How do hospitals store leeches?

October 12, 2025 •

4 min read

Medicinal leeches, approved by the FDA as a medical device in 2004, require extremely specific handling and storage protocols. This article reveals exactly how do hospitals store leeches, outlining the stringent clinical standards for their maintenance and care to ensure they are safe and effective for patient treatment.

Quick Summary

Hospitals strictly regulate the storage of medicinal leeches, maintaining them in specific, temperature-controlled pharmacy environments. Unused leeches are housed in special containers with treated, non-chlorinated water and are handled with stringent hygiene protocols for safe, one-time patient use.

Key Points

Climate Control: Store in a cool, dark, temperature-controlled environment, ideally between 5–10°C (40–50°F), to slow metabolism and ensure health.
Specific Water: Use only distilled or non-chlorinated water supplemented with a mineral salt solution like HirudoSalt™ to maintain osmotic balance.
Secure Containers: Keep leeches in escape-proof jars with tight lids and micro-perforated ventilation to prevent their escape.
One-Time Use Policy: Each medicinal leech is used on a single patient and never reused to prevent cross-contamination.
Strict Disposal: Used leeches are humanely euthanized in a 70% alcohol solution and disposed of as biohazardous waste according to hospital regulations.
Pharmacy Management: The hospital pharmacy is responsible for all aspects of leech management, from storage and maintenance to dispensing and disposal.

Why Are Leeches Used in Modern Hospitals?

Contrary to popular belief, leeches are not a relic of antiquated medicine. They play a vital role in modern reconstructive and microsurgery, particularly in managing venous congestion. In procedures involving reattached digits (such as fingers or toes) or skin flaps, blood may flow into the tissue via arteries but become trapped due to insufficient venous outflow. This pooling of blood can cause the tissue to swell and potentially die. The medicinal leech (Hirudo medicinalis), when applied to the congested area, acts as a living anticoagulant. The bioactive substances in its saliva, including hirudin, prevent blood clotting, allowing excess blood to be drawn from the congested tissue. The resulting prolonged bleeding from the bite site helps restore circulation and promote the growth of new blood vessels, a process known as angiogenesis. For this reason, maintaining the leeches' viability and health is a critical task for hospital pharmacies.

The Hospital Pharmacy's Role in Leech Management

The hospital pharmacy is the central point of responsibility for ordering, storing, maintaining, and dispensing medicinal leeches. This centralized approach ensures that all protocols for quality, sterility, and safety are rigorously followed. The pharmacy staff, often a pharmacist or trained technician, is responsible for:

Receipt and Inspection: Verifying the shipment from FDA-approved suppliers, checking for damage or signs of distress among the leeches.
Initial Housing: Transferring leeches from their shipping container to long-term storage, which may involve a switch from a gel matrix to a water solution.
Daily Maintenance: Routinely checking the leeches for health, removing any dead specimens, and inspecting the water quality.
Dispensing: Releasing leeches to the appropriate medical team just before use, often in sterile, single-patient containers.
Record Keeping: Maintaining accurate logs of inventory, maintenance schedules, and patient usage to trace each lot of leeches.

Ideal Storage Conditions for Medicinal Leeches

Maintaining the correct environment is crucial for keeping leeches healthy and active. The storage conditions are carefully controlled to mimic their natural habitat and suppress metabolism.

Environmental Controls

Temperature: Leeches are extremely heat-sensitive and are typically kept in a cool, dark place. Most hospital guidelines recommend refrigeration at a controlled temperature of 5–10°C (40–50°F). This temperature range slows their metabolism, reducing the need for frequent water changes.
Light: Direct sunlight and bright artificial lights are avoided. Leeches are nocturnal and prefer a dark environment, so containers are often covered or placed in a light-restricted space.

Water Requirements

Type: Only distilled, bottled, or non-chlorinated water is used for storage. Chlorine and other chemicals found in tap water are toxic to leeches. The addition of a specific mineral salt, such as HirudoSalt™, is recommended to maintain the correct osmotic balance.
Volume: A sufficient volume of water is required to prevent overcrowding. A general guideline is no more than 50 leeches per 2.5–10 liters of water, depending on the container and protocol.
Changes: The water should be changed regularly, every one to three days, or whenever it appears murky or cloudy, as this can indicate stress or the presence of dead leeches.

Containers and Handling Protocols

Specialized, escape-proof containers are a non-negotiable part of hospital storage. Leeches are incredibly elastic and can squeeze through very small openings.

Secure Container Features

Secure Lids: The container must have a tightly fitting lid. For ventilation, it should have very small, pin-sized perforations or a secure, fine-mesh cloth cover held by a rubber band.
Design: Many hospitals use purpose-built containers like the "Easy Clean Leech Container" or a wide-mouthed jar for easy access and cleaning. Separate containers are used for different lots of leeches to prevent cross-contamination.

Handling Procedures

Gloved Hands: Staff must wear sterile, gloved hands when handling leeches to prevent the transfer of oils, detergents, or other substances that can harm the leeches.
Minimizing Stress: Gentle handling is crucial. Sudden temperature changes or rough treatment can cause leeches to become stressed or regurgitate their gut contents, increasing infection risk if later applied to a patient.
Never Re-Use: Each leech is strictly for single-use application on one patient. Once used, it must be discarded immediately.

Comparison of Hospital Leech Storage vs. Improper Methods


Feature	Correct Hospital Storage	Incorrect / Unsafe Practices
Environment	Cool (5-10°C), dark, climate-controlled pharmacy.	Warm rooms, direct sunlight, unstable temperatures.
Water	Distilled or non-chlorinated water with osmotic salt solution (e.g., HirudoSalt™).	Chlorinated tap water, mineral water, or distilled water alone.
Container	Escape-proof, wide-mouthed jars with secure, micro-perforated lids or fine mesh covers.	Loose-fitting lids, containers with large holes, or no cover.
Handling	Sterile, gloved hands, gentle treatment, separate lots.	Bare hands, rough handling, mixing different leech lots.
Disposal	Humane euthanization in 70% alcohol; disposed of as biohazardous waste.	Returning used leeches to pharmacy stock or general trash.

Safe Disposal of Medicinal Leeches

Proper disposal is the final, critical step in the lifecycle of a medicinal leech. Once a leech has been used on a patient, it is considered biohazardous waste due to the ingested blood and potential pathogens.

Euthanasia and Disposal Protocol

Collection: Used leeches are collected immediately after they detach from the patient and placed into a separate, labeled container.
Euthanasia: Staff submerge the leech in a solution of 70% alcohol for a period (often 5–15 minutes) to ensure its demise.
Hazardous Waste: The container with the euthanized leech is then disposed of in the hospital's biohazardous waste stream, which often includes incineration to meet regulatory guidelines. Unused leeches that are no longer needed are also euthanized in the same manner.

Conclusion

From the moment they arrive at the hospital pharmacy to their final disposal, medicinal leeches are subject to strict, controlled protocols. The careful management of storage conditions, including a cool, dark environment and specially prepared water, is vital for maintaining their therapeutic viability. Equally important are the rigorous handling and single-use application procedures, which mitigate infection risks and ensure patient safety. Ultimately, these stringent regulations are what make the age-old practice of hirudotherapy a legitimate and effective tool in modern medicine, especially in the delicate field of reconstructive microsurgery.

Frequently Asked Questions

Medicinal leeches are used in modern microsurgery, particularly for reattached body parts and skin grafts, to relieve venous congestion. Their saliva contains anticoagulants that prevent blood from clotting, helping to drain excess blood and promote circulation in the compromised tissue until new blood vessels can form.

Leeches are typically stored within the hospital's pharmacy, in a secure, climate-controlled refrigerator or cool, dark room. This placement allows for controlled handling and maintenance by trained personnel, separate from other medications and medical equipment.

Hospitals use distilled, non-chlorinated water with a special osmotic salt mixture, often called HirudoSalt™, to create the ideal aquatic environment for the leeches. Tap water, with its chemical additives like chlorine, is harmful and strictly avoided.

Leeches are typically transferred from the pharmacy's storage container into a smaller, separate, sealed container for single-patient transport. This ensures sterility and prevents escape. Application often involves guiding the leech into a syringe casing before placing it on the patient.

No, medicinal leeches are for single, one-time use on a single patient only. After feeding, a leech must be euthanized and disposed of as biohazardous waste to prevent cross-contamination and other risks.

While generally safe, risks include a small chance of infection from bacteria in the leech's gut (managed with prophylactic antibiotics), excessive bleeding, and the need for a blood transfusion in some cases. Careful monitoring is essential.

Dead leeches must be promptly removed to prevent contamination of the water, which can affect the health of the other leeches. If several leeches die, the water change frequency may be increased to daily until the remaining leeches stabilize.