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 (Weinfeld et al. 1998) (see Figure 4). Another example of the use of leeches in venous congestion is shown in a case report on a man diagnosed with a small interhemispheric subdural hematoma. The patient’s oropharynx was observed to be filled with the tongue producing an acute airway emergency (Grossman et al. 1998). The decision to undergo leech therapy in this case was made after just eight hours, and in the initiation of the therapy one or two leeches were applied to the ventral surface of the protuberant tongue (Grossman et al. 1998). The leeches remained in the position until satiated at which time they were replaced. A total of sixteen leeches were used with two six-hour time frames (Grossman et al. 1998). Within twenty hours of the therapeutical procedure there was a dramatic improvement in the lingual swelling (Grossman et al. 1998). The patient was able to move his tongue and the tongue could be reduced manually within the oral cavity (see Figure 5). The patients nasotracheal intubation (tube which allows for continued airflow to the patient), was removed 30 hours after admission and 48 hours after that, the patient was discharged (Grossman et al. 1998).
Leech therapy has also been used to salvage a venous congested penile replantation. The following case report was done on a schizophrenic man who amputated the distal third of his penis with a kitchen knife. Two days following surgery the patient began to show signs of venous congestion and consent was granted to undergo leech therapy. One to two leeches were applied daily to the distal penis for time periods ranging from 20 to 45 minutes (Pantuck et al. 1996). At the end of five days signs of venous congestion were no longer apparent and leech therapy was discontinued (Pantuck et al. 1996). In a follow-up done after three months, the leech therapy was observed to be successful, showing a well-healed functional phallus (Pantuck et al. 1996) (see Figure 6).
Overall, the objective of leech therapy is to produce adequate venous outflow from the tissue by adjusting the number and frequency of the application of the leeches to best suit the clinical situation. The application of leeches is initiated by signs of venous insufficiency or congestion and is terminated when these signs no longer exist. Medicinal leech therapy has also resurged in plastic surgery where it is mainly reserved for cases in which surgical correction is not possible, or for the temporary alleviation of venous congestion while the patient awaits a proper surgical intervention (Varghese et al.1996). Medicinal leeches may also be used successfully in decongesting blood flow in replanted parts including ears and digits, as well as segments of the lip, penis, nose and scalp (Daane et al. 1997). Leeches have also been used in breast reduction procedures (Daane et al. 1997).
Unfortunately, there are some complications that can arise from using leeches in therapeutic medicine. The first and foremost of these possible complications is wound infection (Varghese et al. 1996). The most common infection is due to the bacterium, A. hydrophila, which is a part of the normal gut flora of leeches (Varghese et al.1996). A. hydrophila plays an important role in the ability of the leeches to digest blood, by supplying proteolytic enzymes to the leech (Daane et al. 1997). This bacterium, a gram negative rod, can cause infection in patients at ratios varying from 0% to 20% within twenty-four hours to ten days after leech use, resulting in complications from minor would infection to the possibility of extensive tissue loss or damage (Daane et al. 1997). Antibiotics effective in fighting wound infection are penicillans, cephalosporins, tetracyclines and aminoglycosides (Haycox et al.1995).
Although leeches are not natural virus carriers, they can transmit viruses, such as hepatitis B, to humans if infected (Daane et al. 1997). In order to eliminate the risk of the transmission of these viruses, leeches are only reused if a method of filleting is applied to drain the ingested blood for emergency reuse. In most situations, the leeches are disposed of by placing them in a container of alcohol and then discarding with infectious waste (Daane et al. 1997). Other complications that can arise due to medicinal leech therapy is the possibility of extensive blood loss, where blood transfusions may be necessary (Daane et al. 1997). Transfusions are often required because of anticoagulation and the continuous flow of blood from the leeches feeding site (Daane et al. 1997). Also, allergic reactions to leeches have been reported (from the chemical constituents in the leech saliva), but allergic reactions to the common medicinal leech, H. medicinalis, is extremely rare (Daane et al. 1997).
Proper precautions and care should be used in handling leeches to reduce the risks of infection in patients (See Table 3). The risk of infection may be decreased by first dipping the leeches in 0.02% chlorhexidine hydrochloride solution for ten to fifteen seconds before applying the leech to the wound (Haycox et al.1995). Also, the administration of antibiotics to the patient before leech application has been proven to reduce the risks of infection (Haycox et al. 1995).
Leeches are also the source of the most potent anticoagulant found in nature, hirudin, the gene for which has now been cloned, and leech saliva may suppress the spread of tumors (Lent et al. 1988). Another chemical found in leech saliva is calin, which prevents platelets from attaching to collagen and forming plugs (Godfrey 1997). A new development from the Southern Illinois University is the “mechanical leech”. This leech consists of a suction chamber with continuous heparin infusions, attached at a full-thickness punch biopsy site (Daane et al. 1997). The new “mechanical leech” has proved to be superior to the medicinal leech in restoring blood flow in congested replanted tissue in rats. Perhaps the “mechanical leech” will take over the 3500 year old role of the medicinal leech in reconstructive surgery, opening new doors in the field of medical technology and render the ancient medicinal practice of using real leeches obsolete.
Despite the risk of wound infection and complications that can arise from medicinal leech therapy, most patients accept the use of leeches when presented with a clear explanation of the benefits (Daane et al. 1997). The survival rate for major replanted parts or revascularizations using leeches is about 85%, and the success rate for tissue transfers is about 95% (Varghese et al. 1996). Leeches increase the success of these operations by removing excess blood, which prevents the tissues from dying while the capillaries regrow (Lent 1990). Therefore, the ancient practice of leech therapy is still considered to be a well-accepted medical technique used in replantation and reconstructive procedures.
Table 1: Anticoagulants and related inhibitors from leeches (Eldor et al. 1996).
Table 2: Inhibitors of platelet aggregation from leeches (Eldor et al. 1996).
Table 3: Guidelines for the administration of leeches (Daane et al. 1997).
Figure 1: A single leech bite, consisting of a set of three incisions, one from each jaw (approximately 1mm). This bite was made in parafilm on a 37|C surface, a method for assessing leech hunger. However, leeches make similar wounds in the skin of their prey, and both kinds of bites resemble the Mercedes-Benz logo (Lent 1990).
Figure 2: Ventral view of a dissected leech head shows the animal’s nervous system and feeding organs (Lent et al.1988).
Figure 3: Feeding cycle of the medicinal leech alternated between hunger and satiation. The hunger phase consists of two subphases, appetite and ingestion. During the appetitive phase the leech swims toward wave sources. Once it finds a warm blooded host, it will feed for half an hour, consuming up to nine times its weight in blood. Satiated leeches do not bite; they avoid warm surfaces and hide under rocks or in crevices (Lent et al. 1988)
Figure 4: Before: Lower extremities of a 2-day -old baby girl with severe venous congestion 3 hours after ligation of the right common iliac vein for an unrepairable avulsion injury that occurred during cardiac catheterization. The thigh, leg, and foot are dark purple and edematous.
After: Lower extremities 1 year after leech therapy. Mild coetaneous hyperpigmentation is present in some regions; otherwise, the limb is clinically normal.
(Weinfeld et al. 1997)
Figure 5: Before: Appearance of tongue immediately after admission to the intensive care unit.
After: Appearance of tongue 30 hours after initiation of leech therapy.
(Grossman et al.1998)
Figure 6: Before: A single leech attached at the coronal junction. The penis, draped to prevent leech migration, appears dusky, tense, and edematous.
After: A three-month follow-up reveals a well-healed phallus.
(Pantuck et al. 1996)