Modern Leeching

Modern Leeching Photo Credit: Paul Paquette, via Wikimedia Commons

In the 1800's, leeches used to be the state-of-the-art medicine. But even today, their blood-sucking abilities are still in demand by doctors. You'll hear some reasons why in this Science Update.


Tales of the modern leech. I'm Bob Hirshon and this is Science Update.

Bloodletting is no longer the cure-all remedy it once was. So Heidi Haugen of Sacramento, California, wonders why a form of that ancient science can still be found in state-of-the-art hospitals.


Why are leeches used in modern medicine?

Well, Heidi, we asked Bill Lineaweaver, a surgeon at the University of Mississippi Medical Center. He says leeches are often the best option for safely removing congested blood from a wound.


Leeches are used in modern medicine because they work. They're an extremely effective artificial vein in certain situations where uh, a body part such as a finger has been replanted after an amputation, but only the arterial side is working. The, the leech then serves as an artificial vein by drawing off the excess blood or the congested blood, until the person can actually grow back small, venous capillaries.

He says some modern techniques for drawing off excess blood result in too much blood loss. Leeches, though, are considered to be a cost effective, more efficient, and less damaging alternative.

If you've got a question along scientific vein, call us at 1-800-WHY-ISIT. If we use it on the show, you'll get a free Science Update mug. For the American Association for the Advancement of Science, I'm Bob Hirshon.

Making Sense of the Research

Picture this: You're chopping a steak with a big meat cleaver and—wham!—off comes your right index finger. Picture putting the finger in a jar and taking it with you to the hospital. Now picture a doctor carefully sewing the finger back on, and within hours the finger is blue and swollen with blood.

Grossed out yet? Good! Because now you can picture sticking a hungry leech on the end of that finger and—presto!—the finger returns to a nice healthy pink. As Lineaweaver explains, that's one of the leech's greatest talents. When a finger or thumb is reattached, it's relatively easy to hook up the arteries, because they're thicker and tougher. Veins, on the other hand, are fragile and crumple up easily. So, until new capillaries can to re-connect these damaged veins, what you end up with is blood with a one-way ticket into a reattached finger. With no veins to carry it back out, the finger swells up and chokes itself off with blood clots.

Leeches are ideal in this situation because they suck the blood slowly and steadily. (If you drain the blood too fast, you may as well not have bothered to reattach the finger.) To drain blood at just the right rate without using leeches, surgeons sometimes turn to an even more disgusting (and less effective) procedure that involves ripping off a fingernail and scraping the nail bed raw so it bleeds at a slow and steady rate. Given the choice, most doctors—and patients—opt for the leeches.

Plus, leeches secrete natural anticoagulants that prevent the blood from clotting. One of these chemicals, hirudin, is so powerful that it's being studied as a possible therapeutic drug for people who have had heart attacks and strokes. These chemicals allow the wound to bleed slowly even after the leech has been removed, while the patient's new veins are still forming.

Leeches have been used in medicine for over 2,500 years. They were more popular in earlier times because it was widely thought that most diseases were caused by an excess of blood. As recently as the 19th century, leeches were used to treat everything from tonsillitis to hemorrhoids. You can imagine what both of those treatments involved.

Today, their use is more limited, but in some circumstances, they're still the best option. Plus, they're cheap (usually under $7 per leech). One of the few disadvantages is that they often try and hide under a patient's covers after they've been used. You can't blame them: they've just eaten several months' worth of food, and they're ready for a good long nap.

Now try and answer these questions:

  1. Why are leeches still used in modern medicine?
  2. Why is bleeding a necessary part of a re-attachment procedure?
  3. What are some uses for leeches that are no longer in favor?
  4. Can you think of other medical practices that have not changed very much in a fairly long time? Do you think they need to be changed? Why or why not?
  5. Some medical research involves developing state-of-the-art drugs and high-tech machinery for new treatments. But there are also a number of doctors who are studying ancient medical practices from a variety of cultures, to see if these treatments really work. Do you think medicine should primarily focus on one or the other, or on a combination of the two? What are the advantages and disadvantages of each?

For Educators

This Leeches fact sheet from the Australian museum contains a variety of basic leech information.

Read this National Geographic news item Blood-Sucking Machine May Put Leeches Out of Work about a machine that aims to compete with leeches.

Medieval M.D. gives you the opportunity to diagnose and treat illnesses as if you were a medieval physician.

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