Ascites in Cats (Fluid in the Abdomen)

At a glance

What is ascites? Ascites is the accumulation of fluid in the peritoneal cavity, which causes abdominal swelling.

What causes ascites in cats?

  • Heart failure
  • Kidney or liver disease
  • Ruptured bladder
  • Cancer
  • Bleeding disorders
  • Peritonitis

Diagnosis: Baseline tests, ultrasound, and sometimes biopsy.

Treatment: Address the cause and removing the fluid which may include abdominocentesis and diuretics.

What is ascites?

Also known as abdominal effusion, ascites (pronounced ass-eye-tees), is a build-up of fluid in the abdomen.

The abdominal cavity is located below the chest and is separated by the diaphragm, a thin sheet of muscle and tendon. Several organs are contained within the abdomen including the liver, spleen, stomach, pancreas, and kidneys. A membrane known as the peritoneum lines the abdominal cavity.

Types of fluids that can build up include:

  • Transudates (fluids with a low protein and cell content that pass through a membrane or tissue)
  • Exudates (fluid with a high protein content containing cells and cellular substances from the blood vessels)
  • Chyle (highly fatty lymphatic fluid draining from the intestine),
  • Blood
  • Urine


  • Right-sided congestive heart failure: Dilated cardiomyopathy, hypertrophic cardiomyopathy, a congenital anomaly. As the heart becomes less efficient at pumping, fluid begins to build up which in turn builds up pressure in the blood vessels, which forces them to leak fluid.
  • Peritonitis (inflammation of the peritoneum) – Feline infectious peritonitis, bacterial peritonitis, chylous peritonitis. The immune response mounted by the cat damages the blood vessels, causing them to leak fluid.
  • Cancer within the abdomen: Some cancers can cause a blockage to the lymphatic system, (which drains fluids that are excreted via the urine) when a blockage occurs, excess fluid can not drain properly causing fluid to build up. Tumours may also rupture, leaking fluid into the abdomen.
  • Hypoalbuminemia: Liver disease can lead to a condition known as hypoalbuminemia. Albumin is a protein that is predominantly produced and secreted by the liver, the capacity of the liver to produce albumin drops as the liver fails.
  • Kidney disease: Albumin is also lost when kidney function drops, the kidneys are no longer as effective at filtering and returning albumin to the body and instead excreting it out of the body via the urine. In both cases, decreased albumin levels lead to a drop in oncotic pressure causing fluid to leak out of the blood vessels, causing ascites.
  • Hemorrhage/bleeding disorders: Trauma can lead to an accumulation of blood within the abdomen (hemoabdomen) ingestion of rodenticide can also lead to blood clot disorders, resulting in bleeding into the abdomen.
  • Ruptured bladder: Trauma is the most common cause of a ruptured bladder which results in urine entering the abdomen (uroabdomen).


Symptoms may vary depending on the underlying cause of ascites and the amount of fluid in the abdomen. It may have a slow or sudden onset. Fluid buildup can put pressure on the stomach and chest, making it difficult for your cat to eat or breathe. Common symptoms include the following:


The veterinarian will perform a physical examination of your cat and obtain a medical history from you.

Ascites itself is relatively easy to diagnose; however, the veterinarian will need to determine the cause. Accompanying symptoms as well as diagnostics can help to narrow down the cause.

Diagnostic workup:

  • Chemistry profile: To evaluate for elevated liver enzymes, hypoalbuminemia, low BUN (blood urea nitrogen) which can all point towards liver disease.
  • Peritoneal fluid analysis: To determine the type of fluid within the abdomen (transudates, exudates, blood, urine, chyle) which can help your veterinarian narrow down the underlying cause.
  • Urinalysis: To evaluate kidney function.
  • Chest x-rays: To evaluate the heart and lungs and look for tumours.
  • Electrocardiogram (ECG): A non-invasive test that uses high-frequency sound waves to capture live images of the heart to examine the anatomy and function of the heart and valves.
  • Abdominal ultrasound: A non-invasive test that uses high-frequency sound waves to capture live images from inside the body.


Successful treatment relies on stabilising the cat as well as treating the underlying cause. The priority is to stabilise and make the cat more comfortable.

Emergency care:

  • Abdominocentesis: Removal of the fluid within the peritoneal cavity via a catheter, will help to improve his breathing by reducing pressure on the diaphragm.
  • Diuretics: Furosemide to promote the production of urine which assists in flushing excess fluids out of the body. It is important to take care when using diuretics as increased urinary excretion can lead to hypokalemia (low blood potassium).

Treat the underlying cause:

Tumours and ruptured bladder: Intravenous fluids to correct electrolyte imbalances, azotemia (high levels of nitrogen-containing compounds in the blood), and cardiac arrhythmias due to high blood potassium levels. Surgery to remove tumours or repair a ruptured bladder.

Infection: Antibiotics to treat bacterial infections.

Kidney disease: There is no cure for chronic kidney disease, but it is possible to manage the disease with a low protein prescription diet, phosphorus binders, as well as supportive care.

Liver disease: Treatment for liver disease depends on the underlying cause. Where possible, surgery for a portosystemic shunt, other treatment options include nutritional support, antibiotics, and supportive care.

Rodenticide toxicity: If ingestion was recent, gastric decontamination followed by activated charcoal to prevent further absorption. Vitamin K injections as rat poisons use up vitamin K which is necessary for the formation of clotting factors.

Right-sided heart failure: Supportive care such as oxygen therapy as well as low sodium diet, diuretics, ACE inhibitors to relax the blood vessels and lower blood pressure.


  • Julia Wilson, 'Cat World' Founder

    Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio

    View all posts