What Causes Fluid to Collect in the Abdomen?

The collection of more fluid than normal in the abdominal cavity is called ascites. It is often described in everyday speech as “water gathering in the abdomen”.

A small amount of fluid may not be noticed by the patient. As the amount increases, there may be an increase in abdominal girth, tightness, weight gain, early satiety and sometimes breathlessness.

Newly developed fluid in the abdomen is not a disease in itself. It is an important finding whose underlying cause needs to be established.

Fluid in the abdomen has several different causes, and on its own it does not mean cancer.

Is every swollen abdomen a collection of fluid?

No.

An increase in abdominal girth, or bloating, can arise from different causes such as:

• Wind
• Constipation
• Weight gain
• Masses within the abdomen
• Enlargement of organs
• The collection of fluid in the abdominal cavity

For this reason one cannot say “there is fluid in my abdomen” by looking at its appearance alone.

Ultrasound is a very useful method for showing whether or not there is fluid within the abdomen.

What is the commonest cause of fluid collecting in the abdomen?

One of the most important causes of ascites is advanced chronic liver disease and cirrhosis.

In cirrhosis, the resistance to blood flow within the liver increases and portal hypertension can develop. Hormonal changes that lead the kidneys to retain salt and water are added to the picture.

As a result, fluid can collect in the abdominal cavity.

Not all ascites is due to cirrhosis, however.

What diseases other than liver disease can cause ascites?

The collection of fluid in the abdomen has various causes.

These may include:

• Certain cancers
• Heart failure
• Certain kidney diseases
• Diseases of the pancreas
• Certain infections such as tuberculosis
• Other, rarer conditions

For this reason it is important to investigate the cause, particularly where ascites is found for the first time.

What symptoms appear when fluid collects in the abdomen?

Depending on the amount of fluid and the underlying disease, there may be:

• A steadily increasing abdominal girth
• Tightness and a feeling of heaviness in the abdomen
• Rapid weight gain
• Early satiety
• Loss of appetite
• Breathlessness
• Swelling of the feet and legs

In people with liver disease, jaundice, loss of muscle or other signs of liver disease may also accompany it.

Why does ascites cause breathlessness?

When a large amount of fluid collects in the abdomen, it can press upwards on the diaphragm.

This makes it harder for the lungs to expand freely and can cause breathlessness, particularly where the ascites is large in volume.

How is ascites established?

The doctor first takes the patient’s history and examines the abdomen.

Ultrasound is one of the basic imaging methods for showing fluid in the abdomen, and can also show small amounts of fluid that could not be detected on examination.

Where necessary, other imaging methods such as computed tomography can be used.

Why is fluid taken from the abdomen?

Taking a sample of the fluid within the abdomen with a needle is called paracentesis.

Examining the fluid can help to establish the cause of the ascites, particularly where it is newly developed or in certain situations requiring admission to hospital.

The fluid obtained can be examined for:

• A cell count
• Albumin and protein
• Tests relating to infection
• Cytological and other tests where required

The serum-ascites albumin gradient (SAAG), calculated using the albumin values in the blood and in the ascitic fluid, helps in assessing whether or not the collection of fluid is related to portal hypertension.

Is paracentesis only carried out for diagnosis?

No.

Where a great deal of fluid has collected in the abdomen and the patient has marked tightness, pain, early satiety or breathlessness, part or a large amount of the fluid can be drained for treatment.

This is called therapeutic paracentesis.

After large-volume paracentesis, some patients may need albumin given intravenously.

How is fluid in the abdomen treated?

Treatment is determined first of all by the cause of the ascites.

In ascites due to cirrhosis, the important parts of treatment may include:

• Reducing salt intake
• Diuretic medicines in suitable patients
• Monitoring body weight and kidney function
• Paracentesis where required
• Treatment of the underlying liver disease

In some patients with advanced disease resistant to treatment, procedures such as TIPS, or assessment for liver transplantation, may come onto the agenda.

The same treatment is not applied in every patient.

Does drinking a lot of water increase ascites?

The basic approach in the treatment of ascites is generally restriction of salt.

Not every patient with ascites needs to restrict fluid severely as a matter of routine. Fluid restriction may be advised by a doctor particularly in selected patients whose blood sodium level has fallen markedly.

For this reason it is not right for patients to restrict their water intake excessively on their own.

Can ascites become infected?

Yes.

In people with ascites due to cirrhosis in particular, infection can develop in the ascitic fluid without any other obvious focus of infection. This is called spontaneous bacterial peritonitis (SBP).

There may be fever, abdominal pain or tenderness. In some patients, however, the symptoms can be more subtle.

In a person with cirrhosis and ascites, assessment is required without delay where there is:

• Fever
• Newly started abdominal pain
• A change in consciousness
• Marked weakness
• A deterioration in kidney function

When should a doctor be consulted?

Assessment should be carried out particularly where there is:

• An unexplained and steadily increasing abdominal girth
• Marked weight gain over a short period
• Swelling of the legs
• Jaundice
• Early satiety and loss of appetite
• Breathlessness

Fluid found within the abdomen for the first time should have its cause investigated.

When is urgent assessment required?

Urgent medical assessment may be required if the collection of fluid in the abdomen is accompanied by:

• Fever or shivering
• Newly started or severe abdominal pain
• Confusion or excessive drowsiness
• Marked breathlessness
• Vomiting blood
• Black stools
• A marked reduction in the amount of urine

Remember

Not every swollen abdomen is ascites, and not every ascites is due to cirrhosis.

Where fluid has newly collected in the abdomen, trying to reduce the fluid alone is not enough.

What matters is to establish why the fluid has collected and to treat the underlying disease.