Understanding the Rivalta Test: A Key Diagnostic Tool for Detecting Wet FIP in Cats

Feline Infectious Peritonitis (FIP) has long been one of the most feared viral diseases among cat owners. Once considered fatal, FIP — especially its wet (effusive) form — is now treatable thanks to advancements in antiviral therapy such as GS-441524, made available through CureFIP.

In the U.S., many veterinarians are increasingly recognizing FIP cases earlier, often using a simple yet valuable diagnostic tool known as the Rivalta Test.

If your cat has developed a swollen belly, is breathing faster than usual, or seems weak and lethargic, this test may help your vet determine whether it’s FIP or another condition.

What Is the Rivalta Test?

The Rivalta Test is a simple diagnostic procedure developed in 1900 by an Italian scientist named Rivalta. It’s designed to help veterinarians distinguish whether the fluid (effusion) found in a cat’s abdomen or chest is likely due to FIP or another underlying medical problem, such as infection or organ failure.

Understanding the Rivalta Test: A Key Diagnostic Tool for Detecting Wet FIP in Cats

In the U.S., this test is typically performed in a veterinary lab as part of an initial screening before moving to more advanced tests such as PCR analysis or FCoV antibody testing.

How the Rivalta Test Works

The process is straightforward and can be done quickly by most veterinary laboratories:

1. A test tube is prepared with distilled water and a few drops of acetic acid (vinegar).

2. A small amount of the cat’s effusion fluid (fluid from the abdomen or chest) is dropped into the tube.

3. The reaction determines the result:

   • Positive result: The drop remains intact, floats, or sinks slowly — suggesting FIP.

   • Negative result: The drop dissolves immediately and the solution stays clear — suggesting another cause.

A positive Rivalta Test result doesn’t confirm FIP by itself, but it strongly supports the diagnosis when paired with clinical signs and lab findings.

Accuracy of the Rivalta Test

Multiple studies have confirmed the reliability of the Rivalta Test:

• Positive predictive value: around 86%

• Negative predictive value: up to 96%

In other words, a negative result often rules out FIP, while a positive result should be confirmed with further testing such as:

• Blood panel (CBC and biochemistry)

• Ultrasound or X-ray imaging

• PCR testing for Feline Coronavirus (FCoV)

How the Rivalta Test Relates to Wet FIP Symptoms

The most visible symptom of wet FIP is a bloated or swollen abdomen due to fluid buildup inside the body. In some cats, this fluid also accumulates around the lungs, leading to breathing difficulties or panting. While a swollen belly can also result from infection, liver disease, heart failure, or parasites, if your cat shows persistent fever, loss of appetite, and lethargy along with these signs, FIP becomes a strong possibility.

Using the Rivalta Test, veterinarians can perform quick early screening to decide if FIP is likely before proceeding with more specific diagnostics.

👉 Read more: Understanding FIP and How CureFIP Treatment Works

Treatment for Wet FIP in the U.S.

The good news is that wet FIP is now treatable. The antiviral GS-441524, used in the CureFIP protocol, has shown a recovery rate of over 90% when administered correctly under veterinary guidance.

For cats with wet FIP, GS-441524 helps:

• Stop the virus from replicating

• Allow the body to reabsorb excess fluid

• Restore appetite and energy

If fluid builds up in the chest (pleural effusion) and causes breathing difficulty, veterinarians may perform a thoracocentesis procedure to safely remove the fluid and help the cat breathe normally.

For abdominal fluid (ascites), only partial drainage (20–30% at a time) is typically recommended to avoid sudden blood pressure drops or shock.

When to See Your Veterinarian

Contact your vet immediately if your cat shows:

• A swollen or distended belly

• Breathing difficulties or panting

• Persistent fever

• Weight loss or poor appetite

• Weakness or lethargy

Early diagnosis and treatment offer the best chance of recovery. The earlier antiviral therapy begins, the better the outcome. For professional advice or treatment options, visit your local veterinarian or reach out to the CureFIP Support Team for guidance and assistance.

👉 Learn more: https://www.curefipusa.com 

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, making the belly appear bloated and breathing more difficult.

2. What are the symptoms of Wet FIP?

Common symptoms include abdominal swelling, labored breathing, fever, lethargy, and loss of appetite.

3. Does a bloated belly always mean FIP?

No. It can also be caused by infections, organ disease, or parasites. Only diagnostic testing like the Rivalta Test can confirm the cause.

4. Can FIP be cured?

Yes. With GS-441524 antiviral therapy under the CureFIP protocol, many cats recover completely and go on to live healthy lives.

5. Is FIP contagious to humans or other pets?

No, FIP is not contagious to humans. However, the underlying Feline Coronavirus (FCoV) can spread between cats.

6. How reliable is the Rivalta Test?

It’s about 86% accurate for positive results and 96% for negatives. It’s a good screening tool but not definitive.

7. Can the Rivalta Test replace PCR testing?

No. The Rivalta Test is a quick screening method; PCR or antibody tests are used for confirmation.

Final Note for U.S. Cat Owners

If your cat suddenly develops a swollen belly, trouble breathing, or unexplained fever, don’t wait. Ask your vet about the Rivalta Test — it’s simple, inexpensive, and could be the key to an early diagnosis.

Thanks to CureFIP and GS-441524 therapy, FIP is no longer a death sentence. Thousands of cats across the U.S. have regained their health, energy, and happiness after treatment.

👉 Learn more about treatment, recovery stories, and support at www.curefipusa.com