This article is part of our Pets special section on scientists’ growing interest in our animal companions.

Heather Massey brought Ladybird to the veterinarian when the 9-year-old mutt began having seizures. A scan from an M.R.I. machine revealed bad news: brain cancer.

With the prognosis grim, Ms. Massey decided against further treatment at the animal hospital near her home in Athens, Ga., and Ladybird died four months later. The M.R.I. scan and related care had cost nearly $2,000, which Ms. Massey put on a specialty credit card she had learned about at a previous vet visit.

That was in 2018. She is still paying off the debt, with more than 30 percent interest.

“Could I afford to do that? Not really,” said Ms. Massey, 52, who is disabled and does not work. “Was it worth it to me? Yes.”

Ms. Massey’s experience illustrates the expensive new realities of owning a pet. For decades, veterinarians typically operated their own clinics, shepherding generations of pets from birth to death. They neutered, vaccinated and pulled thorns from paws and noses. When animals became seriously ill, vets often had little to offer beyond condolences and a humane death.

But in recent years, as people have grown more attached to their pets — and more willing to spend money on them — animal medicine has transformed into a big business that looks a lot like its human counterpart. Many veterinary offices have been replaced by hospitals outfitted with expensive M.R.I. machines, sophisticated lab equipment and round-the-clock intensive care units. Dogs and cats often see highly trained specialists in neurology, cardiology and oncology.

This high-tech care has spurred a booming market. Veterinary prices have soared more than 60 percent over the past decade, according to federal statistics. Private equity firms and large corporations have bought hundreds of facilities around the country, an acquisition spree reminiscent of the corporate roll-ups of doctors’ offices.