The humble leech's medical magic

By Melissa Jackson
BBC News Online health staff

Leeches have a long medical pedigree (picture courtesy of Biopharm Leeches)

The latest endorsement for using blood-sucking leeches for medical purposes has come from the US government.

In a world where medical advances are dominated by developments in drugs and surgery it seems that in certain fields these humble creatures cannot be beaten.

They are highly prized as a tool for healing skin grafts or restoring circulation, especially in reconstructive surgery.

Now the US Food and Drug Administration has approved an application from French firm Ricarimpex SAS to market leeches for medicinal purposes.

These hungry little Draculas have been used in medicine for centuries and were first employed in Egypt about 2,500 years ago.

Later, they were applied to treat all kinds of ailments from headaches to gout.

Through bloodletting, it was thought that leeches would drain "impure blood" from the body, thereby curing illness.

Much the same as maggots and a small list of other treatments, leeches still have their place in modern medicine Ken Dunn, consultant burns and plastic surgeon

Eventually, scientific research showed that leeches were unlikely to stop a headache, but are useful in surgery.

They are often used today in plastic and reconstructive surgery, because a natural anticoagulant they secrete fights blood clots and restores proper blood flow to inflamed parts of the body.

Thousands of patients owe the successful reattachment of body parts to miraculous technological advances in plastic and reconstructive surgery.

But some of these operations might have failed if leeches had not been reintroduced into the operating room.

The appendages reattached include fingers, hands, toes, legs, ears, noses and nipples following breast reconstructive surgery.

Buying time

During operations, micro surgeons usually have little trouble attaching the two ends of the arteries, because arteries are thick-walled and relatively easy to suture.

Veins, however, are thin-walled and especially difficult to suture, particularly if the tissue is badly damaged.

All too often the surgeon can get blood to flow in the reattached arteries but not veins.

With the venous circulation severely compromised, the blood going to the reattached finger becomes congested, or stagnant; the reattached portion turns blue and lifeless and is at serious risk of being lost.

It is in these cases that leeches are summoned.

The secret is in the saliva (picture courtesy of Biopharm Leeches)

Ken Dunn, consultant burns and plastic surgeon at the South Manchester Burns and Plastic Surgery Service said: "We use leeches to establish a flow of blood through tissue where there is congestion of blood, usually because the flow of venous blood out is not adequate, while the arterial flow of blood into the tissue is good or excellent.

"The treatment simply buys time for the venous drainage to open up and improve, usually 3-5 days. If this is not done the tissue will die from that congestion of blood.

"Leeches are extremely effective and better than simply putting a hole in the tissue to make it bleed because the leech lines the bite they make with a good anticoagulant that is very long lasting.

"On average the tissue bleeds about 10 times the volume of blood that the leech actually removes to feed on, making it a very efficient and effective treatment.

"Treatment with a single leech will last hours and allow blood flow in the tissue during that time."

Natural anaesthetic

The key to success is the exploitation of a unique property of the leech bite, namely, the creation of a puncture wound that bleeds literally for hours.

The leech's saliva contains substances that anaesthetise the wound area, dilate the blood vessels to increase blood flow and prevent the blood from clotting.

Mr Dunn said: "Leeches are a treatment associated with medieval times and appear a tad dated.

"However, much the same as maggots and a small list of other treatments, leeches still have their place in modern medicine."

They do have their drawbacks, one of which is the patients' squeamishness about having three-inch slimy parasites attached to their wounds.

They can sometimes slip off patients and reattach themselves to other parts of the body not in need of therapy.

However if you are ever in that unfortunate position of needing leech therapy, it may be a case of lie back and think of something more attractive if it means saving a limb.