What is ascites?

The medical name for a build up of fluid in the abdomen is ascites (pronounced ay-site-eez). It can also be called malignant ascites.

The tummy (abdomen) contains many organs, including the stomach, bowels, pancreas, liver, spleen and kidneys. There is a sheet of tissue (peritoneum) around these organs. It is made up of 2 layers. One layer lines the wall of the abdomen. The other covers the organs.

The layers produce a small amount of fluid so that the organs in the abdomen can move smoothly. Sometimes fluid builds up between the 2 layers, which makes the abdomen swell. This can be very uncomfortable.

This fluid build up is called ascites.

Diagram showing fluid in the abdomen

The causes of ascites

Cancers that can cause ascites include:

  • ovarian cancer
  • breast cancer
  • bowel cancer
  • stomach cancer
  • pancreatic cancer
  • mesothelioma in the peritoneum
  • lung cancer
  • liver cancer
  • womb cancer

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

Other conditions that can cause fluid in the abdomen include:

  • liver disease
  • heart disease

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


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.

  • Cancer Priniciples & Practice of Oncology (11th edition)
    VT DeVita and others
    Lippincott, Williams and Wilkins 2018

  • Cancer and its Management (7th edition)
    J Tobias and D Hochhauser 
    Wiley-Blackwell 2014

  • Diagnosis and treatment of ascites
    EA Tsochatzis and AL Gerbes
    Journal of Hepatology, 2017, Volume 67, Issue 1, Pages 184–185

Last reviewed: 
26 Apr 2021
Next review due: 
26 Apr 2024

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