New device muscles in on medicinal leeches

Scientists at the University of Wisconsin-Madison have gone some way to make medicinal leeches redundant with the creation of a mechanical leech.

Scientists from the University of Wisconsin-Madison have created a device that effectively performs the same function as the medicinal leech – promoting the flow of blood to compromised tissue – without the unpleasantness of having a blood-sucking parasite attached to your body.

‘In the case of the leech in medicine, we think we can improve on nature,’ said Nadine Connor, a scientist who is part of a University of Wisconsin-Madison and William S. Middleton Memorial Veterans Administration Hospital team that has designed and tested the mechanical leech. ‘We believe a mechanical device can be more effective.’

Historically, the leech’s beneficial bite has been applied to treat a variety of ailments. In the context of modern medicine, the leech has re-emerged as an important and effective therapy and is used exclusively to treat venous congestion.

‘Venous congestion is a post-surgical complication that can occur after reconstructive surgery,’ Connor said. ‘What happens is the arteries pump blood into the reconstructed tissue, but the associated veins do not let the blood flow out, usually because the veins have become clotted. The excess blood in the tissue, if severe enough, can deprive the tissue of oxygen and other nutrients and can cause it to die.’

‘Leeching’ can be effective as it helps to re-establish blood circulation in the affected part of the body, Connor said. Most often, venous congestion arises where tissue is moved from one place to another.

In cases of venous congestion where re-establishing the flow of blood is essential, leeches have great therapeutic value because they promote blood flow through the tissue. Even after a leech is full of blood and detaches from the body, the anticoagulants it secretes into the tissue allow the wound to ooze blood for hours afterward. The oozing promoted by the leech’s natural anticoagulants also allows blood to continue flowing through the tissue.

Meanwhile, during leech therapy, which can last for up to 10 days, new veins grow into the reconstructed region from surrounding healthy tissue and help re-establish adequate blood drainage. But leeches have their drawbacks in that they are not sterile and can cause bacterial infections.

The mechanical leech developed at UW-Madison has distinct advantages over its flesh-and-blood counterpart, according to Michael Conforti, a scientist at the William S. Middleton Memorial Veterans Administration Hospital and another of the mechanical leech’s inventors.

Conforti said the device can better deliver and disperse the anticoagulant heparin to affected tissue, and the device’s porous tip, implanted just beneath the skin, rotates to further inhibit coagulation.

Moreover, unlike the real leech, the mechanical leech is insatiable and can remove greater quantities of blood, thereby increasing the flow of blood to the tissue being treated.

‘There is a big difference between what a real leech can do and what our mechanical leech can do,’ said Conforti. ‘The real leech can penetrate only so deep. Our device can act at a deeper level under the skin, tapping into larger blood vessels and treat a larger area of tissue.’

‘But perhaps the mechanical device’s biggest advantage is that it is not a leech,’ said Connor: ‘People don’t want this disgusting organism hanging on their body. This added psychological stress for both patient and family members compounds an already difficult situation.’