causes pressure on other organs in the abdominal area and may lead to:

  • clothes feeling tighter or needing a bigger belt size
  • bloating
  • abdominal pain
  • back pain
  • difficulty sitting comfortably and moving around
  • loss of appetite
  • indigestion
  • constipation
  • needing to pass urine often
  • breathlessness
  • tiredness and weakness (fatigue)
  • feeling or being sick


Fluid can build up when:

  • cancer cells irritate the lining of the abdomen and make it produce too much fluid
  • lymph glands in the abdomen get blocked and can’t drain fluid properly
  • cancer has spread to the liver and raises the pressure in nearby blood vessels, which forces fluid out
  • the liver can’t make enough blood proteins so fluid leaks out of veins into the abdominal cavity


You might have tests to find the cause of the swelling.

Your doctor examines you and asks about your symptoms. They may also ask you to have:

  • an ultrasound scan
  • blood tests to check your general health and how well your liver and kidneys are working
  • a CT scan
  • a sample of the fluid taken from your abdomen to check for cancer cells or infection

Your doctor puts local anaesthetic on the skin to numb the area. Then they put a needle into your abdomen to take a sample of fluid. They use an ultrasound scan to guide them. This can be uncomfortable but isn’t usually painful.

They use a syringe to draw out some fluid to send to the laboratory. In the lab, they examine it under a microscope to look for cancer cells.


Your doctor can drain the fluid using a small tube. This is called an ascitic tap (pronounced ass-it-ic tap). Medicines can also stop the fluid building up.


A swollen abdomen can be very uncomfortable. You might find it difficult to lie flat, it can be more comfortable to sit on a chair or in a bed supported with pillows.

Let your doctor or nurse know if you have other problems, such as indigestion or feeling sick. They can prescribe medicines to help you.

Last reviewed: 
01 Nov 2019
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    J Tobias and D Hochhauser
    Wiley Blackwell, 2015

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    Oxford University Press, 2011

  • 'Malignant ascites’, chapter 7 in Management of advanced disease
    C Campbell. N Sykes, P Edmonds, and J  Wiles(eds)
    Arnold, 2004

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