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

Feline Infectious Peritonitis (FIP) is one of the most serious viral diseases affecting cats worldwide. In India, many veterinarians see increasing cases of FIP, particularly the wet form, also known as effusive FIP. Wet FIP is typically characterised by the accumulation of abnormal fluid in the cat’s abdomen or chest cavity. This fluid buildup can cause a visibly swollen belly, difficulty in breathing, and overall weakness.

Rivalta Test: An Essential Diagnostic Tool for Detecting Wet FIP in Cats

Unfortunately, many cat owners don’t notice the early signs right away — such as a suddenly bloated abdomen, breathing difficulties or panting, weight loss, persistent fever, lethargy, or loss of appetite.

Because these symptoms are also seen in other conditions, diagnosing FIP accurately — especially the wet form — requires careful veterinary testing. One of the simplest and most effective initial screening tools is the Rivalta Test.

What Is the Rivalta Test?

The Rivalta Test is a quick and affordable diagnostic method, first developed by Italian scientist Rivalta in 1900. It helps veterinarians determine whether the fluid (effusion) collected from a cat’s body cavity is likely due to FIP or caused by other health issues.

This test is commonly performed in veterinary laboratories across India, especially as an initial screening before more advanced tests like PCR or antibody detection.

How the Rivalta Test Works

The Rivalta Test is simple and straightforward:

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

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

3. The reaction determines the result:

   • Positive result: The drop stays intact, floats, or sinks slowly — indicating a strong possibility of FIP.

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

A positive Rivalta Test strongly suggests FIP, but it’s not a final confirmation. Your vet will need to perform further diagnostic tests to verify the condition.

Accuracy of the Rivalta Test

Scientific research shows the Rivalta Test has:

• Positive predictive value: ~86%

• Negative predictive value: up to 96%

This means:

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

• A positive result must be confirmed with other tests, including:

  • Complete blood test (CBC and biochemistry)

  • FCoV antibody testing

  • Ultrasound (USG) or X-ray imaging

How the Rivalta Test Relates to Wet FIP Symptoms in Cats

One of the hallmark signs of wet FIP is a swollen or distended abdomen due to fluid accumulation. This pressure can also spread into the chest cavity, making the cat breathe heavily or pant.

While a bloated belly may result from other causes — such as bacterial infections, liver disease, heart issues, or intestinal worms — when it’s accompanied by fever, weakness, and appetite loss, FIP becomes highly suspected.

By performing the Rivalta Test, veterinarians can quickly determine whether FIP should be suspected before moving on to confirmatory tests.

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

Treatment for Wet FIP

The most effective treatment currently available for all forms of FIP — including wet FIP — is the use of GS-441524, an antiviral compound provided by BasmiFIP. This treatment has shown a success rate of over 92% when administered under proper veterinary supervision. For cats with wet FIP, GS-441524 helps the body reabsorb accumulated fluid and reduce inflammation over time.

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

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

When Should You Take Your Cat to the Vet?

If your cat shows any of the following symptoms, don’t delay — consult a veterinarian immediately:

• Swollen or bloated belly

• Breathing difficulties or panting

• Weakness and lethargy

• Persistent fever that does not subside

• Loss of appetite or thirst

Early detection makes a big difference in recovery. For expert assistance in diagnosing and treating FIP, you can reach out to the BasmiFIP India Team via Instagram, Facebook, or WhatsApp.

You can also read more educational resources and treatment guides on the BasmiFIP India website.

Frequently Asked Questions (FAQ)

1. What is wet FIP in cats?

Wet FIP is a form of Feline Infectious Peritonitis where fluid accumulates in the abdomen or chest, often making the cat’s belly look swollen or causing laboured breathing.

2. What are the common symptoms of wet FIP?

Common signs include a bloated abdomen, difficulty breathing, fever, weight loss, and weakness.

3. Does a swollen cat belly always mean FIP?

No. It can also be caused by infections, parasites, tumours, liver or heart issues. Only diagnostic tests can confirm the true cause.

4. Can FIP be cured?

FIP was once considered fatal, but with GS-441524 treatment, many cats can now make a complete recovery when diagnosed early.

5. Is FIP contagious to humans or other pets?

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

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

It has about 86% accuracy for positive cases and 96% for negatives, making it a good screening test — but not the final confirmation.

7. How can you differentiate FIP effusion from other causes?

Effusion due to FIP is typically yellowish, sticky, rich in protein (>3.5 g/dL), and Rivalta Test positive. Blood and PCR tests provide confirmation.

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

No. The Rivalta Test is only a supportive tool. Final confirmation requires PCR or antibody testing, especially for neurological or ocular FIP.

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

Most will, but false negatives can occur, particularly if the fluid sample is too small or not representative.

✅ Final Note for Indian Cat Owners:

If your cat suddenly develops a bloated belly, breathing problems, or loss of energy, don’t wait too long. Early testing using the Rivalta Test can help your vet detect FIP faster — and with GS-441524 treatment, recovery is now very possible in India too.