Deathly ill, Harley was marinating in his own toxins. The 4-year-old cat's kidneys had stopped performing their vital blood-cleansing function.

The orange tabby from Jordan - his owner was a diplomat in Washington - was carried into the dialysis suite limp, eyes half-closed and glazed over. The veterinarians and other staff at the University of Pennsylvania were already masked and gloved. They hooked Harley up.

Penn's Matthew J. Ryan Veterinary Hospital is one of a dozen dialysis centers nationally (four are on the East Coast) and the closest to Washington.

Short-term, life-saving hemodialysis is pretty much the same in cats and dogs as it is in people, but on a smaller scale. The kidneys have failed due to blockages, poisons, infections, or diseases; tubes carry blood laden with toxins to a machine that filters it and sends it back into the body.

Most human patients are long-term, in chronic renal failure, requiring dialysis a few times a week for life. For pets, it is only a temporary fix: typically six to eight sessions over a couple of weeks, an attempt to buy time so the kidneys have a chance to heal.

Even so, the odds are not great.

"On average," said J.D. Foster, the veterinarian who heads Penn's program, "we save about half of those patients who would be dead without our work."

Half the survivors will require medications and special diets, often for years. They also will have cost their owners about $750 a session - $5,000 to $7,000 by the time they are done. The 1 percent to 2 percent of owners who have pet insurance will discover reimbursements are capped at far less.

Not that the money matters, at least to those who can afford it.

Foster recalls his youngest patient, an 11-week-old Norwich terrier named Manny. His kidneys and liver ravaged last year by the lethal bacterial infection leptospirosis, he arrived "a gelatinous blob." The soft-spoken, professorial vet smiles as he displays Manny's first-birthday picture - complete with party hat - on his phone.

Then there was Yum Yum. Though she had won best of breed at the 2013 and 2014 Westminster Kennel Club Dog Shows, the bull terrier was not so lucky in health. Dialysis couldn't pull her out of acute kidney failure last fall; she succumbed after five treatments.

Harley, the Middle Eastern tabby, came in a few weeks earlier. Things looked bleak as he awaited his third dialysis hookup. It had been two days since his last treatment, and his dying kidneys hadn't produced urine in nearly a week. Over the next several hours, his blood was flushed through the machine almost 40 times. By the second hour, he had regained enough vigor to try to push off his oxygen mask.

Meanwhile, he snoozed, face settled onto the furry, stuffed green snake placed before him by Holly Brooks, a veterinary student.

"He loves to rest his chin on things," she said.

Another thing Harley seems to love is the taste of lilies. Especially popular in the spring, lilies are the bedrock of mixed floral arrangements, and are common as indoor potted plants and in outdoor gardens.

Cats will readily ingest lilies, which contain toxins that demolish their kidneys. Even a nibble can cause death within three to five days. Owners may not even have noticed their flowers were disturbed.

"We've seen sick cats come in with just the pollen on their faces," said Foster, whose clinic's walls, next to the hospital's intensive-care unit, are festooned with photos from grateful owners.

There is no test for lily toxicity and often no proof of what was involved. Harley, for example, was living in a hotel where lilies - or other poisons - could have come in and out on a cleaning cart.

The cause didn't matter. After Harley spent a few days vomiting, sluggish, and refusing to eat, his vet ran blood tests and found his kidneys were not working. He sent him to Penn.

Dialysis actually began in dogs, experimentally, in 1913. Although the goal was to treat people, that didn't happen for several decades. Dogs were forgotten.

Veterinarian Larry Cowgill is credited with expanding the procedure back to animals in the early 1970s, during his residency at Penn Vet.

The only machines were for humans. "We had pieces of junk," Cowgill recalled, "that we put together as a Rube Goldberg experiment."

He moved to the University of California, Davis, where he developed the world's first veterinary dialysis program in 1990. Then Foster, after graduating from Penn Vet, trained in hemodialysis at UC-Davis and brought it back to Penn in late 2012.

Cats make up nearly 70 percent of cases here (nationally, they are evenly split with dogs). The imbalance is because Penn is the only veterinary hospital in the U.S. with active programs in both dialysis and feline kidney transplantation.

The transplant program started in 1998, after surgeon Lillian R. Aronson arrived, also from UC-Davis; 151 cats have received kidney transplants since then.

The separate dialysis program has given 180 treatments to 48 dogs and cats in 21/2 years. The addition of another machine in October allows two patients to be dialyzed at the same time.

In some poisoning cases, it can be a once-and-done fix.

That's what happened with Penn's first patient, a 16-month-old German shepherd named Sophie. Contractors working on Valarie Hiscock's home in Wynnewood saw Sophie lap up what probably was water laced with antifreeze.

Hiscock got her to the Ardmore Animal Hospital in 20 minutes. Her stomach was pumped, and she was sent on to Penn, where her blood was purged of any toxin that might have been absorbed.

"She is a healthy dog!" Hiscock said last week.

Penn has used dialysis to treat poisonings ranging from grapes and Aleve (both in dogs) to chemotherapy overdoses (in cats).

"Toxicities are wonderful," said Foster, "because we can filter out in a few hours what would normally take the body three days to get rid of."

He vividly recalls Holden, a Rottweiler mix that arrived comatose last year after swallowing an entire bottle of ibuprofen. He awoke during dialysis and was able to walk back to his cage on his own.

Harley did not make the trip from Washington soon enough for that. He needed 10 dialysis sessions over four weeks, but eventually, his kidneys took over, and he even got off most of his meds. Five months later, he seems to be thriving.

"He may never return to completely normal [kidney] function," said Robert Justin, his vet in Leesburg, Va., where Harley gets regular blood work. "Time will tell if he continues to recover."

Joan Capuzzi is a small-animal veterinarian in the Philadelphia area. jpcapuzzi@outlook.com.