Medical leeches, particularly Hirudo medicinalis, bridge ancient practices and modern science. Once widely used, they have seen a resurgence in contemporary healthcare. Their distinct biological properties offer targeted therapeutic benefits.
Biological Mechanisms of Action
Medical leeches exert their therapeutic effects through bioactive compounds found in their saliva. Upon biting, the leech introduces substances that modify the host’s physiological responses. One such compound is hirudin, a potent polypeptide that acts as a direct thrombin inhibitor, preventing blood clotting and ensuring continuous blood flow at the bite site.
The saliva also contains hyaluronidase, an enzyme that degrades hyaluronic acid. This action increases tissue permeability, allowing other bioactive molecules to spread more effectively into surrounding tissues. Other compounds like calin, destabilase, saratin, bdellins, and eglins also contribute. Calin acts as an anticoagulant, while destabilase helps break down fibrin clots.
These molecules reduce blood viscosity, enhance localized blood flow, and provide anti-inflammatory and anti-platelet effects. Some also possess mild analgesic properties, numbing the bite area. This combined action improves circulation and tissue health.
Contemporary Medical Applications
Modern medicine uses leeches for venous congestion and improved blood flow. Their most common application is in microsurgery, particularly after reattaching severed body parts such as fingers, toes, or ears.
Following such procedures, arteries are reconnected, but smaller, more fragile veins may struggle to adequately drain blood, leading to pooling and swelling. Leeches draw out excess blood, decompressing engorged tissues and restoring proper circulation. This action helps prevent tissue death and increases the success rate of reattachment procedures. For digits, success can rise from below 20% to over 50% with leeches.
Beyond microsurgery, leeches find use in managing hematomas, which are collections of clotted blood. By drawing out stagnant blood and introducing anticoagulant compounds, leeches reduce swelling and promote healing. They are also employed in dermatological or orthopedic conditions for localized blood removal or anti-inflammatory effects, such as severe bruising.
The Therapy Procedure and Patient Management
The application of medical leeches in a clinical setting is a carefully managed process. Leeches, typically Hirudo medicinalis, are specifically bred for medical use in sterile environments. Before application, the target area on the patient’s skin is thoroughly cleaned. A medical professional guides one or more leeches to the precise location requiring treatment.
Patients generally experience minimal discomfort during attachment, as leech saliva contains a natural anesthetic. Once attached, the leech feeds until full, typically for 15 to 60 minutes, then naturally detaches. The number of leeches used and the frequency of application are determined by the medical team based on the patient’s specific needs.
Following detachment, the small Y-shaped bite wounds may continue to ooze blood for several hours due to the anticoagulants in the leech’s saliva. Medical staff closely monitor the treated area for signs of continued bleeding and tissue color, and patient blood counts are regularly checked. To prevent infection, patients receive prophylactic antibiotics for the duration of the therapy. Used leeches are humanely disposed of after a single use.