The leech has three sharp jaws that make a wound shaped like a Mercedes-Benz symbol, into which it injects a local anesthetic elaborated by perioral glands. The constant flow of blood is ensured by an anticoagulant that prevents clotting during and for several hours after the bloodsucking activity.

These remarkable characteristics have been recognized since ancient times, and, although there existed no scientific justification, the leech was widely used as a medical treatment.

The earliest documented use of leeches is found on an Egyptian tomb wall painting from the 18th Dynasty (1567-1308 BC). Leeching is described in detail in the early Sanskrit system of medicine of ancient India. The Greeks and Romans also used leech therapy several centuries BC.

John Hunter, in his book, A Treatise of Blood, Inflammation and Gunshot Wounds, discusses the use of leeches and cautions against their use in patients with gunshot wounds. The use of leeches was widespread in Europe during the 17th century and peaked during the first part of the 19th century, largely due to the influence of Broussais, Napoleon's military surgeon. During that time, French hospitals were using enormous numbers of leeches. Based on French import records, over a billion leeches were imported into France during the 19th century. Their use was so extensive that in 1910 the medicinal leech was thought to be extinct in Britain.

In 1884, Haycroft of Wales isolated hirudin, the anticoagulant elaborated by the leeches. It was not until 1955, however, that hirudin was chemically analyzed and found to be a small peptide consisting of 65 amino acids with specific antithrombin activity.

Renewed interest in leeches has developed over the past several years, particularly in microsurgery. Foucher et al. have reported the use of leeches to successfully treat digit replants4,5 where no venous outflow vessels were available. They applied a leech twice a day for 5 days and salvaged 6 of 10 such cases.

The successful use of leeches in the treatment of venous congestion in skin flaps6,7 has increased the investigation and use of the leech. These animals may well provide the only solution to such a vexing problem as venous congestion in an ear replant, where there is no suitable axial venous outflow.8

Leech Anatomy and Physiology

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