Historical Review
Therapeutic Use of Leeches: From the “Annelids” of Medicine
Robert Adam, BSc. (0T5)
Peter Zakrzewski, BSc. (0T4)
Abstract
Long before the stethoscope and blood pressure cuff, it was
not uncommon to find doctors making house calls with a
box of leeches in their medical kits. Today, it is common to
find surgical departments storing sterile leeches as well as
several leech chemical extracts. The uses of the leech in
medicine have evolved over three millennia, from instruments used for harmful bloodletting to invaluable surgical
tools.
Until the 19th century, and the development of competent diagnostic skills, many medical practices were unscientific, unproven,
traditional cultural procedures, largely based on superstitious ideas
and religious philosophy. Bloodletting was perhaps one of the
most infamous and consistent of these medical myths. Many early
cultures believed that evil, disease-causing spirits could be vanquished by releasing blood from the afflicted individual.
Bloodletting was therefore practiced by many ancient cultures, in
one form or another, and archaeologists have even discovered evidence of bloodletting at Stone Age camp sites.1 The use of leeches in medical practice is believed to have originated in the Far
East,2 as means of controlling blood loss during bloodletting.
However, the earliest conclusive evidence of leeching is in the
form of an illustration discovered in an Egyptian tomb from 1500
B.C.2 The first documented therapeutic use of leeches is from the
poem Alexipharmaca by Nicander of Colophon (200-130 B.C.).1
Two of the most enthusiastic proponents of bloodletting were
Hypocrates – the father of medicine, and Galen – the personal
court physician to Marcus Aurelius. These giants of medicine
believed that the four crucial elements earth, air, water, and fire
were balanced within the human body as the four humors: blood,
phlegm, and black and yellow bile. It was thought that disease was
due to an imbalance in the four humors and treatment involved
restoring their balance through bloodletting.
Leeches served a valuable purpose, as they allowed a surgeon to
remove predictable and controlled quantities of blood. The most
common species of leech used for this purpose was, and still is,
Hirudo medicinalis. This hermaphroditic annelid is about ten centimeters long when fully extended and can ingest about 5-10 millilitres of blood in one feeding. Ancient Roman bloodletters often
severed the leech’s tail in order to induce continuous blood loss
and reduce the number of leeches needed in one bloodletting session.2 This fresh-water species was favoured for its long and
bloody bite, the product of three jaws and hundreds of teeth that
cut the skin using a sawing motion.
Leeches permitted bloodletters to control the amount of blood
withdrawn, whereas previously, patients often died as a result of
the procedure itself. In fact, George Washington died in this manner after heavy blood loss sustained in a bloodletting treatment for
laryngitis.2 (One could say that he wasn’t impeached, but
imleeched!) Leeching became so popular in the Middle Ages that
the practice was even taken up by barbers. People went to barbers or surgeons to be bled on a regular basis. In fact, red and
white, the traditional colours of the barber’s pole, are said to represent the blood and bandages that were staple tools of the barber shop in the days when “a little off the top” was a crucial statement for the patrons to make. The etymology of the modern term
leech can even be traced back to find its roots in the old English
word “laece,” meaning physician.1
The popularity of leeching peaked in France during the 1820s and
1830s.3 Francois Broussais, a heralded physician and bloodletter of
the day, proposed that all disease was due to inflammation caused
by excessive accumulation of blood in a particular part of the
body. Broussais felt that releasing this internal pressure through
leeching would cure the patient of most ailments. The theory of
irritation was another popular medical approach during this time
that also called for bloodletting as a universal cure. This theory
proposed that disease could be relieved by treatments that caused
opposing symptoms to those of the disease. Leeching was therefore prescribed for diseases such as laryngitis, nephritis, mental illness and obesity. During this era of leeching obsession, the animal
was in such high demand that it was even considered an endangered species for a short time. France had to import over forty
million German leeches annually. Over six million of these leeches were used in Parisian hospitals alone.3
The practice of bloodletting with leeches was commonplace in
North America as well. During the American Yellow fever epidemic of 1793, leeching was attributed with saving thousands of
people from the fatal infection.2 It must be kept in mind that
physicians at this time had extremely limited knowledge of physiology and microbiology, and inconsistent information with respect
volume 79, number 1, December 2001
65
to the pathology of disease and hence diagnosis. Medical practices
were often based on intuition, impression, and doctrine, rather
than proven scientific methods. Even as late as 1912, William
Osler advocated leeching in his treatise Practice of Medicine, stating, “To bleed at the very onset in robust healthy individuals in
whom disease sets in with great intensity and high fever, I believe
is a good practice”.1
Modern medicine may look at the long history of bloodletting with
leeches in disbelief; however, the practice did not subside until the
beginning of the 20th century. It was with the development of
more stringent diagnostic and treatment techniques, based on consistent and documented experimental method, that bloodletting
was finally realized to be detrimental to health. It must be realized that prior to these advancements, the pressure on physicians
to “do something” for suffering patients was a very real one. For
an oft-dumbfounded doctor, with relatively few tools at their disposal, bloodletting at least provided some hope for the ill. It was
a socially acceptable practice supported by years of superstitious
and religious beliefs made safer by the introduction of the leech.
At the very least, bloodletting allayed the patient’s apprehension
and provided some hope for recovery.
After almost a century of exile, leeches have crept back to medical respectability, thanks to their unmatched ability to drain excess
blood from injured tissue. In prestigious hospitals the world over,
leeches are biting into patients undergoing various plastic and
reconstructive surgeries. Although technological advances in these
surgical specialties have allowed thousands of patients to benefit
from the successful reattachment of body parts, some of these
operations might have failed had leeches not been reintroduced
into the operating room. Appendages reattached with the aid of
leeches include fingers, hands, toes, legs, ears, noses, and scalps.
Leeches have also been used in breast reduction.4
In 1994, a woman’s scalp was ripped off when her hair was pulled
into moving machinery. Doctors performing micro-surgery at the
University of Southern California reattached the scalp, but one area
of tissue swelled with congested blood. With no other safe alternative available, the surgeons applied leeches, one at a time for
eight days, to suck up the stagnant blood and allow proper healing. While the scalp healed, new capillaries formed in the scalp
wound, and a healthy circulation eventually formed.5
Another clinical example of leech use involved a 28-year-old man
whose right ear had been almost completely severed with a knife.
The surgery to attach the ear was successful; however, approximately one hour after revascularization, the ear showed signs of
venous congestion. Rather than risk injury to the delicate arterial
anastomoses during exploration of the venous anastomoses, the
decision was made to treat the venous congestion with Hirudo
medicinalis and anticoagulation. On attachment of the first leech,
the ear quickly lost the congested appearance and became pink.
Leeches were applied to the ear one to three times per day for five
days as needed to relieve venous congestion, and the ear eventually regained proper blood flow without the need of further medical treatment.6
66
University of Toronto Medical Journal
These clinical examples illustrate the use of leeches in modern medicine, but what exactly makes them so useful medically? The main
therapeutic benefit of the leech is not simply the large amount of
blood removed by the leeches during tissue attachment, but rather
the released salivary secretions.
The leech produces a number of secretions in the saliva, including
an anesthetic, an anticoagulant (hirudin), a local vasodilator (histamine), and the enzyme hyaluronidase. These secretions result in the
“leeched” area bleeding as much as 150 mL of blood for up to 48
hours. On average, leech bites bleed for six hours and can be
stopped when required by treatment with pro-coagulent therapy.
The ability of the leech bite wound to bleed for this extended period of time appears to be related to the combination of the pharmacologically active secretions, not just the anticoagulant alone.
Efforts to simulate prolonged bleeding with conventional anticoagulants, such as heparin, into small stab wounds in the skin have been
unsuccessful.7
During surgery to reattach a piece of tissue, firm-walled arteries are
fairly easy to spot and stitch together, but flimsy veins tend to crumple, disappearing into the damaged tissue. Thus, re-establishment of
venous circulation from the grafted tissue is often inadequate, and
while blood can flow into the tissue, it has no outlet and backs up
like water in a leaf-choked gutter. Unless the buildup is cleared
quickly, the sluggish blood will begin to coagulate, spawning clots
that can plug the arteries nourishing the tissue. If this happens, the
tissue will become ischemic and eventually die.8
The backup of venous blood is referred to as venous insufficiency
and is a major problem when blood pools in damaged tissue. The
clinical sign of venous insufficiency is the flesh turning blue and
puffy. Surgeons accustomed to using leeches recognize this sign as
the time to summon their invertebrate assistants. The leech then acts
as a substitute vein, drinking off the excess blood and preventing
clotting until new veins can sprout and restore normal circulation.8
Advantages in using leeches are their low cost (approximately $7.50$9 CAD each), their long shelf life (they can survive for months
soaking in a slightly saline solution), and the painlessness of their bites
due to the natural anaesthetic. Surprisingly, patients do not react
adversely to the suggestion of leech use. Two physicians with more
than 20 years of leeching between them reported that they have
never had a patient refuse leech treatment due to squeamishness.8
Leeches have some peculiar disadvantages that require extra attention by doctors and nurses. Excess bleeding is the biggest post-treatment concern, and transfusions have occasionally been needed to
prevent anemia. Commensal bacteria living in the intestine of the
leech sometimes enter the wound and cause infection, but this can
be prevented with prophylactic antibiotics. Perhaps the most fearsome problem with the leech is its innate desire to find dark, snug
places to digest its meal. Without the watchful eye of the doctor or
nurse, an adventurous leech can burrow its way into the wound, or
even more disturbing, the patient’s mouth or other orifices.8
The comeback of leech-use in modern surgeries can be credited to
two Slovenian surgeons, M. Derganc and F. Zdravic, who published
a paper in the British Journal of Plastic Surgery in 1960 describing
leech-assisted tissue flap surgery (where a flap of skin is freed or
rotated from an adjacent body area to cover a defect or injury).
These surgeons credit their own use of leeches to a Parisian surgeon,
Philippe-Frédéric, who reported in 1836 that he had used leeches to
restore circulation following reconstruction of a nose.4
After such an amazing resurgence in the world of medicine, will
leeches take on more medical roles, perhaps returning to the popularity they enjoyed in the mid 1800s? Not likely. Apart from their
bloodsucking role, they are useless against most medical conditions.
Furthermore, scientists are currently developing a mechanical leech
that could do the job of the real leech without the risk of infection
nor the risk of “losing” the leech on, or in, the patient!8
You Want It All.
We have it right here.
Is the rat race, high cost of living, hours of travel time and
costs, resulting in poor quality of life for you and your family?
Are you tired of harsh winters and difficult commutes? Then
come to Ontario’s “banana belt” in the heart of Southwester
Ontario, surrounded by some of Canada’s greatest natural
resources, provincial parks, lakes and waterways and one of the
richest agricultural areas in the Country.
Enjoy a better quality of life and higher income, while you raise
your family in one of our safe and affordable communities in
city, town,
village and rural settings. Recreational and educational opportunities abound here and we are central to larger urban centres
such as Toronto, London and Detroit.
Family Practice Physicians
✓ Group or solo practice available
✓ On-site physician office complex being developed
✓ ER Shifts available with APP
✓ Strong Partnerships with academic centres
✓ Attractive incentives, relocation and start-up programs
To Have It All, Call
CHATHAM-KENT
Health Alliance
Alliance de Chatham-Kent pour santé
The largest community
hospital in Ontario
is looking for
physicians in...
Figure 1. A leech being applied to restore proper blood
flow in a skin flap attached to a hand.
Family & Emergency
Medicine
Psychiatry
Cardiology
References
1. Upshaw J and O’Leary JP. (2000). The medicinal leech: past and present. Am
Surgeon. 66(3): 313-314.
2. Marderasian AD. (1999). Medicinal leeching past and present. ThromboSite Newsletter.
1(3): 1-12.
3. Graf J. (2000). The symbiosis of Aeromonas and Hirudo medicinalis, the medicinal leech. ASM News. 66: 147-153
4. Sawyer RT. (2000). Biopharm Leeches Online. Retrieved October 10, 2001, from
the World Wide Web: http://www.biopharm-leeches.com
5. Weinstock M and Bregman M. (1998). Gross Medicine. Retrieved October 10,
2001, from the World Wide Web: http://teacher.scholastic.com/researchtools/articlearchives/ humanbody/grossmedicine.htm
6. Funk GF, Bauman NM, Rinehart RJ, and Mankarious LA. (1996). Microvascualar
replantation of a traumatically amputated ear. Arch of Otolaryngol Head Neck Surg.
122(2): 184-186.
7. Yurevich S. (2001). Medical use of leeches. Retrieved October 10, 2001, from the
World Wide Web: http://www.geocities.com/leechlady5/page2.html
8. Leslie M. (1999). Stanford Surgical helpers are out for blood. Retrieved October
10, 2001, from the World Wide Web: http://www-med.stanford.edu/center/communications/publications/stanmed/previous_issues.1999spring/leeches.html
Dermatology
Gastroenterology
Neurology
Geriatrics
Infectious Diseases
Endocrinology
Oncology
Radiology
Lou Emery, V.P.
Tel: (519) 628-4100
E-mail: [email protected]
www.physicianswanted.com
At William Osler Health Centre, we are passionate about the
way we do business. We are looking for physicians that can
help us shape the future of healthcare in a corporation poised
for considerable growth and development.
William Osler Health Centre has more than 640 physicians
and serves a population in excess of 700,000. This population
base gives William Osler Health Centre the critical mass to
provide regional specialized services in such areas as
Paediatrics, Neonatology, MRI, Dialysis and Orthopaedics.
Together the Etobicoke Hospital, Brampton Memorial
Hospital and Georgetown Hospital Campuses provide care to
Canada’s fastest growing communities.
Fast Facts:
• Planning for new hospital in Brampton and expansion
of the Etobicoke and Georgetown campuses
• 160,000 emergency visits annually
• 185,000 outpatient visits annually
• home to over 7,000 births annually
• has an annual operating budget of over $220 million
• 3 acute care campuses linked electronically
• over 400 physicians electronically linked from
home and/or office
• access to health and dental benefits
• large and growing ambulatory care services
• has a catchment (service) area of 1200 square kilometres
For more information about medical opportunities at
William Osler Health Centre, please contact:
Dr. Tom Dickson, Chief of Staff
905-796-4461 or [email protected]
It’s All About People Caring About People!
volume 79, number 1, December 2001
67