Could an Injury Have Caused My Dog's Hemangiosarcoma?

We're so sorry. Please be reassured: this was not your fault. Hemangiosarcoma is thought to start from bone-marrow cells that form blood vessels, and breed and genetic factors play a role. No lifestyle factor is known to cause it, and we found no evidence that an injury can. It grows silently for a long time before signs appear, so it was almost certainly already in his spleen well before the picture fell.

These tumors are fragile and often rupture on their own, without any injury. A blow to the belly can cause a blood-filled mass called a hematoma, which can look similar on a scan, but that's different from causing cancer. Your hope is very likely right: the cancer was already there and simply started to bleed.

Thirty-two days after surgery is sadly within the usual range. With surgery alone, most dogs with splenic hemangiosarcoma live about 1 to 3 months, and chemotherapy adds only a few months on average. Choosing not to do chemotherapy was a reasonable, caring decision.

See hemangiosarcoma in dogs and spleen tumors in dogs.

This is general information, not a diagnosis. Please follow your own vet's advice.