Leeches are bloodsucking worms with segmented bodies. They belong to the same large classification of worms as earthworms and certain oceanic worms.
Leeches can primarily be found in freshwater lakes, ponds, or rivers. They range in size from 0.2 in (5 mm) to nearly 18 in (45 cm) and have two characteristic suckers located at either end of their bodies. Leeches consume the blood of a wide variety of animal hosts, ranging from fish to humans. To feed, a leech first attaches itself to the host using the suckers. One of these suckers surrounds the leech's mouth, which contains three sets of jaws that bite into the host's flesh, making a Y-shaped incision. As the leech begins to feed, its saliva releases chemicals that dilate blood vessels, thin the blood, and deaden the pain of the bite. Because of the saliva's effects, a person bitten by a leech may not even be aware of it until afterwards, when he or she sees the incision and the trickle of blood that is difficult to stop.
For centuries, leeches were a common tool of doctors, who believed that many diseases were the result of "imbalances" in the body that could be stabilized by releasing blood. For example, leeches were sometimes attached to veins in the temples to treat headaches. Advances in medical knowledge led doctors to abandon bloodletting and the use of leeches in the mid-nineteenth century. In recent years, however, doctors have found a new purpose for leeches—helping to restore blood circulation to grafted or severely injured tissue.
There are many occasions in medicine, mostly in surgery and trauma care, when blood accumulates and causes trouble. Leeches can be used to reduce the swelling of any tissue that is holding too much blood. This problem is most likely to occur in two situations:
- Trauma. Large blood clots resulting from trauma can threaten tissue survival by their size and pressure. Blood clots can also obstruct the patient's airway.
- Surgical procedures involving reattachment of severed body parts or tissue reconstruction following burns. In these situations it is difficult for the surgeon to make a route for blood to leave the affected part and return to the circulation. The hardest part of reattaching severed extremities like fingers, toes and ears is to reconnect the tiny veins. If the veins are not reconnected, blood will accumulate in the injured area. A similar situation occurs when plastic surgeons move large flaps of skin to replace skin lost to burns, trauma or radical surgery. The skin flaps often drain blood poorly, get congested, and begin to die. Leeches have come to the rescue in both situations.
It is important to use only leeches that have been raised in the laboratory under sterile conditions in order to protect patients from infection. Therapeutic leeches belong to one of two species—Hirudo michaelseni or Hirudo medicinalis.
One or more leeches are applied to the swollen area, depending on the size of the graft or injury, and left on for several hours. The benefits of the treatment lie not in the amount of blood that the leeches ingest, but in the anti-bloodclotting (anticoagulant) enzymes in the saliva that allow blood to flow from the bite for up to six hours after the animal is detached, effectively draining away blood that could otherwise accumulate and cause tissue death. Leech saliva has been described as a better anticoagulant than many currently available to treat strokes and heart attacks. Active investigation of the chemicals in leech saliva is currently under way, and one anticoagulant drug, hirudin, is derived from the tissues of Hirudo medicinalis.
The leeches are removed by pulling them off or by loosening their grip with cocaine, heat, or acid. The used leeches are then killed by placing them in an alcohol solution and disposed of as a biohazard. Proper care of the patient's sore is important, as is monitoring the rate at which it bleeds after the leech is removed. Any clots that form at the wound site during treatment should be removed to ensure effective blood flow.
Infection is a constant possibility until the sore heals. It is also necessary to monitor the amount of blood that the leeches have removed from the patient, since a
drop in red blood cell counts could occur in rare cases of prolonged bleeding.
Adams, J. F., and L. F. Lassen. "Leech Therapy for Venous Congestion Following Myocutaneous Pectoralis Flap Reconstruction." ORL - Head & Neck Nursing 13, no. 1 (Winter 1995): 12-14.
Daane, S., et al. "Clinical Use of Leeches in Reconstructive Surgery." American Journal of Orthopedics 26, no. 8 (Aug. 1997): 528-532.
de Chalain, T., et al. "Successful Use of Leeches in the Treatment of Purpura Fulminans." Annals of Plastic Surgery 35, no. 3 (Sept. 1995): 300-306.
de Chalain, T. M. "Exploring the Use of the Medicinal Leech: A Clinical Risk-Benefit Analysis." Source Journal of Reconstructive Microsurgery 12, no. 3 (Apr. 1996): 165-172.
de Chalain, T., and G. Jones. "Replantation of the Avulsed Pinna: 100 Percent Survival with a Single Arterial Anastomosis and Substitution of Leeches for a Venous Anastomosis." Plastic & Reconstructive Surgery 95, no. 7 (June 1995): 1275-1279.
Godfrey, K. "Uses of Leeches and Leech Saliva in Clinical Practice." Nursing Times 93, no. 9 (26 Feb. 1997): 62-63.
Goessl, C., et al. "Leech Therapy for Massive Scrotal Mematoma Following Percutaneous Transluminal Angioplasty." Journal of Urology 158, no. 2 (Aug. 1997): 545.
Haycox, C. L., et al. "Indications and Complications of Medicinal Leech Therapy." Journal of the American Academy of Dermatology 33, no. 6 (Dec. 1995): 1053-1055.
Iafolla, A. K. "Medicinal Leeches in the Postoperative Care of Bladder Exstrophy." Journal of Perinatology 15, no. 2 (Mar./Apr. 1995): 135-138.
Lee, N. J., and N. S. Peckitt. "Treatment of a Sublingual Hematoma with Medicinal Leeches: Report of Case."
Pantuck, A. J., et al. "Penile Replantation Using the Leech Hirudo medicinalis." Urology 48, no. 6 (Dec. 1996): 953-956.
Piascik, P. "Medicinal Leeches: Ancient Therapy Is a Source of Biotech Drugs." Journal of the American Pharmaceutical Association NS37, no. 3 (1997): 285-286.
Smeets, I. M., and I. Engelberts. "The Use of Leeches in a Case of Post-Operative Life-Threatening Macroglossia." Journal of Laryngology & Otology 109, no. 5 (May 1995): 442-444.
Van Wingerden, J. J., and J. H. Oosthuizen. "Use of the Local Leech Hirudo michaelseni in Reconstructive Plastic and Hand Surgery." South African Journal of Surgery 35, no. 1 (Feb. 1997): 29-31.
Wallis, R. B. "Hirudins: From Leeches to Man." Seminars in Thrombosis & Hemostasis 22, no. 2 (1996): 185-196.
J. Ricker Polsdorfer, MD