Ascites in Cats

Updated Sep. 12, 2023
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What is Ascites in Cats?

Ascites—also known as abdominal effusion—is the buildup of fluid in the abdomen, sometimes causing the belly to visibly swell.

The fluid that collects in the abdomen can be composed of a variety of substances, including blood, urine, or serum (the liquid component of blood). These substances can enter the abdomen due to damaged blood vessels or organs, organ enlargement, abdomen tumor growths, or abdomen inflammation.

Ascites is an uncomfortable condition because the accumulation of fluid pushes on the diaphragm, stomach, and intestines. This can cause breathing difficulties, nausea, abdominal discomfort, and low energy, among other issues. Because fluid in the abdomen is more of a symptom of an illness than its own disease, a veterinary exam and diagnostic testing are required to determine the underlying cause. Unfortunately, the cause of ascites is typically serious.

Ascites in Cats


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Symptoms of Ascites in Cats

The amount of fluid in the abdomen influences the development of symptoms. When the amount of fluid is relatively small, there may be no symptoms and X-rays are needed to diagnose ascites accurately. The buildup of large amounts of fluid in the abdomen may cause cats to develop noticeable symptoms, including the most common:

  • Abdominal discomfort—cats resist abdomen examination or vocalize while lying down

  • Abdominal swelling

  • Trouble breathing (such as increased breathing rate and increased effort) and decreased ability to engage in physical activity

  • Decreased appetite

  • Low energy and weakness

  • Coughing

  • Nausea and vomiting

  • Diarrhea

  • Changes in body temperature, either fever or hypothermia

  • Weight gain

  • Muscle wasting (loss of muscle tissue that makes a cat’s hip bones, ribs, and spine more easily felt and seen, though the amount of body fat may remain the same)

  • Increased thirst and urination

  • Heart murmur and weak pulse, if heart failure is the cause

Causes of Ascites in Cats

Cats can develop ascites for many reasons, including:

  • Right-sided heart failure—when the right side of the heart is unable to pump efficiently, leading to increased pressure on blood vessels and forcing fluid from the blood vessels into the abdomen.

  • Liver disease—liver dysfunction can cause a decrease in the production of albumin, a protein found in the bloodstream.

  • Intestinal parasites—cause protein loss from the blood through the GI tract, which is another cause of fluid moving into the abdominal cavity.

  • Nephrotic syndrome—an inflammation of the kidneys, causing loss of protein from the blood so that fluid in the kidneys’ inflamed blood vessels moves into the abdomen. Nephrotic syndrome itself can be caused by kidney infection, kidney cancer, or immune-mediated diseases that cause the body’s immune cells to attack and damage healthy kidney cells.

  • Internal trauma—due to falls from high places or being hit by a car. Blood vessel rupture can lead to blood leaking into the abdomen, and bladder rupture can lead to urine leaking into the abdomen.

  • Bladder rupture—due to blockage from stones or blood clots.

  • Enlarged liver or spleen—may put pressure on lymph nodes and lymph vessels in the abdomen, preventing fluid from draining from the abdomen.

  • Peritonitis—inflammation of the lining of the abdomen (peritoneum) due to infection leads to ascites as the cells lining the abdomen become inflamed and produce too much fluid.

  • Cancer—such as carcinomatosis (carcinoma throughout the abdomen) can cause fluid accumulation in the abdomen by irritating the peritoneum in a similar manner as peritonitis, with cells producing excess fluid.

How Veterinarians Diagnose Ascites in Cats

In addition to the clinical signs described above, veterinarians use several tests to diagnose ascites. Imaging methods such as X-ray and ultrasound are the most common diagnostic tests used to look for fluid in the abdomen, and imaging also allows evaluation of organs such as the liver, spleen, kidneys, bladder, intestines, and heart to help identify the cause.

If imaging is not conclusive, other diagnostic tests such as a blood chemistry panel, complete blood count, urinalysis, and stool examination are often required to determine the cause of ascites. The veterinarian may also collect a sample of the abdominal fluid to determine its composition, looking for components like blood, bacteria, protein, or cancerous cells.

Treatment of Ascites in Cats

Treatment of ascites in cats depends upon the cause.

In some cases, the underlying cause may not be correctable, so treatment may involve surgery to place a catheter in the abdomen to allow fluid to drain. Fluid that builds up slowly may only require periodic draining while your cat is sedated. Surgical correction to prevent further fluid buildup may be necessary in cases of tumors, hemorrhage from trauma, bladder rupture from injury, or urinary blockage.

In other instances such as heart failure or liver disease, medications specific to the condition may be prescribed to reduce fluid accumulation in the abdomen. Carcinomatosis or other cancers that have spread throughout the body may need to be treated with chemotherapy rather than surgery.

Bacterial causes of ascites such as peritonitis and sepsis need to be treated with antibiotics. Although cats with abdominal fluid caused by conditions such as heart failure, liver disease, or sepsis may not be stable enough to safely undergo surgical procedures, medical management is typically the best form of treatment.  

Recovery and Management of Ascites in Cats

The timeline for recovery, overall prognosis, and chances of ascites recurring also depends on the underlying cause.

Medications and low-sodium diets can help slow the rate of accumulation of fluid in the abdomen, but these therapies may not prevent ascites from recurring. Since ascites can be complicated to manage in cases of chronic or severe disease, it is crucial to take cats suspected of having fluid in the abdomen to a veterinarian or animal hospital as soon as possible.

The cat can be given the best chance of comfort and healing as the ascites is being addressed by following the veterinarian’s instructions for treatment and management, including rechecks to assess progress.

Featured Image:

Hannah Hart, DVM


Hannah Hart, DVM


Dr. Hart graduated from veterinary school in 2017 and began her career with USDA Food Safety and Inspection Service as a public health...

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