Leeches are still used in medicine—yes, really. Here’s why.

Leeches are still used in medicine—yes, really. Here’s why.

Published December 1, 2022

9 min read

A rare type of cancer called synovial sarcoma landed Ellie Lofgreen at the University of Utah Hospital this summer. A tumor the size of a small grape was removed by surgeons. They also removed a few inches from her knee joint and cut off a few inches of bone. They placed a metal implant into her leg and covered it with large flaps of muscle and skin from her upper thigh. The flap started turning purple a few hours later. This was a sign that the transplanted tissue was beginning to die.

Saving the graft was critical so the medical team proposed a treatment that surprised Lofgreen: leeches.

“I was absolutely floored,” says the 31-year-old Idaho resident. “My initial reaction was, Okay, anything but that.”

Aside from the yuck factor, the use of leeches in modern medicine often surprises patients given that these blood-sucking parasites were long dismissed as quackery. But their use in plastic and reconstructive surgery has picked up since 2004, when the U.S. Food and Drug Administration approved leeches as a medical device to relieve congested veins and restore blood flow in compromised grafts. Doctors attach tissue to another part in the body to maintain blood supply. These surgeries are usually successful. However, in the event that they don’t go according to plan, doctors will take the patient back into the operating room to reexamine the stitches and reattach blood vessels. This fix can fail, but it is not uncommon.

“Veins are so fragile,” says Jayant Agarwal, chief of plastic surgery at the University of Utah. For example, blood flow may still be restricted if a vein ends has been damaged in an accident. Sometimes, it can be difficult to find a vein in a severed hand. Leeches are useful because blood can pool in transplanted tissue if there is no connection.

They provide temporary life support, according to Jeffrey Janis, a plastic surgeon expert at Ohio State University Wexner Medical Center. This is until the body’s blood vessels grow into the transferred tissue. He says that without this help, the tissue could die.

Where medical leeches come from

Although there are more than 600 species of leeches, including some that don’t suck blood, the European Hirudo medicinalis and Mediterranean Hirudo verbana are most frequently used in medicine. They have three saw-like jaws, each bearing about 100 teeth that the animals use to puncture skin.

For decades, laboratories in several countries including United Kingdom, United States, France, Turkey, and Ukraine have been breeding these medical leeches. Carl Peters-Bond at Biopharm U.K., a company that supplies about half of the medical leeches used in hospitals globally, has been doing this for nearly 30 years. He says it takes between one and two years to raise a leech that is ready for medical use. The process involves feeding them at three weeks, eight to 10 weeks, and then at four to five months, after which they’re starved for up to two years. He says, “We only ship leeches without a full stomach.”

As soon as an emergency call arrives, Peters-Bond packs between a dozen and 60 leeches in a gel-filled jar and ships them to a hospital. Some hospitals have the ability to pre-order medical leeches and keep them in stock in a refrigerator in case a patient needs them. Peters-Bond points out that these leech therapy creatures are best before three months.

How leech therapy works

When a leech bites, it slowly sucks blood and injects compounds like hirudin and calin–present in its saliva–that keep the blood from clotting. Leech saliva also contains histamine-like substances that dilate blood vessels and improve blood flow. Physicians have also used anticoagulants like heparin to prevent blood clots from forming during reconstructive surgeries. Agarwal states that you still need to actively suck blood.

Depending on the size of the graft and the degree of congestion, leeching can continue for three to 10 days or more, until the tissue looks “less swollen, less purple, more normal,” Janis says. The process is overseen by medical staff, who replace every engorged leech with another starved one. Patients are kept in the hospital. Each critter is limited to one use and is then drowned in alcohol once it has finished its task.

Over the course of two weeks, Lofgreen had more than 100 leeches drain her dingy-looking tissue. Her family named each of these invertebrates with the help of nurses and crowdsourced suggestions via Facebook. Lofgreen loved Aleecha Keys and Clint Leechwood. She also liked Sir Leechwood and Queen Laleecha. Every four hours, a nurse would come in and place a new leech, which would suck blood anywhere between 15 to 120 minutes before falling off and landing on her bed. Doctors gave her blood transfusions during the therapy to replenish the blood lost.

Getting the leech to latch on was difficult at times. Keeping it there was more difficult. To contain the leech, nurses initially used a four-ounce plastic container, which they inverted and taped to Lofgreen’s skin. The critter would sometimes sneak out of the cup. Staff created a barrier by using gauze that had a hole for the leech to attach to. They hoped the gauze would keep the leech from wandering off to the skin around it. However, this wasn’t foolproof. Her mother and sister were the best watchers. They would watch out for rogue leeches throughout the day and alert the nurses immediately. Lofgreen did not feel any pain when the parasites bit into her transplanted tissue. However, it would prick sharply if they bit elsewhere. She describes it as “pins and needles”.

The part of her tissue which initially looked dark and necrotic became lighter and the skin became more normal. Lofgreen states that the leeches were successful. After she returned home, however, a small portion of her flap became infected and had the need to be removed. The infection was not due to leeching, but rather an open wound. She credits the slimy slithering animals with saving the majority the transplanted flap.

A study that looked at 277 cases of medical leech use reported a 78 percent success rate. Ernest Azzopardi (a plastic surgeon at University College London in England) said that it was a very attractive option to flap salvage. But a lack of robust randomized control trials, the gold standard for evaluating the effectiveness of an intervention, has meant less confidence in using leech therapy.

Another downside is that patients can develop skin infections in response to such treatments due to the Aeromonas bacteria that live in leech guts and are found in their saliva. Peters-Bond, a Leech breeder, doesn’t use antibiotics. He says that although antibiotics can clear the bacteria from the gut, they will return. “What we do is starve the leeches so there’s no presence of blood in the gut and the bacteria is at its minimum.” In hospitals, doctors typically prescribe patients antibiotics as a preventative measure, but evidence of some Aeromonas bacteria developing resistance to commonly-used drugs is emerging, making the therapy a challenging one to use.

Robotic leeches

For years, scientists have been searching for alternatives to leeching. Early attempts date back to the 19th century when leeches were in high demand in Europe and the invertebrates were becoming scarce and thus more expensive. In 1817, Jean-Baptiste Sarlandiere, a French anatomist and physiologist, for instance, developed a device called the bdellometer, which drained blood from patients.

Agarwal, for instance, has been working with colleagues at the University of Utah since 2013 to develop a mechanical leech that can deliver an anticoagulant but also mimic the leeches’ suction. The prototype is made up of a series of needles that puncture skin. A central needle supplies anticoagulant heparin to blood saturated tissue. The surrounding needles are connected to a pump to suction blood. This thumbpad-sized device would allow doctors control the volume and speed of blood aspiration, which is impossible when using real leeches. The team is currently working to improve the flow of anticoagulant into tissue where the device is attached.

Other scientists, too, have developed similar prototypes that hold promise. Some have tested their performance in animals. Azzopardi states that there is no mechanical replacement for the parasite that is ready to be used in humans. These blood-sucking parasites will continue to be an important part of modern medicine for the time being.

Read More