Yes, the NHS Really Uses Leeches: Here Is Why

Yes, the NHS Really Uses Leeches and No, It Isn’t Medieval Medicine

They may look like something from a historical medical drama, but medicinal leeches still have a small and important role in modern reconstructive surgery.

In specialist NHS services, they can be used to relieve severe venous congestion and help salvage compromised tissue following procedures such as flap reconstruction or the reattachment of a finger, toe or ear (Hull University Teaching Hospitals NHS Trust, 2023; Oxford University Hospitals NHS Foundation Trust, 2024).

Wait… Did You Say Leeches?

Yes. Actual leeches.

Before you imagine someone arriving from a pond with a jam jar, there is an important distinction: medicinal leeches are specially bred and supplied for clinical use. They are applied only following a medical decision and according to local policy.

However, they should not be described as sterile. Medicinal leeches naturally carry Aeromonas bacteria within their digestive system, which is why infection prevention and prescribed antibiotic prophylaxis are important parts of treatment (Hull University Teaching Hospitals NHS Trust, 2023).

These unlikely little assistants can sometimes help save tissue when its venous drainage is failing.

🧬 The Science Bit: Why Do Leeches Work?

During reconstructive microsurgery, tissue may be transferred from one part of the body to another as a flap, or a severed body part may be surgically reattached.

For that tissue to survive, it needs:

• Adequate arterial inflow to deliver oxygenated blood.

• Adequate venous outflow to carry deoxygenated blood away.

Sometimes the arterial supply works, but venous drainage does not. Blood enters the tissue but cannot leave effectively. This is called venous congestion.

The affected tissue may become:

• Dusky, blue or purple.
• Swollen or tense.
• Cool.
• Rapidly refilling when capillary refill is assessed.
• Darkly bleeding when clinically tested.

Venous congestion is a surgical emergency because continued poor drainage can lead to microvascular thrombosis, impaired oxygen delivery and tissue loss.

Where possible, the surgical cause must be identified and corrected. Leech therapy may be considered when venous drainage cannot be restored immediately, further surgery is not possible or additional temporary drainage is needed (Oxford University Hospitals NHS Foundation Trust, 2024).

🪱 Enter the Medicinal Leech

Medicinal leeches, including Hirudo medicinalis and Hirudo verbana, attach to the congested tissue and remove a small quantity of blood.

Their saliva also contains biologically active substances, including:

• Hirudin and other anticoagulant compounds, which reduce clot formation.
• Calin, which contributes to continued bleeding from the bite after the leech detaches.
• Vasoactive substances, which can support local blood flow.

You may read that leech saliva contains a local anaesthetic. Some NHS patient information describes an anaesthetic-like effect, and treatment is often reported as relatively painless. However, the precise contribution of anaesthetic compounds is less firmly established than the anticoagulant effect, so it is better not to promise that the patient will feel nothing.

The leech provides immediate, temporary blood removal, while anticoagulation allows the bite site to continue oozing after it detaches. This creates an alternative route for congested blood to leave the tissue.

Treatment may be repeated while new venous connections develop or until the surgical team is satisfied that the tissue can maintain adequate circulation independently (Hull University Teaching Hospitals NHS Trust, 2023).

🧪 When Might Leeches Be Used in the UK?

Medicinal leech therapy is most commonly associated with specialist services such as:

• Plastic and reconstructive surgery.
• Hand and upper-limb surgery.
• Microsurgical free-flap reconstruction.
• Maxillofacial surgery.
• Ear, nose and throat surgery.
• Major trauma and burns reconstruction.
• Replantation of fingers, toes, ears or other tissue.

Leeches are primarily used for venously congested flaps or replanted tissue. It is more accurate to say this than to suggest they are routinely applied to ordinary skin grafts.

The number of leeches, frequency of application and duration of treatment depend on the tissue involved, its clinical appearance, the response to treatment and the specialist team’s protocol.

A leech commonly remains attached for approximately 15–60 minutes before becoming full and detaching by itself. Bleeding from the bite may continue for several hours afterwards, which is an intended part of the treatment but requires close observation (Hull University Teaching Hospitals NHS Trust, 2023).

😳 But… Aren’t They Gross?

Honestly? Some patients and students may find them difficult to look at initially.

They move, attach to the skin and become noticeably larger as they feed. However, watching a congested, dusky area become less tense and better perfused can quickly change how you see them.

They are not being used because modern medicine has run out of ideas. They are used because their combination of controlled blood removal and prolonged local anticoagulation can be difficult to reproduce in such delicate tissue.

Published evidence suggests that leech therapy can contribute to the salvage of selected congested flaps and replanted tissues. However, much of the evidence comes from case series and observational studies rather than large randomised trials, so success cannot be guaranteed in every case (Mousavian et al., 2022).

🧤 Student Nurse POV: What Might You See?

A student nurse should not independently initiate, apply, remove or dispose of medicinal leeches unless this forms part of an approved local procedure and they are directly supervised by an appropriately trained registered professional.

Depending on your placement, you may observe or assist with:

• Assessing the colour, warmth, swelling and capillary refill of the affected tissue.
• Following the prescribed flap-observation schedule.
• Watching for changes in venous congestion.
• Recording when each leech was applied and when it detached.
• Monitoring bleeding and the condition of each bite site.
• Checking dressings and estimating blood loss where required.
• Observing the patient for pain, distress, infection or deterioration.
• Reviewing blood results, particularly haemoglobin, as directed by the clinical team.
• Confirming that prescribed antibiotics have been administered.
• Maintaining containment so the leech does not migrate away from the treatment site.
• Documenting care clearly and escalating concerns promptly.

Never pull off, squeeze, salt, flick or otherwise disturb an attached leech. Follow the specialist team’s instructions and the organisation’s leech-therapy policy.

Bleepbook Tip: They may not wear scrubs, but while they are attached to the patient, treat them like specialist equipment: observe them closely, document properly and do not improvise.

⚠️ Risks and Safety

Leech therapy requires close monitoring because it is not risk-free.

Infection

Medicinal leeches naturally carry Aeromonas species in their gut. These bacteria help the leech digest blood but can cause wound infection or, more rarely, serious systemic infection in the patient.

Patients are therefore commonly prescribed antibiotic prophylaxis according to microbiology advice and local antimicrobial policy. Antibiotic choice should never be guessed, because resistance patterns can vary (Sproll et al., 2022).

Bleeding and anaemia

Continued bleeding after detachment is part of how the treatment works. However, repeated applications can result in clinically significant blood loss.

The team may monitor:

• The amount of bleeding.
• Haemoglobin and the wider full blood count.
• Haemodynamic observations.
• Symptoms of anaemia.
• Whether blood transfusion is required.

Tissue failure

Leech therapy does not guarantee that a flap or reattached body part will survive. Persistent or worsening congestion must be escalated immediately because urgent surgical assessment or re-exploration may be required.

Migration

A leech may move away from the intended treatment area if it is not appropriately contained. The patient, treatment site and surrounding bedding therefore require careful observation.

Psychological distress

Some patients may feel frightened, disgusted or anxious about the treatment. Clear explanations, consent, privacy and reassurance remain important.

Cross-infection

Each leech is used for one patient only and must never be reused. Once detached, it is disposed of humanely as contaminated clinical waste in accordance with local organisational policy (Hull University Teaching Hospitals NHS Trust, 2023).

🚨 What Should You Escalate?

Tell the registered nurse or surgical team immediately if you notice:

• Increasing duskiness, swelling or coolness.
• A sudden change in capillary refill.
• Reduced or absent expected bleeding from the bite site.
• Uncontrolled or excessive bleeding.
• A falling haemoglobin or signs of haemodynamic instability.
• Increasing pain.
• Spreading redness, discharge, fever or other signs of infection.
• A missing or uncontained leech.

• Any sudden change in the patient or the appearance of the flap.

Flap observations are time-critical. If something looks different, do not wait for the next scheduled observation before escalating.

💬 The Takeaway

Medicinal leech therapy is not a return to indiscriminate historical bloodletting. It is a controlled, specialist treatment used in selected cases of venous congestion following reconstructive surgery.

The leech removes congested blood, its saliva helps maintain local bleeding, and the treatment may buy valuable time for venous drainage to recover or new vascular connections to develop.

So, the next time someone jokes about “medieval medicine”, you can tell them:

“Actually, medicinal leeches still have a place in reconstructive surgery, they just don’t wear scrubs.”

References

Hull University Teaching Hospitals NHS Trust (2023) Leech therapy. Available at: https://www.hey.nhs.uk/patient-leaflet/leech-therapy/ 

Mousavian, A., Sabzevari, S., Parsazad, S., Moosavian, H. and Leili, E.K. (2022) ‘Leech therapy protects free flaps against venous congestion, thrombus formation, and ischemia/reperfusion injury: benefits, complications, and contradictions’, Archives of Bone and Joint Surgery, 10(4), pp. 252–260. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC9034796/.

Oxford University Hospitals NHS Foundation Trust (2024) Leech therapy. Available at: https://www.ouh.nhs.uk/media/syif1xee/78372therapy.pdf

Sproll, C., Lommen, J., Cleven, A.H.G., Möllmann, H.L., Kübler, N.R. and Rana, M. (2022) ‘Lethal Aeromonas veronii sepsis in the course of medicinal leech therapy’, Antibiotics, 11(9), 1180. Available at: https://doi.org/10.3390/antibiotics11091180.