What Is This Lump at My Pet’s Incision Site?

Noticing a lump near your cat’s or dog’s surgery incision can be alarming — but in many cases, it’s completely normal and part of the healing process. 

Author: Sara Castillo | Practice Manager

After a spay, some pets develop a small, soft swelling under the incision. This is often what’s known as a seroma, and while it can look concerning, it typically resolves on its own.

At Spay Neuter Vets, we want you to feel confident in knowing what’s normal, what’s not, and when to reach out for follow-up care.

What Is a Seroma?

A seroma is a small collection of clear fluid that can form under the skin after surgery.  It’s the body’s natural response to trauma and healing of the dead space left in the subcutaneous layer after a procedure.  

As Dr. Kooyman explains:

“A lump under the skin at the incision site post-spay is likely a seroma (a localized buildup of serum and lymphatic fluid). This occurs post operatively whenever there is trauma to the tissue and a creation of dead space.  The size of the seroma can increase with movement and activity.  Most seromas are self-resolving as the body reabsorbs the fluid over the course of several weeks.  If the lump increases in size or shows signs of infection (redness, discharge, heat, or pain), or your pet becomes lethargic or loses appetite, please contact us.”

What Does a Seroma Look and Feel Like?

Seromas can vary from pet to pet, but here’s what’s typically normal vs. concerning:

To help prevent seromas:

• Keep your pet calm and rested for 10–14 days after surgery. Consider adding post-op sedation medication to your pet’s surgical services when you book your appointment with us!

• Avoid running, jumping, or rough play until cleared by your vet.

• No baths or wetting the incision until fully healed.

• Use an Elizabethan collar (cone) as directed to prevent licking or chewing.  While licking and chewing will not contribute to a seroma, it will lead to infection of the incision site.

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Worry about what should and shouldn’t be done after your pet’s spay/neuter surgery, read more about it in our article: Aftercare for Spayed/Neutered Dogs and Cats - The Post-Surgery Recovery Guide.

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What You Can Do at Home

If your dog’s or cat’s incision looks sealed and there’s just a soft or slightly firm lump underneath:

• Apply a warm compress (not hot) for 3–5 minutes, 1–2 times daily, if your pet allows.

• Continue to limit activity to avoid further irritation.

• Expect the swelling to gradually shrink over 2–4 weeks.

If the lump gets bigger, becomes red or painful, or your pet seems unwell — it’s time for a recheck.

When to Contact Us

If your pet was spayed/neutered at our facility, reach out if you notice:

• Redness, heat, or increasing pain around the incision

• Drainage, bleeding, or foul-smelling discharge

• Swelling that rapidly grows or changes in shape

• Lethargy, loss of appetite, or changes in behavior

• An incision that looks open, moist, or unusual

If you're unsure, we’re happy to take a look. Text a clear photo to 678-834-0777 along with a brief description of what you’re seeing. Our team will review it and let you know whether everything looks normal or if a recheck is recommended.

The Bottom Line

Most small, soft lumps after surgery are simply seromas — a normal part of healing that generally resolves with rest and time. Still, any sudden changes or signs of discomfort are worth checking. We’re here to help ensure your pet heals safely and comfortably.

We’re Here Every Step of the Way

Whether you’re navigating recovery or scheduling surgery for another pet, our team is committed to offering clear guidance, compassionate care, and ongoing support.

Ready to book your pet’s spay or neuter?

 Experience the Spay Neuter Vets difference — where your pet’s safety and comfort always come first.