The Use Of Leeches In Modern Therapeutic

Medicine Essay, Research Paper

The Use of Leeches in Modern Therapeutic Medicine

The use of leeches as a method of bloodletting reached a peak during the eighteenth and early nineteenth centuries. At that time, leeches were used by apothecaries and surgeons, in addition to lancets, scarifiers and bleeding cups, in an attempt to restore health by removing vitiated blood (Eldor et al. 1996). The first medical practitioner to use leeches for therapeutic purposes is presumed to be Nicander of Colophan and the use of leeched was mentioned in ancient Chinese, Sanskrit, Persian and Arabic literature as well as in the Old Testament (Eldor et al. 1996). In the past, leeches were applied to congested or inflamed areas of the body in conditions of engorged hemorrhoids, swollen testicles, laryngitis, prolapsed rectum and inflamed vulva (Eldor et al. 1996). The demise of leech therapy was a long overdue triumph of science over superstition. However, this practice is making a major comeback. Medicinal leeches, Hirudinea medicinalis, are now used by plastic surgeons to remove blood from postoperative occlusions in order to increase the success of tissue transplants, reduction mammoplasty, and the surgical reattachment of amputated extremities and digits by reducing the frequency of necrosis (Lent 1990). Leeches are also used in the treatment of post-phlebetic syndrome, which is a complication that occurs as a result of venous valve destruction (Eldor et al. 1996). Therefore, leeches are beneficial in overcoming many of the problems commonly associated with reconstructive surgery and venous congestion.

The medicinal leech, H. medicinalis, belongs to the group of Arhinchobdellida in the Class Hirudinea (Huguet et al. 1999). Leeches are segmented hermaphroditic, freshwater worms of the phylum Annelida and are equipped with two suckers used for clinging and crawling (Eldor et al. 1996). The smaller, anterior sucker houses the mouth which then leads to the buccal cavity which contains three jaws each bearing a row of denticles. Rhythmic contractions of the jaw muscles move the jaws back and forth which results in the cutting of the host’s skin in a distinctive Mercedes Benz mark (see Figure 1). Saliva is secreted from ducts which contains hirudin (which acts as the principle anticoagulant) and inhibitors of platelet aggregation (See Tables 1 and 2 for a list of additional anticoagulants and inhibitors).

As blood flows into the buccal cavity, it is pumped into the crop by rhythmic contractions of the pharynx (see Figure 2). Leeches ingest massive blood meals of 900% of their body weight, and their satiation often lasts for a year (Lent 1988) (see Figure 3). The lowered sensitivity to pain from a leech bite has been related to two complementary activities of leech saliva that reduce kinin-like activity in the host’s blood. Initially, the plasma kallikrein is inhibited, which is determined by the inhibition of kininogenase activity and secondly, the kininase activity is inhibited (Eldor et al. 1996).

After transplanting or reattaching tissues, venous return sometimes fails which reduces the arterial supply of blood and eventually results in tissue necrosis. The leech removes excess blood from occluded tissues to prevent necrosis, which provides the necessary time for the capillaries to grow across the sutures (Lent 1990). The leech secretes the anticoagulants into the wound and aspirated blood in order to maintain a continuous flow of blood (Eldor et al. 1996). Once satiated, the leech drops off and the bite continues to bleed for several hours after detaching. Once the leech drops from the bitten site, some minor itching and scarring of the bite wound may occur. The bites are then cleaned with an antiseptic and covered with dry gauze and an elastic bandage to avoid excessive bleeding (Eldor et al. 1996). In nature, satiated leeched are much less active and tend to hide for periods of twelve to eighteen months (Eldor et al. 1996). During this time, they digest the blood with the assistance of Aeromonas hydrophila, which is a symbiotic bacterium in the intestine of H. medicinalis (Lent et al. 1988).

Leech therapy is used in a variety of cases to relieve venous congestion. Leeches are said to have the ability to reestablish venous outflow, maintaining nutritive capillary perfusion of the compromised tissue until neovascularity is established (Pantuck et al, 1996). A case report done on the management of acute venous congestion on an infant’s lower limb describes the effectiveness of leech therapy. The infant’s venous congestion was due to the ligation of the right common vein, and although alternatives to leech therapy are available after close examination and careful considerations of the patient’s condition the use of leeches rather than a surgical operation was decided upon (Weinfeld et al 1998). To begin the procedure two leeches were applied, one the anterior tibial region and the other to the plantar surface of the foot. As the leech therapy proceeded two leeches were used concurrently at time intervals of 60 to 120 minutes (Weinfeld et al. 1998). Following the detachment of a leech, sterile heparin-soaked gauze spongers were applied to the bleeding puncture sites to promote continued drainage. The leech therapy in this case proved to be successful and at a one year follow-up the child had normal motor and sensory function in the right lower limb (Weinf