INTRODUCTION

Use of leeches in medicine dates from the Stone Age to the present and has stretched across the globe (Spear, 2016). In the past, leeches were believed to remove evil spirits or humors from the body, while present knowledge of the unique properties of Hirudo medicinalis allows for its application to various surgical situations, particularly in reconstructive surgery. Leech therapy does carry complications, however, which must be considered and addressed before deciding on and initiating therapy.

HISTORY OF LEECHES IN MODERN MEDICINE

The key to the leech's success was discovered in 1884 by British physiologist John Haycraft when he discovered the leech secretes hirudin, a potent anticoagulant (Spear, 2016). Released from the leech's salivary glands, the polypeptide hirudin binds with high affinity to the coagulation enzyme thrombin, blocking further formation of fibrin from fibrinogen and thus inhibiting the coagulation cascade. As such, prior to the discovery of heparin, hirudin was one of the few agents known and used to inhibit clotting and has been used as an anticoagulant during blood transfusions since the early 1900s (Derganc & Zdravic, 1960). In 1955, hirudin was first successfully isolated by Markwardt, reducing the importance of the animal in favor of its product (Spear, 2016). Further investigations through the 1990s resulted in the ability to genetically engineer this potent anticoagulant.

UTILITY OF LEECH THERAPY

The primary indication for use of leeches in the field of plastic and reconstructive surgery is to prevent venous congestion of flaps used for soft tissue coverage of defects (Beier, Horch, & Kneser, 2010). Leeches have been applied to reconstructive scenarios such as avulsion injuries (i.e., ear, lip, nose, and digit replantation), microvascular free-tissue transfer, and locoregional flap salvage (Herlin et al., 2017). A 2004 study found that 80% of plastic and reconstructive surgeons in the UK had used leech therapy in the past 5 years on compromised free-tissue transfer or replantation operations (Spear, 2016). During microvascular surgery, arterial anastomosis is often easier to accomplish than venous anastomosis, with congestion in the flap or replant resulting from restricted venous outflow. To prevent flap or replant loss, H. medicinalis can be used to remove blood that cannot otherwise exit (Spear, 2016). Flap congestion in the setting of poor venous drainage has been shown to decrease in early leech therapy application, with flap salvage rates varying between 65% and 80% depending on the study (Herlin et al., 2017; Welshhans & Hom, 2016). Leech therapy is of variable duration and generally corresponds to the time required to achieve neovascularization between the flap and receiving site (Herlin et al., 2017).

COMMON COMPLICATIONS

The main complication of leech therapy is excess hemorrhage, which can be treated with direct pressure and topical thrombin and, if necessary, transfusion (Spear, 2016). However, the most serious complication is infection, as the leech's digestive tract contains the gram-negative bacillus Aeromonas hydrophilia, which breaks down the ingested blood. Infection can arise 2 to 7 days after leech therapy and may present as an abscess or cellulitis, with progression to sepsis possible. Infection can be prevented by prophylactic antibiotics continuing for 2 weeks after therapy discontinuation, usually with third-generation cephalosporins, fluoroquinolones, or trimethoprim-sulfamethoxazole, though fluoroquinolone resistance has been reported (Herlin et al., 2017). Other complications of leech therapy, though rare, include pain, hypotension, and allergic reactions (Herlin et al., 2017; Spear, 2016). Contraindications to leech therapy include immunocompromised patients, those with bleeding disorders, preexisting arterial insufficiency, or patients with conditions that pose a high risk of blood loss or infection (Herlin et al., 2017).

LEECH ALTERNATIVES

Not every hospital has ready access to leeches but alternatives exist should a situation arise in which a leech would be useful. The general approach is to make an incision into the congested area and then apply heparin, either by subcutaneous injection or continuous infusion, to ensure adequate flow of blood (Derganc & Zdravic, 1960; Iglesias & Butron, 1999). Unfortunately, heparin is simply not as good an anticoagulant as hirudin, so blood clots must be removed regularly to maintain blood flow (Robinson, 1998).

PROS, CONS, AND THE FUTURE OF LEECH THERAPY

The benefits of utilizing leeches to alleviate venous congestion in reconstructive procedures include increased viability of the flap from increased venous outflow as well as increased likelihood of replantation success in soft-tissue avulsion injuries. However, leech therapy is not a substitute for definitive operative management in cases of extreme venous congestion or arterial flow compromise (Welshhans & Hom, 2016). In the case of minor venous congestion, leech therapy may provide benefit, which must be weighed against the possibility of hemorrhage and infection.

CONCLUSIONS

With appropriate indication, leech therapy remains valuable in contemporary reconstructive surgery as an adjuvant to promote successful flap microvasculature survival, and can even make the difference between limb loss and salvage.

REFERENCES