🫀 Pericardial Effusion in Dogs and Cats: A 2025 Vet Guide to Heart Sac Fluid Buildup 🐶🐱

By Dr Duncan Houston, BVSc

Pericardial effusion — fluid buildup around the heart — is an uncommon but serious condition in pets. Thanks to modern tools like ultrasound, it’s being diagnosed more frequently. In this guide, I’ll explain what it means for your dog or cat, what symptoms to watch for, and how we treat it in 2025. 🐾🩺

💡 What Is Pericardial Effusion?

The pericardium is a thin, two-layered sac that surrounds the heart. Normally, it contains only a small amount of lubricating fluid. But in pericardial effusion, fluid builds up excessively, placing pressure on the heart. 🧯

This pressure acts like a tight jacket around the heart, stopping it from filling with blood and pumping properly. When this happens, the body goes into shock due to low oxygen and blood flow. If untreated, this can be fatal. 🚨

🕰️ Acute vs Chronic

• ⚡ Acute cases: Fluid builds quickly, leading to sudden collapse
• 🐢 Chronic cases: Fluid accumulates slowly, causing signs like abdominal swelling or reduced activity

🩸 What Causes the Fluid Buildup?

There are three main types of fluid that may collect in the pericardial sac:

• 🩸 Blood – most common in dogs
• 🦠 Pus – due to infection or foreign bodies
• 💧 Clear or slightly bloody fluid – due to inflammation, autoimmune issues, or idiopathic causes

🐶 Common Causes in Dogs

• 🧬 Hemangiosarcoma: A cancerous tumor on the heart, causing bleeding
• 🧪 Rat poison: Interferes with blood clotting, leading to bleeding
• 🫀 Heart rupture: From advanced heart disease (rare)

🐱 Causes in Cats

• 🐈 Feline Infectious Peritonitis (FIP): A viral disease that may lead to effusion
• ❓ Idiopathic: Unknown cause, sometimes self-limiting

🔍 Clinical Signs to Watch For

Symptoms depend on how fast the fluid builds up. Often, signs appear suddenly — even though the process may have been developing for days or weeks. ⚠️

🚨 Emergency Signs:

• 😵 Sudden collapse or weakness
• 😮‍💨 Difficulty breathing
• 🩸 Pale gums

🟡 Subtle Signs:

• 🐢 Slowing down or fatigue on walks
• 🐷 Pot-bellied appearance (from abdominal fluid)
• 🍽️ Decreased appetite

Breeds like German Shepherds, Golden Retrievers, and Labradors are more prone, but any dog or cat can be affected. 🧬

🔬 Diagnosis

🧪 Tools We Use:

• 📸 X-rays: Enlarged heart silhouette
• 🩺 Ultrasound (echocardiogram): Confirms fluid around the heart
• 🧫 Fluid analysis: Identifies type and potential cause
• 🧪 Blood clotting tests: Rule out toxin-related causes

Sometimes, we cannot identify a clear cause on initial testing. In those cases, repeat testing or monitoring may be needed. 🔁

💉 Emergency Treatment: Pericardiocentesis

This life-saving procedure involves using a needle to remove the fluid and relieve pressure on the heart. Often done with ultrasound guidance, it can result in instant and dramatic improvement in circulation and breathing. 🩹

• 🧵 Often done under local anesthesia
• 🧪 Provides fluid samples for lab testing
• ❤️ Stabilizes patients quickly

Afterward, your pet will be monitored for several hours to check for fluid recurrence or heart rhythm disturbances. 🫀

🏥 Hospital & Long-Term Options

• 💉 IV fluids and oxygen therapy
• 🩺 ECG monitoring for arrhythmias
• 💊 Pain control and comfort care

In rare or recurring cases, a pericardiectomy (removal of the sac) may be performed by a specialist surgeon. 🔧

📉 Prognosis

🚩 If the fluid is blood:

This usually suggests a tumor, often hemangiosarcoma. Sadly, survival is often only weeks to months. Chemotherapy may be discussed, but outcomes remain poor. 💔

🟢 If the fluid is clear or slightly bloody:

Better prognosis, especially if the cause is idiopathic (unknown but non-cancerous). Half of these pets don’t have a recurrence after fluid removal. 🧪

🐱 In Cats:

FIP may be the cause. A promising new treatment for FIP is emerging and may offer hope in some cases. Consult your vet or a specialist. 🧬

📱 Support with Ask A Vet

Facing pericardial effusion can be overwhelming, but you don’t have to navigate it alone. With the Ask A Vet App, you can:

• 💬 Speak with licensed veterinarians 24/7
• 🧾 Track medications, symptoms, and fluid recurrence
• 📅 Get reminders for follow-up diagnostics

Visit AskAVet.com to get help when it matters most. ❤️

🧠 Final Thoughts from Dr Duncan Houston

Pericardial effusion is serious — but quick action can save your pet’s life. Early detection and emergency treatment make a big difference, especially in non-cancerous cases. 🩺

Whether you’re preparing for an emergency, facing a diagnosis, or seeking palliative care options, Ask A Vet is here to support you. 🐾🫀