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October 2001
Vol. 10, No. 10,
pp 47–48.
 
 
 
Health Perspectives
The return of the leech

A medical marvel rises from both the swamp and the pages of history.

NATIONAL LIBRARY OF MEDICINE
It sounds like a scene from a cheesy horror movie. A patient awakes from surgery to find a slimy leech, big as your thumb, feasting on the tender flesh of his nose. Yet that really happened five years ago to William Rambo, a retired electrical engineering professor who now lives just outside Denver.

Rambo didn’t panic because his surgeon, Richard Goode of Stanford University Medical Center, had briefed him on the benefits of the fabled bloodsuckers. Rambo had lost most of his nose to a series of skin cancer surgeries, so Goode used a flap of skin from Rambo’s scalp to rebuild the nose. When the flap developed a common complication—insufficient blood drainage that can kill the tissue—Goode called for leeches. Feeding in shifts, about 20 leeches drained the pent-up blood and saved Rambo’s reconstructed nose. Rambo, now 85, says two good things came from playing host to the little vampires. “I got my own room in the hospital,” he says, “and I got a fine new nose.”

Thousands of patients share his admiration for the leeches’ unique talents. Long dismissed as quackery, the use of leeches has returned to the medical mainstream over the past 20 years. Plastic and reconstructive surgeons depend on leeches, predominantly Hirudo medicinalis, to drain excess blood and prevent clotting after operations to reattach severed fingers, lips, ears, or other body parts. Surgeons may also turn to leeches after they transplant a flap of skin from one part of the body to another, as in Rambo’s case, or perform other kinds of plastic surgery. Without leeching, blood clots often kill the repaired or transplanted tissue.

Leeches provide other benefits as well. Scientists are working to harvest the bounty of chemicals synthesized by these cousins of the common earthworm. One leech-made molecule, the powerful anticoagulant hirudin, won FDA approval in 1998. Medical researchers are now testing hirudin’s usefulness against angina and heart attacks, and other chemicals from leech saliva are under study.

Back from Oblivion
Leeching has a long and grisly history. The documented use of leeches in medicine stretches back to Greece in the 2nd century B.C.E. The bloodsuckers remained the physician’s standby throughout the Middle Ages—in fact, the modern word “leech” derives from the Old English word for “physician”— but during the 18th and 19th centuries, the practice boomed to a point that has been called “leechmania”. Believing that excess blood caused disease, doctors prescribed leeches for almost every ailment, from headaches to hemorrhoids. A leech enthusiast might treat tonsillitis, for example, by securing a leech with thread, lowering it into the patient’s throat, and allowing it to feed on the swollen glands. To the tremendous relief of patients, scientists discredited the rationale for leeching—that blood loss was therapeutic—and the practice fell out of favor in the late 1800s.

So why did doctors resurrect this antique treatment after almost 100 years? “There’s a very specific scenario when they are perfect,” says surgeon Matthew Concannon of the University of Missouri, Columbia, who began using leeches in 1992. The return of leeches coincided with the development of techniques for microvascular surgery.

Surgeons worked out a method for stitching bisected arteries and veins together under a microscope, thus making it possible to reattach severed tissues and to transplant skin flaps. However, many of these operations failed because of a problem called venous congestion, inadequate blood drainage from the reattached or transplanted tissue. It is fairly easy to rejoin severed arteries that carry blood into the finger, says plastic surgeon Jeffrey Friedman of Houston’s Baylor College of Medicine, but it is difficult to find and reconnect the veins that drain blood from the finger. As a result, even the most skilled and careful surgeon may not be able to link all the veins, and blood will begin to pool within the finger. Unless this buildup is relieved, clots may form and cut off blood flow into the finger, eventually killing it. Swelling and a blue or purple color signal venous congestion. When these symptoms appear, leeches slither to the rescue. (For several graphic examples, visit Leeches USA.)

Serving as a substitute vein, a leech draws off blood before it can coagulate, thus keeping the tissue alive until new veins grow—usually within 5–6 days. Over the years, doctors have unsuccessfully tried a host of seemingly more advanced treatments to achieve the same thing, from blood thinners like heparin to slicing the skin to promote bleeding. “Nothing is as effective as a leech,” says Donald Mackay of Pennsylvania State University College of Medicine who has been prescribing leeches since 1988.

Besides their blood-draining skills, leeches have other virtues. Although a leech only feeds for 20–30 min, it injects anticlotting chemicals that can keep blood leaking from the wound for hours. Thus the benefits of a leech bite continue long after the animal has dropped off. Leeches are also cheap to buy ($7.50 each) and easy to maintain. They can survive for months in a dilute saline solution without feeding.

Of course, roving annelids with a taste for blood do pose some unusual problems for doctors, nurses, and patients. For one thing, they must be monitored carefully, because after feeding they will seek a dark place to rest and digest. Roaming leeches can enter a patient’s nostrils, mouth, or other orifices. Two of Rambo’s leeches escaped when he fell asleep—nurses later found them scaling the wall of his room. As they drink, leeches can also introduce bacteria into the patient’s bloodstream. To prevent infection, most surgeons dose their patients with broad-spectrum antibiotics such as cephalosporin or ciprofloxacin. Leeches may also cause prolonged bleeding that necessitates blood transfusions. As with any other medical procedure, the decision to use leeches involves weighing the costs and benefits, says Mackay.

The Painless Bite
Ultimately, of course, patients make the call. You might think that squeamish patients would be a big obstacle to leech use. Not so. Almost no one refuses leeches out of fear or disgust. Together, Friedman, Mackay, and Concannon have more than 30 years of experience with leeches. Of the hundreds of patients they have operated on, only one refused to be leeched. There aren’t many options, says Friedman. For someone whose finger has just been reattached, he says, the choice is brutally simple: “We can cut your finger off again or use a leech.”

However, Mackay has seen a much more positive reaction. Patients don’t just endure leeches the way they might endure, say, a colonoscopy. They like leeches, he asserts. “Patients and nurses become tolerant and quite fond of them,” he says. Some of his patients have even given their leeches nicknames. Rambo concurs. He had no qualms about the treatment and enjoys reminiscing about his two leeching sessions in 1996. The bite was painless, he recalls, and the leeches were unobtrusive, “though you can feel them moving around.” His take on the episode: “It was fascinating.”

Learning from Dr. Leech
Many of the benefits of leech therapy derive from the chemicals that the animals secrete into the wound. Leeches are excellent chemists, manufacturing a number of molecules that keep their meal of blood flowing. The most-studied of these is hirudin, a small protein composed of 65 amino acids. Hirudin is a potent anticoagulant because it inhibits the protein thrombin, a key molecule in the cascade that leads to blood clotting. Scientists are still exploring the possible applications of hirudin. One promising use is as an alternative to heparin, the standard drug for treating blood clots. The FDA approved a recombinant form of hirudin, known as lepirudin, for patients who suffer complications from heparin.

Lepirudin may be superior to heparin for preventing heart attacks, though the jury is still out on this question. For example, a study reported in the Lancet showed that angina and heart attack patients who were treated with lepirudin were about 14% less likely to die or have a subsequent heart attack than patients who received heparin. However, the same study also found a 71% greater risk of bleeding in the patients treated with lepirudin. Because lepirudin is more expensive than heparin and provides only a modest advantage, its use may be limited. However, further studies of leech saliva may turn up new anticlotting chemicals or other potentially valuable molecules.

Future Leeches?
They’ve already been booted from medicine once and have an evil reputation—thanks mainly to movies like The African Queen, in which hardboiled Humphrey Bogart starts blubbering when attacked by a few leeches. But for the moment, the leech’s position as surgeon’s helper seems secure. Nothing else works as well. Perhaps the biggest future threat will be an artificial leech—several types have already been invented, and others are under development. However, it’ll be a huge challenge to make a device that’s as effective and cheap as the real thing. Concannon isn’t impressed by the models he’s seen so far. “I haven’t run across one that makes me think, ‘Let’s replace the leech.’”


Mitchell Leslie is a freelance writer living in Albuquerque, NM. Send your comments or questions regarding this article to tcaw@acs.org or the Editorial Office 1155 16th St N.W., Washington, DC 20036.

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