Wet FIP
Effusive Feline Infectious Peritonitis
Understanding the Effusive Form of FIP in Cats
Wet FIP, also known as effusive Feline Infectious Peritonitis, is the most common and often rapidly progressive clinical form of FIP. It is characterized by the accumulation of protein-rich fluid in body cavities, most frequently the abdomen (ascites) or the chest (pleural effusion).
Wet FIP occurs when a mutated feline coronavirus triggers an abnormal immune response, leading to inflammation of blood vessels (vasculitis). Increased vascular permeability allows fluid and proteins to leak into surrounding tissues and cavities, producing visible swelling and respiratory compromise in affected cats.
Key Clinical Features
Cats with wet FIP commonly exhibit:
Abdominal enlargement caused by fluid buildup
Difficulty breathing when fluid accumulates in the chest
Persistent or recurrent fever that responds poorly to antibiotics
Lethargy and reduced activity
Loss of appetite and weight loss
Dehydration and poor coat condition
Clinical progression may be rapid, especially in younger cats or cats with weakened immune systems.
Diagnostic Considerations
Wet FIP is often easier to suspect clinically than other forms due to visible fluid accumulation. However, no single test alone confirms FIP, and diagnosis relies on a combination of findings.
Common diagnostic approaches include:
Ultrasound or radiography to identify abdominal or thoracic effusion
Fluid analysis, evaluating protein concentration, viscosity, and cellular content
Blood tests, including globulin levels and inflammatory markers
PCR testing on effusion samples in selected cases
Clinical pattern recognition and response to supportive care
Veterinary interpretation is essential to differentiate wet FIP from other causes of effusion, such as heart disease, liver disease, or bacterial infections.
Clinical Management Overview
Management of wet FIP focuses on:
Stabilizing respiratory function if pleural effusion is present
Monitoring hydration and nutrition
Managing inflammation and secondary complications
Supporting overall comfort and quality of life
Antiviral research has significantly advanced in recent years, but all treatment decisions should be guided by a licensed veterinarian based on individual clinical evaluation.
Prognosis and Monitoring
Historically, wet FIP carried a guarded prognosis due to rapid progression. Early recognition, careful monitoring, and timely veterinary intervention may improve clinical outcomes and comfort.
Ongoing monitoring may include:
Repeat imaging
Blood parameter trends
Weight and appetite tracking
Behavioral and activity assessments
Authoritative References
The information on this page is based on internationally recognized veterinary sources:
World Small Animal Veterinary Association (WSAVA) – Global FIP Guidelines
Cornell Feline Health Center – Feline Infectious Peritonitis Overview
Merck Veterinary Manual – Feline Infectious Peritonitis
Journal of Feline Medicine and Surgery – Peer-reviewed clinical research
Medical Disclaimer
Important: All content on this page is provided for educational purposes only and does not constitute veterinary diagnosis, treatment, or medical advice. Always consult a licensed veterinarian for any health-related decisions concerning your pet.
