Who knew 50ml of fluid had accumulated in her chest? My cat was diagnosed with hemangiosarcoma, and I learned "key points for post-operative follow-up care."

Hemangiosarcoma, a cancer originating from the cells that form blood vessels, is a malignant tumor often seen in dogs, but it is rare in cats. Yet, my own cat, Gigi, developed this rare disease and has since passed away.

However, I learned so much during our battle with this illness. Based on my personal experience, I would like to share the "warning signs to watch for when consulting your veterinarian" and "key points for early detection" when monitoring hemangiosarcoma.

Removing a hemangiosarcoma from the intestine... The high risk of "metastasis"

In Gigi's case, the hemangiosarcoma was in his intestine. The process to reach a definitive diagnosis was long, so if you would like to know the details, please see this link.

After the surgery, the veterinarian told me, "I removed what I could, but I cannot guarantee that it was entirely cleared." He also added, "Since the tumor was bleeding before removal, there is a high possibility that cancer cells have entered the bloodstream and metastasized somewhere," which left me feeling hopeless.

I just wanted him to live as long as possible, comfortably. Because there is so little known about feline hemangiosarcoma due to the lack of cases, I also dared to hope that perhaps my prayers for "remission" would be answered.

Perhaps I had to shift my mindset like that just to keep myself from falling apart.

From then on, I took Gigi to the animal hospital once a month for regular ultrasound check-ups.

I am grateful that the veterinarian took about 15 minutes each time to carefully examine other organs prone to metastasis besides the intestines. During these check-ups, he would show me the ultrasound and explain his condition in an easy-to-understand way.

According to the vet, in dogs, hemangiosarcoma often metastasizes within about two months even after the tumor is removed. Perhaps that is why he would praise us every time, saying, "He is doing very well," and "I don't see anything suspicious in the spleen or kidneys, which are common sites for metastasis."

However, there seemed to be something like inflammation around the area where the intestine was resected. Since the ultrasound could not definitively confirm it as a tumor, the vet would say, "I apologize that I cannot be certain, but it could be residual tumor tissue or post-surgical inflammation."

I was worried about that inflammation, but since he had energy, an appetite, and was living quite normally, I consulted with the vet and we decided to continue monitoring him through regular check-ups.

However, I was told to bring him in immediately if I noticed even the slightest change, such as a loss of appetite, frequent vomiting, or blood in his stool.

Going to the hospital due to concerns about coughing and cries when held

About three months after the tumor removal surgery, I was told during a check-up that he had a small amount of ascites (fluid in the abdomen). It wasn't a large enough amount to require draining, and there were no signs of metastasis in other organs.

Since he still had his appetite and energy, and there were no visible changes in his daily life, we decided to continue monitoring him with ultrasounds while carefully checking the state of the ascites.

However, during Golden Week in 2025, Gigi coughed, which was unusual, and I grew worried. Actually, before his hemangiosarcoma was diagnosed, Gigi had coughed occasionally, so I thought, "This might be metastasis..."

He still had his appetite and energy, but when I picked him up and hugged him tight, he would cry out "Nkyah!"—whether from joy or pain, it was just like it was right before his hemangiosarcoma was first diagnosed.

X-ray reveals "50ml of pleural effusion"...

My anxiety grew, so I went straight to our regular vet. I began by saying, "I'm sorry for being overprotective, but..." and described his symptoms; he started with the usual ultrasound.

The ultrasound showed no obvious abnormalities. But the vet said, "I don't think there's a problem, but let's take an X-ray just in case."

And that revealed that there was fluid accumulation in the chest (pleural effusion). Honestly, when I heard that, I thought, "The ascites could be seen on the ultrasound, so shouldn't pleural effusion be visible too...?" and I asked the vet why it wasn't discovered earlier.

The vet explained, "Along with the spleen, kidneys, and the area around the intestine where we operated, we were also checking chest organs like the heart, but pleural effusion is hard to spot unless you are specifically looking for it..." Hearing that, I was honestly angry, thinking, "I wish you had checked more thoroughly."

However, as I watched the speed at which the fluid accumulated afterward, my feelings changed. In Gigi's case, when we went to have the pleural effusion drained once a week, about 100ml would accumulate, and toward the end, it was more than we could manage even with weekly visits.

However, the amount drained when I first noticed the changes and had the X-ray taken was only about 50ml. I began to think that perhaps it wasn't an oversight by the vet, but that it was just the point when the fluid had started to accumulate.

It is important to check "areas you aren't focused on" during regular exams

Through this experience, I learned that after a cat has surgery for hemangiosarcoma, it is important to ask the vet for as thorough an examination as possible—not just of the surgical area, but also for early detection of abnormalities in organs further away.

Since Gigi’s hemangiosarcoma was in his intestine, I was concerned about the small amount of ascites, but ultimately, it was the pleural effusion that took his life. It was an abnormality in a completely different area than what I was worried about.

(*Incidentally, the ultrasound did not show any obvious metastasis to the lungs.)

Of course, veterinarians are professionals in animal medicine, and they do their best to help with early detection of whole-body abnormalities even if the owner doesn't say anything.

However, as the owner who is always with your cat, there are always changes you will notice that others might miss. At such times, do not hesitate to ask them to examine your cat's body from a different angle than usual—it is very important.

Also, during regular check-ups, asking the vet specifically, "What kind of changes should I look out for that would warrant an immediate visit?" might help you better identify what constitutes a "change" yourself.

Being able to notice subtle changes and get to the hospital quickly can lead to extending their life, even if only for a little while.

It is important to not only keep an eye on the surgical area you are worried about but also keep in mind that abnormalities might be occurring in areas you assume are "healthy." I feel that this perspective is important when fighting malignant tumors, not just hemangiosarcoma.

Currently, there is still very little information about feline hemangiosarcoma. While there are individual differences in the site of onset and symptoms, it is my wish that by gathering more personal experiences, more cats can achieve remission and more owners can feel at peace with their journey.

...I think my cat essays will likely continue to cover rather heavy topics like fighting illness, pet loss, and cremation for a while. I apologize if it feels "too heavy." But I believe this is what "lifelong care"—staying by their side until the very end—is truly about, so I want to carefully share what I experienced and what Gigi taught me.

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