MD, PhD, FMedSci, FRSB, FRCP, FRCPEd

Many people who have arrived at a certain age have knee osteoarthritis and most of them suffer pain, lack of mobility etc. because of it. There are many effective treatments for this condition, of course, but some have serious side-effects, others are tedious to follow and therefore not popular, and none of the existing options totally cure the problem. In many cases, surgery is the best solution; a knee-endoprosthesis can restore everything almost back to normal. But surgery carries risks and will cause considerable pain and rehabilitation-effort. This is perhaps why we are still looking for a treatment that is both effective and risk-free. Personally, I doubt that such a therapy will ever be found, but that does, of course, not stop alternative medicine enthusiasts from claiming that this or that treatment is what the world has been waiting for. The newest kid on this block is leech therapy. Did I just write “newest”? Leeches are not new at all; they are a treatment from the dark ages of medicine – but are they about to experience a come-back?

A recent systematic review and meta-analysis evaluated the effectiveness of medical leech therapy for osteoarthritis of the knee. Five electronic databases were screened to identify randomized (RCTs) and non randomized controlled clinical trials (CCTs) comparing leech therapy to any type of control condition. The main outcome measures were pain, functional impairment, and joint stiffness. Three RCTs and 1 CCT with a total of 237 patients with osteoarthritis were included. Three trials had, according to the review-authors, a low risk of bias. They claimed to have found strong evidence for immediate and short-term pain reduction, immediate improvement in patients’ physical function, and both immediate and long-term improvement in their joint stiffness. Moderate evidence was found for leech therapy’s short-term effects on physical function and long-term effects on pain. Leech therapy was not associated with any serious adverse events. The authors reached the following conclusion: ” Given the low number of reported adverse events, leech therapy may be a useful approach in treating this condition. Further high-quality RCTs are required for the conclusive judgment of its effectiveness and safety.”

When, about 35 years ago, I worked as a young doctor in the homeopathic hospital in Munich, I was taught how to apply leeches to my patients. We got the animals from a specialised supplier, put them on the patient’s skin and waited until they had bitten a little hole and started sucking the patient’s blood. Once they were full they spontaneously fell off and were then disposed off. Many patients were too disgusted with the prospect of leech therapy to agree to this intervention. Those who did were very impressed with the procedure; it occurred to me then that this therapy must be associated with an enormous placebo-effect simply because it is exotic, impressive and a treatment that no patient will ever forget.

The bite of the leech is not normally painful because the leech has a local anaesthetic which it applies in order to suck blood without being noticed. The leech furthermore injects a powerful anticoagulant into its victim’s body which is necessary for preventing the blood from clotting. Through the injection of these pharmacologically active substances, leeches can clearly be therapeutic and they are thus not entirely unknown in conventional medicine; in plastic surgery, for instance, they are sometimes being used to generate optimal results for micro surgical wounds. Their anticoagulant has long been identified and is sometimes being used therapeutically. The use of leeches for the management of osteoarthritis, however, is not a conventional concept. So, how convincing are the above data? Should we agree with the authors’ conclusion that “leech therapy may be a useful approach in treating this condition“? I think not, and here is why:

1) The collective evidence for efficacy is far from convincing. The few studies which were summarised in this systematic review are mostly those of the research group that also authored the review. Critical thinkers would insist on an independent assessment of those trials. Moreover, none of the trials was patient-blind (which would not be all that difficult to do), and thus the enormous placebo-effect of applying a leech might be the cause of all or most of the observed effect.

2) The authors claim that the treatment is safe. On the basis of just 250 patients treated under highly controlled conditions, this claim has almost no evidential basis.

3) As already mentioned above, there are many treatments which are more effective for improving pain and function than leeches.

4) Leech therapy is time-consuming, relatively expensive and quite unpractical as a regular, long-term therapy.

5) In my experience, patients will run a mile to avoid having something as ‘disgusting’ as leeches sucking blood from their body.

6) The animals need to be destroyed after the treatment to avoid infections.

7) As multiple leeches applied regularly will suck a significant volume of blood, the treatment might lead to anaemia and would be contra-indicated in patients with low haemoglobin levels.

8) Like most other treatments for osteoarthritis, leech therapy would not be curative but might just alleviate the symptoms temporarily.

On balance therefore, I very much doubt that the leech will have a come-back in the realm of osteoarthritis therapy. In fact, I think that, in this particular context, leeches are just a chapter from the dark ages of medicine. Their re-introduction into osteoarthritis care seems like a significant step into the wrong direction.

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