Ascites is a buildup of fluid in your abdominal cavity. About one-third of people with ovarian cancer will have ascites at the time of their initial cancer diagnosis.

Most generally healthy people have very little free fluid inside their abdomen — usually no more than 20 milliliters. But when you have ascites, large amounts of fluid collect in the free space around your organs.

Ascites has many potential causes. In the United States, cancer accounts for about 10% of ascites cases. Ovarian cancer is the most common cause of cancer-related ascites.

The presence of ascites can affect disease outlook. Ascites can both indicate and contribute to ovarian cancer metastasis (spread) and to the development of chemotherapy resistance.

This article examines the relationship between ascites and ovarian cancer.

Ascites is quite common in ovarian cancer overall. About one-third of people with ovarian cancer have ascites at the time of their cancer diagnosis.

But ascites can also indicate that ovarian cancer has spread. It’s present in more than 90% of people with stage 3 or 4 ovarian cancer and in nearly all cases of ovarian cancer recurrence.

Ascites is associated with certain tumor types, including the most common aggressive subtype of ovarian cancer, high grade serous ovarian cancer.

A variety of processes can lead to ascites in ovarian cancer. For example:

  • Cancer cells can release substances that make your blood vessels and peritoneum leaky, allowing excess fluid to build up in your abdomen.
  • Cancer can block normal lymphatic drainage of your abdominal cavity, causing a fluid backup and leading to ascites.
  • As cancer spreads, it can directly damage your peritoneum or cause increased pressure in your major veins. Either of these effects can cause fluid leakage into your abdomen.
  • The substances in ascites fluid itself, including cancer cells, nutrients, and signaling molecules, can encourage cancer spread, leading to further worsening of ascites.

Causes of ascites

Cancer-related ascites accounts for about 10% of ascites cases in the United States. Ascites is commonly associated with the following cancers:

  • ovarian
  • endometrial
  • pancreatic
  • gastric
  • colorectal
  • peritoneal
  • liver
  • lung
  • breast

Common non-cancer-related causes of ascites include:

  • liver cirrhosis (which causes 80% of ascites cases in the United States)
  • pancreatitis
  • nephritis or nephrotic syndrome
  • heart failure
  • tuberculosis

Common symptoms of ascites include:

  • progressive abdominal swelling and tightness
  • abdominal discomfort
  • weight changes
  • nausea
  • decreased appetite or a tendency to feel unusually full while eating
  • shortness of breath
  • changes in bowel or bladder habits
  • back pain
  • fatigue

If ascites fluid becomes infected, you may also experience fever and abdominal pain.

Your doctor can often diagnose ascites based on a physical exam or imaging, such as an ultrasound or CT scan.

Once your doctor diagnoses ascites, they may recommend paracentesis. During this procedure, a healthcare professional uses a needle to remove some of the fluid and examine its components.

The two types of paracentesis

There are two types of paracentesis:

  • Diagnostic paracentesis: A healthcare professional removes a small amount of ascites fluid (often in milliliters) for testing purposes, such as to check for cancerous cells.
  • Therapeutic paracentesis: A healthcare professional removes ascites fluid (often in liters) to relieve related symptoms.

In some people who have malignant ascites due to early stage ovarian cancer, treating the underlying cancer may help resolve ascites.

For others, diuretics may be used to reduce ascites fluid.

If you’re experiencing significant symptoms (such as pain or shortness of breath) due to your ascites, your doctor may recommend paracentesis to drain a large amount of the fluid at once.

They may need to repeat paracentesis later, since ascites can recur.

Because ovarian cancer causes few overt early symptoms, it’s often diagnosed at more advanced stages. Ascites may indicate that ovarian cancer has spread.

Ascites fluid is more than just a byproduct. It provides a nutrient-rich medium that allows tumor cells to spread to and invade other abdominal organs. Research has shown that certain cellular compounds in ascites fluid can also contribute to resistance to common chemotherapy drugs.

For these reasons, the presence of ascites, especially in larger volumes, has been associated with a less favorable outlook for ovarian cancer. Researchers are actively exploring whether drugs that help prevent ascites may improve the outlook for people with ovarian cancer.

It’s important to remember that many other factors also contribute to your outlook with ovarian cancer, including tumor cell features, age, and initial surgical outcomes.

Your doctor can best help you understand your individual risk factors and outlook.

Ascites is a buildup of free fluid in your peritoneal cavity. Ovarian cancer is the most common cause of malignancy-related ascites in the United States.

Ovarian cancer often causes vague and limited early symptoms, and ascites frequently occurs at advanced stages of the cancer. Ascites may indicate that ovarian cancer has spread or recurred.

Ascites fluid itself can also be a risk factor for further cancer spread and the development of chemotherapy resistance.

In some cases, treating the underlying cancer can help resolve ascites. If this does not help, healthcare professionals can drain the fluid to ease related symptoms such as abdominal distension and shortness of breath.

If you’re experiencing symptoms that could indicate ascites, such as persistent abdominal pain, bloating, or shortness of breath, talk with a doctor right away.