WASHINGTON, Aug. 24 - Flesh-eating maggots and bloodsucking leeches, long thought of as the tools of bygone medicine, have experienced a quiet renaissance among high-tech surgeons, and for two days beginning Thursday a federal board of medical advisers will discuss how to regulate them.
Leeches, it turns out, are particularly good at draining excess blood from surgically reattached or transplanted appendages. As microsurgeons tackle feats like reattaching hands, scalps and even faces, leeches have become indispensable.
And maggots clean festering wounds that fail to heal, as among diabetics, better than almost anything else, although their use in the United States has been slight, in part because of squeamishness.
But neither leeches nor maggots have ever been subject to thorough regulation by the Food and Drug Administration. So the medical advisers are being asked to create general guidelines about how they should be safely grown, transported and sold.
Since 1976, the F.D.A. has required that makers of medical devices prove that their products are safe and effective. Those already on the market as of that year had to prove their worth; those invented later had to get approval before marketing.
There are unexplored corners of the nation's medical market, however - no one knows how many, but they are certainly a vanishing few - in which doctors and manufacturers have been doing business since well before 1976 without much notice from the agency. The sale of maggots and leeches is one of those corners.
In addressing it, officials first had to decide which part of the agency had oversight: its biological or device division.
"The primary mode of action for maggots is chewing," said Mark Melkerson, acting director of the Division of General, Restorative and Neurological Devices. "For leeches, it's the eating of blood. Those are mechanical processes." Thus, the agency decided that maggots and leeches were devices, Mr. Melkerson said.
For centuries, doctors used leeches in the mistaken view that they would help balance a patient's body fluids, or "humors." Doctors are said to have drained quarts of blood from an ailing George Washington before he died.
With the development of modern medicine, leeches fell out of favor. But in the 1970's they again became popular, this time with microsurgeons.
When reattaching or transplanting an appendage, these surgeons are often able to stitch together arteries, which deliver blood to the appendage and are thick-walled and relatively easy to suture. Far harder is finding and attaching veins, which collect blood for exit and are smaller and more fragile.
After surgery, with few veins connected, blood tends to engorge the appendage, then to clot, turn blue and - in the worst cases - kill it, said Dr. L. Scott Levin, a Duke University hand surgeon. To buy time for the body to create its own veinous attachments, surgeons use leeches.
Leeches naturally inject patients with a potent chemical cocktail that includes an anticoagulant, an anesthetic, an antibiotic and a substance that dilates blood vessels. This cocktail encourages fast bleeding to empty the appendage of extra blood, reducing pressure and allowing veins to form on their own.
In 20 minutes, a leech is usually engorged and removed, though bleeding from the wound may continue for up to 24 hours. If an appendage is large, several leeches are sometimes used at once, Dr. Levin said, adding, "I'll use one to three leeches every couple of hours."
Leeches are also extraordinarily sensitive to proper blood flow and so can offer immediate feedback on how well surgery went, said Dr. Bruce Minkin, a hand surgeon in Asheville, N.C.
"It won't attach if there's not good arterial blood coming in, and sometimes that tells me that I need to go back in," Dr. Minkin said.
Josh Combs, 17, of Asheville needed leeches to save a thumb that had been reattached after being blown off by a homemade firecracker. His mother, Sherry Combs, said she was startled when Dr. Minkin told her what he was going to do.
"I said, 'Can you tell me what you just said again, please?' " Ms. Combs recalled in an interview.
Ms. Combs has two phobias: mushrooms and leeches. So she stood away, over by the door, while a leech was applied to her son's thumb.
"I was afraid he would wake up suddenly and see a leech stuck to his hand," Ms. Combs said. Josh later did just that, with another leech, which he named Fred.
As for maggots, they are unparalleled in their ability to clean festering, gangrenous wounds. For diabetics and others whose wounds fail to heal, maggots, pressed into dying flesh by wire-mesh bandages, can save a limb and speed healing.
Primitive tribes in Australia, the hill people of northern Burma and the Mayans of Central America are known to have used maggots to clean wounds. Napoleon's surgeon in chief noted their effects.
And during World War I, a doctor described seeing two soldiers who had been left wounded on the battlefield for days. When their clothes were taken off, thousands of maggots were found in their wounds. Once the maggots were removed, the doctor was astonished to find clean, pink, living flesh. That doctor, William Baer of the Johns Hopkins School of Medicine, became maggots' modern medical champion.
Another oddity whose regulation will be discussed by the advisory board starting Thursday is bone wax. That product - made of beeswax, olive oil and phenol - has long been used by surgeons to stop bleeding in bones cut during surgery, since neither cauterization nor pressure works well on them. And it is sometimes used to discourage unwanted bone regrowth, said Dr. Glenn Pfeffer, director of foot and ankle surgery at Cedars-Sinai Medical Center in Los Angeles.
"I just had a spur on my foot taken out," Dr. Pfeffer said. "And the surgeon applied bone wax to the cut ends to make sure it doesn't re-form."