Journal Citation

Rothenberger J, Petersen W, Schaller HE, Held M. Determining the appropriate number and duration of leech therapy in congested tissues using tissue spectrophotometry and laser Doppler flowmetry. Wound Repair Regen. 2016;24:1023-1029.

Published Abstract

A universal protocol determining the number of leeches and their application time does not exist. The aim of this study, therefore, is to quantify perfusion dynamics in venous congested tissues after leech application to get more detailed information about changes due to leech-induced skin microcirculation and to evaluate the usability of the Oxygen to See (O2C) device in terms of determining the appropriate number of leeches and the duration of therapy. Twelve patients with the need for leech therapy participated in the study. Perfusion dynamics of the congested tissue was assessed using the O2C device, which determines blood flow (BF), the relative amount of hemoglobin (rHB), and the oxygen saturation (SO2). Measurements were carried out before leech application and on various intervals like 10 minutes, one hour, and three hours after leech application. The leech application effectuated after 10 minutes a nonsignificant perfusion improvement, which further increased after one hour with a significant reduction of the relative amount of hemoglobin and a significant increase of blood flow and oxygen saturation (BF5 156.7%; rHB5 225.5%; SO25 153.7%). After three hours, the values returned to the levels before leech administration. In two cases, in which further administration of leeches within the measurement period was necessary, no substantial perfusion changes were obtained. The results of this study forms a more precise pattern of microcirculatory changes of leech therapy in congested tissues. According to our measurements a venous drainage improvement can be expected in congested tissue one hour after leech administration. The O2C seems to be a useful method to determine the appropriate number and duration of leech therapy.


In reconstructive and transplant surgery, arterial circulation can be established or repaired surgically; but surgical repair of venous circulation (to carry the blood back to the heart) is rarely feasible. Usually, the patient and the doctor must wait for nature to reconnect (anastomose) the venous drainage. When venous drainage is not re-established quickly enough, the blood pools in the affected area and this vascular congestion can prevent fresh oxygenated blood from reaching the area. In order to decompress or remove the pooled venous blood, leech therapy is often used. The leeches suck the blood and secrete vasodilatory and anticoagulant proteins which allow the blood to continue draining, even after the leech finishes feeding and drops off.

One common dilemma for surgeons is how many leeches to place, and how often should the leeches be placed, in order to provide adequate drainage. To date, the answers to these questions has been guided by clinical observation. But doctors like objective measures – tests – that can guide if not dictate their treatment decisions. This is the origin of this study: the search for objective measures of circulatory integrity which can inform the surgeon about the number, frequency, and duration of leech phlebotomy to relieve post-surgical congestion.

In this project, the researchers investigated the use of the Oxygen to See (O2C) device, which can determine blood flow, flow velocity, relative amount of hemoglobin, and oxygen saturation, using a combination of white light and laser light  (830 nm and 30 mW). Twelve patients who needed leech therapy for compromised flaps had their perfusion dynamics assessed with the O2C device before and after leeching. It should be noted that the decision to continue or halt leeching for these patients was reached based on clinical data. The spectrophotometric and doppler flowmetry data that was collected was not used to decide how many total leeches or leech treatments.


A total of 12 patients were enrolled in this study. Their surgical interventions differed; their outcomes differed. Four subjects underwent sural flaps. All four flaps survived, but one experienced a major necrosis. One of these subjects (not the one suffering major necrosis) was assessed clinically to need additional leech treatments and was so treated. Four subjects had successful anterior lateral thigh flaps. One of these subjects required additional leech treatments, based on clinical evaluation. Two subjects had random pattern flaps, one of which survived with only minor necrosis, the other was lost. One subject underwent a dorsal metacarpal artery flap, which survived with only minor necrosis. One subject had a digit replantation which, unfortunately, was not successful.

For the two subjects who required more than a single application of leeches, tissue spectrophotometry and laser Doppler flowmetry was not continued throughout the entire 3 hour study period. Within 10 minutes for one patient and within 1 hour for the second patient, blood flow and relative amount of hemoglobin failed to change, although hemoglobin oxygenation may have arguably increased slightly. Nevertheless, on the basis of clinical evaluation of the patients (sill very poor circulation and oxygenation), measurements were halted and further leech treatments were administered.

For the remaining 10 subjects who were treated with only one application of leeches, their average blood flow and hemoglobin oxygenation increased within 1 hour and relative amount of hemoglobin decreased within an hour, consistent with decompression of the vascular congestion (stagnation of blood) and increased flow of fresh arterial blood into the area. After 3 hours, these values, on average, returned to baseline.


This study clearly adds objective measurements that corroborate our understanding of the benefits of leech therapy for post-operative venous congestion: Stagnated venous blood is removed by the leeches, resulting in decreased local pressure and consequently increased in-flow of fresh, oxygenated arterial blood. These findings are not unique; they have been demonstrated multiple times by other researchers, as reviewed by the current authors. What is unique is their use of this particular piece of technology (the O2C device) which measures both tissue photometrics and doppler flow.

But what of their stated goal: using this or a similar technology to help guide decisions concerning the need for additional leeching? This works us a little closer to that point, by pointing out the fact that we can monitor these meaningful physiological changes, but we are still a few way away from being able to predict or recommend optimal therapy based on such objective measures. The reasons we are still so far away are related to the shortcomings of this study.

One obvious shortcoming was the technology itself. While the O2C appears to be a fine piece of equipment, it was not a simple matter to adjust the probes such that they could reliably and consistently perform optimally, given the anatomy of these post-surgical sites and the reality of live leeches hanging from the tissue. Another shortcoming was the study design itself. Remember that this was not a test of the hypothesis that O2C could help decide whether or not additional leeching was necessary. That promise may have driven the researchers forwards, but this study was simply about the feasibility of gathering meaningful physiological data. This the researchers proved was possible. In order to determine whether or not this data can predict outcomes or drive  clinical decisions, a study should be performed in which the decisions to leech or not to leech are actually made on the basis of this data, and outcomes are then evaluated to determine whether or not the data and decision parameters were successful.

But such a study would be a big jump from where we are right now. So here is something that the authors could do right now: they could re-examine the data they have (or collect additional data) to evaluate not the average results for each study subject, but the specific results, with an eye towards cut-off points. The fact that patients who required only one leech treatment, on average, had increased blood flow or decreased relative hemoglobin does not tell us whether or not these markers are predictive, if in fact many of the subjects had blood flow that did not increase, or relative hemoglobin that did not fall. In the world of useful decision points, “average” is not as meaningful as sensitivity and specificity: HOW MANY of the subjects actually had blood flow that increased? What percent of subjects actually had relative hemoglobin measurements that decreased? By how much? This is the next step that has to take place before we can determine whether or not this physiologic data could be useful in directing the course of leech therapy. It looks like the data may be at hand – in the hands of the authors. If so, I hope to hear more from them about this study or future studies.

Still, my review of this report leaves me feeling that our technology is not yet advanced enough to assist us any more than what we already have at our fingertips: leeches to help with the problem of venous congestion, and a trained human brain to observe the patient and determine whether or not our patient needs that leech’s help.


– Reviewed by: Dr. Ronald Sherman