Understanding the Rivalta Test: An Important Tool for Detecting Wet FIP in Cats

Feline Infectious Peritonitis (FIP) is one of the most serious viral diseases that can affect cats. Among its forms, wet FIP (also called effusive FIP) is the most common type. It’s typically characterised by the buildup of abnormal fluid inside the cat’s abdomen or chest cavity.

Rivalta Test: An Important Tool for Detecting Wet FIP in Cats

Many cat owners in the Philippines often don’t notice the early signs right away — such as a suddenly swollen belly, breathing difficulties or panting, weight loss, persistent fever, stress, or loss of appetite and thirst.

Because these symptoms are similar to other illnesses, diagnosing FIP — especially the wet form — requires careful veterinary examination. One of the most widely used initial screening tools for this condition is the Rivalta Test.

What Is the Rivalta Test?

The Rivalta Test is a simple diagnostic method first developed by Italian scientist Rivalta in 1900. It helps veterinarians determine whether the fluid found inside a cat’s body cavity (called effusion) is likely caused by FIP or by another health issue.

The test is affordable, quick, and widely available in many vet clinics, making it a helpful screening tool before performing more advanced diagnostics such as PCR or antibody tests.

How the Rivalta Test Works

The procedure for the Rivalta Test is straightforward and can be done in most veterinary laboratories:

1. A test tube is filled with distilled water and a few drops of acetic acid.

2. A small sample of the cat’s body fluid (effusion) is dropped into the solution.

3. The reaction of the drop determines the result:

   • Positive Result: The drop stays intact, floats, or sinks slowly — suggesting possible FIP.

   • Negative Result: The drop dissolves quickly and the liquid remains clear — suggesting another cause.

A positive Rivalta Test strongly suggests wet FIP, although it’s not a definitive diagnosis. Further testing is always recommended.

Accuracy of the Rivalta Test

Studies show that the Rivalta Test has a positive predictive value of about 86% and a negative predictive value of up to 96%.

This means:

• A negative result can reliably rule out FIP in most cases.

• A positive result should be confirmed through additional tests such as:

  • Complete blood test (CBC, biochemistry)

  • Feline coronavirus (FCoV) antibody test

  • Ultrasound (USG) or X-ray examination

How the Rivalta Test Relates to Wet FIP Symptoms in Cats

One of the most noticeable signs of wet FIP is a swollen or bloated abdomen due to fluid accumulation. This fluid buildup can also spread to the chest cavity, causing breathing difficulties or panting.

While a bloated belly can result from other conditions — such as bacterial infections, liver disease, heart problems, or intestinal worms — if it’s accompanied by fever, lethargy, or poor appetite, FIP becomes a strong possibility.

By using the Rivalta Test, veterinarians can perform an early screening to identify whether FIP might be the cause before moving on to more specific tests.

👉 Read more: Understanding FIP in Cats and How to Manage It

Treatment for Wet FIP

The most effective treatment for all forms of FIP — including the wet form — involves using GS-441524, an antiviral medication provided by BasmiFIP.

This medication has shown a success rate of over 92% when administered with the correct dosage and treatment protocol. For cats with wet FIP, GS-441524 helps the body gradually absorb the excess fluid and reduce inflammation.

In some cases, if fluid builds up in the chest (pleural effusion) and causes breathing difficulty, the veterinarian will perform a thoracocentesis procedure to remove 100% of the pleural fluid to help the cat breathe normally again.

However, for abdominal fluid (ascites), only 20–30% of the fluid should be drained at one time to avoid sudden drops in blood pressure or shock.

When Should You Bring Your Cat to the Vet?

If you notice any of the following signs, don’t delay — bring your cat to a veterinarian right away:

• Swollen or enlarged belly

• Breathing difficulties or panting

• Weakness and lethargy

• Persistent fever that doesn’t go down

• Loss of appetite or thirst

Early diagnosis can greatly improve your cat’s chances of recovery.

For expert advice or help with diagnosing and treating FIP, you can reach out to the BasmiFIP Philippines Team through Facebook, Instagram, or Viber.

You can also check out more educational articles and consultations on the BasmiFIP PH website.

Frequently Asked Questions (FAQ)

1. What is wet FIP in cats?

Wet FIP is a form of Feline Infectious Peritonitis that causes fluid buildup in the cat’s abdomen or chest, often making the belly look swollen and the cat struggle to breathe.

2. What are the common symptoms of wet FIP?

The most common signs include a bloated abdomen, breathing difficulties, fever, weight loss, and weakness.

3. Does a swollen belly always mean FIP?

No. A bloated belly can also be caused by infections, parasites, tumours, liver or heart problems. Only diagnostic tests can confirm the true cause.

4. Can FIP be cured?

Previously, FIP was considered fatal. But with GS-441524, many cats now fully recover when treated early and consistently.

5. Is FIP contagious to humans or other pets?

No, FIP itself is not contagious to humans. However, the virus that causes it (Feline Coronavirus, FCoV) can spread among cats.

6. How accurate is the Rivalta Test for diagnosing FIP?

It has about 86% accuracy for positive results and 96% for negatives. It’s reliable for screening but not a final confirmation.

7. How can you tell if effusion is due to FIP or something else?

FIP effusion is usually yellowish, thick, protein-rich (>3.5 g/dL), and Rivalta Test positive. Blood tests and PCR can help confirm.

8. Can the Rivalta Test replace PCR or FCoV antibody testing?

No. Rivalta is only a supportive test. Confirmation still requires PCR or serology, especially for neurological or eye-related FIP cases.

9. Will all wet FIP cases show a positive Rivalta Test?

Most will, but there may be false negatives if the fluid sample is small or not representative.

✅ Final Note for Filipino Cat Owners:

If your cat shows sudden changes — like a swollen belly, breathing problems, or loss of energy — don’t wait too long. Early screening using the Rivalta Test can save lives. With GS-441524 treatment, many cats in the Philippines have already made full recoveries.