Leeches May Be Making a Medical Comeback

Jan. 21, 2004 -- They may be slimy, blood sucking worms, but leeches can help you heal, and may also ease your knee pain.

The three-jawed creatures have long had a role in medicine, dating to at least as far back as 1500 B.C. when ancient wall art shows Egyptians applying the worms to patients for bloodletting. In the 1800s, leeches became a widespread treatment preferred by doctors throughout the United States and Europe.

But by the late 19th century, modern medicine mostly abandoned the worm in favor of less grotesque pharmacology.

Now the leech appears to be making a comeback.

In a recent study published in the journal, Annals of Internal Medicine, Andreas Michalsen of the University of Duisburg-Essen in Germany, describes how placing four to six leeches on an aching knee suffering from osteoarthritis eased pain better than the leading topical anti-inflammatory treatment.

The process involved 70 minutes of sucking (about the time it takes a leech to fill its belly) on a daily basis for up to 90 days. Those who submitted their knees to the worms reported they felt more relief for the first seven days than those who applied the topical cream twice a day. Michalsen says those who underwent the therapy for 90 days also felt relief, but since there were fewer patients who were treated this long, the results weren't statistically significant.

"The pain relief was still evident," Michalsen said, adding that most of the patients were not put off by the leech treatment, but actually found it "fascinating."

While the findings were promising, the author and others admit that the leeches' benefits aren't yet proven.

The Placebo Problem

One problem, says Marc Hochberg of the University of Maryland School of Medicine, is that this was not — and could not be — a blind study. Those who were receiving the leech therapy knew it and those who were not knew it too.

This makes it impossible to avoid the so-called placebo effect — when patients who know they are receiving treatment rate their recovery as better simply because they expect it to be.

The only way to avoid such skewed results, says Hochberg, would be to "fake" leech therapy. That may seem impossible, but he points out his lab has found a way to fake acupuncture treatment for studies. Rather than sticking in the needles, the doctor only uses the needles to tap the surface of the skin of those patients who are in the control group (the ones not receiving the actual treatment).

"The patients naive to the procedure don't know the difference," he said.

Of course, it's difficult to imagine what might make up fake leech therapy and Hochberg admits he's stumped.

"I don't see any way of blinding it," he said.

Also, to be sure the leeches are true healers, Hochberg argues it's important that scientists identify their trick. So far 30 chemicals in the leech's saliva have been identified but scientists don't yet know what chemicals in the worm's saliva acts as anti-inflammatories to decrease swelling and relieve aching.

While the ability of leeches to ease osteoporosis may still be in question, their effectiveness in treating wounds from plastic or reconstructive surgery is proven and fairly widespread.

Master Healers

Every year thousands of people subject themselves to the worms' bloodsucking to relieve blood clots and revive blood flow. Congested blood veins are a common problem following procedures such as breast reconstruction, limb or finger reattachment or neck reconstruction, where tissue is moved from one place to another.

To tackle the problem, surgeons in the 1980s began bringing the leech back to modern medicine. In a procedure that often involves a team of several medical staff, handfuls of leeches are placed on the patient's post-surgical wound and allowed to suck.

As individual worms ingest their fill, they slip off and are replaced with hungry leeches by the staff. Medical assistants also monitor the worms to make sure they only suck where they're needed.

"The leeches have their own agenda," explains Nadine Connor, director of the division of otolaryngology at the University of Wisconsin-Madison. "They just want to fill their bellies with blood. They need to be watched and make sure they stick where they're supposed to be."

The procedure may seem repulsive, but Connor reports the leeches really do the trick.

She explains leeches effectively drain clotted blood from the wounds while anti-coagulating agents in the leeches' saliva keep a patient's blood from forming further dangerous clots. What's more, they release an anesthetic from their fangs (each of the worm's three jaws hosts about 100 teeth), so the process is pain-free.

The Mechanical Leech

Although the leech treatment works for this purpose, Connor and her colleague, Gregory Hartig, a surgeon at the University of Wisconsin-Madison, have sought an alternative that can achieve the same result — minus the "yuck factor."

"Patients are willing to do just about anything, but they don't like the leeches," said Connor. "You make a tough situation worse by using these creatures."

In place of the worm, Connor and Hartig have helped build a mechanical version of the leech that removes clotted blood and helps promote healing. The blood-sucking machine looks nothing like the worm. Instead, it is a bell-shaped glass cup with a protruding porous tip that's implanted just under the skin. The tip rotates to prevent clotting and releases the anti-clotting agent heparin to keep blood flowing.

The machine is still in testing and Connor estimates it will be at least a couple years before it's offered up as a leech alternative. When it does become available, Connor hopes the benefits of the leech could be offered even to the squeamish — sans the worm. And, she's sure about one thing:

"When we name it, we're definitely not going to call it a mechanical leech," she said. "That would defeat the whole purpose."