Does Abdominal Fluid in Cats Always Mean FIP?

1 Common Causes of Ascites in Cats

Abdominal fluid in cats, also called ascites, is a buildup of excess liquid in the belly. Many things can cause it, and FIP is only one possibility. Here are the usual culprits and how vets tell FIP apart.

1. Liver disease. Cirrhosis, hepatitis, and liver tumors are common sources of ascites; they let excess fluid leak out and collect in the abdomen.

2. Heart problems. Dilated or hypertrophic cardiomyopathy, congenital defects, and pericardial effusion can all cause ascites by weakening the heart’s pumping and letting fluid seep from vessels.

3. Kidney disease. Kidney failure and nephritis disrupt the body’s fluid balance and can lead to abdominal fluid.

4. Malnutrition. Long-term poor nutrition can drain the body’s protein and lower blood colloid pressure, triggering ascites.

5. Peritonitis. Inflammation of the abdominal lining produces fluid; bacteria, viruses, or trauma can cause it, and FIP is one form of this.

2 Signs of Feline Infectious Peritonitis

FIP is a systemic disease caused by a coronavirus, spread through infected feces. Affected cats may show: reduced appetite; lethargy and unwillingness to move; repeated fever of 39.5–40.6 °C; rapid or difficult breathing; a gradually swelling belly with a fluid wave you can feel; and weight loss from poor eating.

FIP comes in dry and wet forms. Dry FIP often shows eye signs—nystagmus, blurred vision, lens clouding—while wet FIP shows belly signs: rising fluid, a bloated abdomen, and thinning body. A few dry-form cats also develop anemia, jaundice, or nerve signs such as limb twitching or hind-leg paralysis, and nodules can appear in organs including the liver, kidneys, and lymph nodes.

3 How Vets Confirm the Diagnosis

Beyond the symptoms, professional testing is needed: 1. Laboratory work—blood count, serum biochemistry, and urinalysis to assess overall health. In FIP, low albumin, high globulin, and high cholesterol are suggestive. 2. Imaging—X-ray and abdominal ultrasound to check for fluid and organ inflammation. 3. Viral testing—a stool or abdominal-fluid sample tested for feline coronavirus (FCoV); a positive result supports a FIP diagnosis.

Whatever the cause, abdominal fluid is dangerous. If your cat develops ascites or other worrying signs, go to a veterinary clinic promptly, find the cause, and start treatment without delay.