Washington ? It’s a scene familiar from TV dramas, a helicopter racing an ice chest holding a precious donated organ to waiting surgeons. But instead of storing kidneys on ice, a few transplant centers hook them to complex machines that pump special fluids through the blood vessels.

To pump or not is controversial, because pumping is difficult and expensive, but supporters say it keeps kidneys healthier longer and could increase the nation’s short supply by better predicting when older, sicker donors’ kidneys are usable.

Now a major new study — with a portable pump that promises to be easier to use — is beginning that may finally settle whether transplant centers should keep more kidneys out of the ice chest.

“Maybe we can use kidneys we otherwise might have discarded,” said Dr. Robert Montgomery of Johns Hopkins University, who this week begins the government-funded re-search to test that theory.

More than 55,000 Americans are awaiting kidney transplants. Only about 14,000 will get them this year.

Once a kidney is donated, most are stored in a cold preservative solution on ice for up to 24 or 30 hours before transplantation into a waiting patient.

About 12 percent of donated kidneys are hooked up to complex perfusion machines that pump different fluids containing nutrients and preservatives through the blood vessels, much as blood would pump.

Cold, hard facts

Does pumping work better than ice? The Hopkins study will provide the first good direct comparison. But:

• The longer it’s stored, the more likely a kidney won’t start working right away once it’s transplanted, which requires expensive post-surgery dialysis and increases the risk of organ rejection.

Roughly one in four kidneys will have delayed function. Centers that pump kidneys report far lower rates, less than 5 percent at Ohio State University Hospital.

• Because of shortages, about 15 percent of transplanted kidneys come from less-than-ideal donors — older people or those with health problems such as high blood pressure, and those whose hearts quit beating up to half an hour before their organs were recovered.

The pump helps predict which of those kidneys are too damaged to use by measuring how easily fluid moves through them. The Gift of Life Donor Program in Philadelphia, the nation’s largest, has cut in half the number it discards since pumping less-than-ideal kidneys began two years ago.

• Other research suggests pumping increases the amount of time a kidney can be stored without damage, enabling easier coast-to-coast shipping.

Cost considerations

But pumping adds at least $2,000, by some estimates up to $5,000, to a transplant’s cost. It takes a specially trained technician to hook a kidney to the pump and do the required monitoring. And when shipping a kidney inside the pump, even supporters call today’s machines cumbersome.

“If cost and logistics were no problem, I would pump kidneys,” said Dr. John Fung, transplant chief at the University of Pittsburgh Medical Center, a leading transplant center that so far has decided not to pump.

Enter the Johns Hopkins study. It will randomly assign 300 donated kidneys to either standard cold storage or pumping with a new-generation machine, Organ Recovery Systems’ LifePort Kidney Transporter.

Kidney pump technology isn’t new — first-generation pumps were popular decades ago until cheaper ice storage improved. The LifePort claims to improve on older pumps by being easier to handle, more the size of an ice chest but fully automated instead of needing manual monitoring.

LifePort’s maker argues the changes should encourage more kidney pumping and thus significantly increase the number of usable organs, and pumping pays for itself with less post-surgery dialysis. The Johns Hopkins study may help tell if all that is true.

“The real challenge, frankly, isn’t kidneys,” added Gift of Hope chief executive Howard Nathan. He points to organs that can’t be stored on ice nearly as long — livers last 16 hours, hearts a mere four, the reason a donated heart is often raced to a recipient via chartered jet.

Scientists already are working to make pumps for other organs.