What is monopolar electroexcision of endometriosis and how does it differ from electrocoagulation?

Patients frequently ask, "How does electrosurgical excision of endometriosis differ from electrocoagulation of endometriosis?". The short answer is that excision cuts out the diseased tissue and electrocoagulation tries to destroy the diseased tissue using heat. The long answer, however, provides valuable insight into the important differences in surgical treatment approaches for endometriosis.

Electrosurgery: a primer
In discussing electrosurgical methods, it is useful to start with the basics of electricity. Electrical current is the flow of electrons through a conductor. Although we most commonly think of a conductor as some type of metal wire, many other types of conductors exist, including human tissue.

Some materials are good electrical conductors. Others are not. When a material is a poor or inadequate conductor for the load, it will create resistance to the flow of electrons. This resistance produces heat. Properly-sized copper or aluminum house wiring stays cool because the current flowing through it is small enough to be carried with little resistance. Copper and aluminum are good conductors, but not all metals are. Some metal, such as the heating element on an electric range, is made to generate resistance (and therefore heat).

Stainless steel surgical instruments (including laparoscopic scissors) are good conductors, so the metal itself does not heat up. The electrical effect we make use of in surgery is based on tissue resistance to electron flow.

Tissue resistance to electron flow causes the tissue to heat up around the tip of an electrode. The size of the conductor or electrode tip touching the tissue is also important, since a smaller electrode will deliver the electrons to a smaller surface area of tissue, resulting in a higher current density. Broader electrodes carrying the same amount of current will deliver the electrons across a greater surface area, resulting in a lower current density. Low current densities can be used to coagulate tissue (destroy it slowly using heat). High current densities can be used to vaporize the tissue.

Electrocoagulation of endometriosis is performed by touching a metal electrode to the disease and destroying it where it lies. The drawback is that the surgeon has no way of knowing whether the disease is being completely destroyed. This approach may also risk injury to underlying vital structures. Electroexcision of endometriosis, on the other hand, separates endometriosis from vital structures using blunt dissection and short bursts of high density current which cut tissue quickly.

For electricity to flow through tissue, it must be produced by an electrosurgical generator and complete a circuit back to that generator. In bipolar coagulation, the current flows down a metal electrode, then crosses over through the tissue to an opposing identical metal electrode which carries the current back to the generator and thus completes the circuit. The close proximity of the active electrode and the return electrode means that the current flows only through the tissue between the jaws of the bipolar coagulator.

In unipolar (also known as monopolar) coagulation, the electricity flows down an active electrode into the body. A conducting pad attached to the patient's thigh serves as the return electrode. In this approach, electrons flow back to the electrical generator by traveling a longer route through the patient's tissue.

High density, monopolar electrical energy does not result in widespread heat injury to the tissue because, as soon as the electrons enter the tissue under the active electrode, they spread out and find an infinite number of possible pathways back to the return electrode. This spread of electrons through the tissue lowers the current density within the tissue and prevents heat damage. This dilution of current strength, combined with appropriate constant movement of the active electrode reduces the risk of monopolar current. In fact, this may make monopolar electrosurgery safer than bipolar electrosurgery, since most bipolar instruments are designed to coagulate tissue by grasping it for several seconds while coagulating. This allows the paddles of the electrodes to heat up since they receive heat conducted from the tissue being coagulated, and also results in more widespread conduction of tissue heat itself.

Of course, either form of electrosurgery is only as safe as the operating surgeon using it. The point, however, is that monopolar electrosurgery is safe.

This new application to laparoscopic excision of endometriosis is especially significant since it finally combines all the desirable elements of surgery. It uses a technique that has proven (through long term follow-up) effective in eradicating or reducing endometriosis, it uses inexpensive technology available to surgeons worldwide, and, at long last, it increases the speed of laparoscopic surgery.

Back to the subject of electrocoagulation. This technique has not even been described in the literature, so there is no way to apply it consistently in patients. None of the important articles on electrocoagulation describe all the information needed to reproduce the technique - the type of electrosurgical generator used, the power setting, the type of electrode, or the surgical technique.

Increasing laparoscopic surgical efficiency with electroexcision
While doing surgery at laparotomy, I was always pleased with the apparent ease and efficiency with which I could perform the routine gynecological procedures. While doing laparoscopy, although I was pleased with my ability to perform more and more procedures, one thing was always lacking: a sense of speed.

My patient population presented surgical challenges which were already difficult enough. Long surgical times posed an additional challenge that neither I nor my patients needed. I was pleased with the success of simple excision in treating endometriosis, but it was clearly slower and more difficult than laser vaporization or electrocoagulation.

I knew this sense of slowness couldn't last forever, but I didn't know exactly how it would end. The solution came from an unexpected source. The surgical scissors I had used for years (Richard Wolf, #8380.02) were designed to accept a monopolar electrical cord. I had been taught, however, that "monopolar current in the pelvis is dangerous", so I never connected the cord. Of course, I had always used monopolar current for cutting tissue at laparotomy, so I knew subconsciously that this was not true. However, a mystique had built up over the years due to a few cases of bowel burns which occurred during tubal ligations performed with monopolar current.

Finally, in April 1991, I attached the monopolar electrical cord to the scissors. The result was outstanding. Monopolar electrosurgery has reduced the operating time on typical difficult endometriosis cases by 50% to 70% [1]. Bipolar coagulation was thought to be safer than monopolar current, but as the discussion above indicates, this is not so. The opposite may actually be true. In any event, $500 monopolar scissors cut 5-10 times faster than a $150,000 KTP/YAG laser and 2 -5 times faster than a $50,000 CO2 laser.

Another advantage of mono-polar electrosurgery is that instrument changes are virtually eliminated. The scissors can be used to cut, coagulate, blunt dissect, sharp dissect, grasp and rearrange tissue, and drive needles. This increases the efficiency and speed of surgery.

Laparoscopic surgery has made great advances in the past 10 years. As more surgeons attempt increasingly difficult procedures, the time spent in surgery will soon become an issue. Electrosurgical techniques may be one of our best tools to address these issues of speed.


  1. Redwine, D. B. (1993). Laparoscopic excision of endometriosis with 3 mm scissors: Comparison of operating times between sharp excision and electroexcision. Journal of American Association of Gynecologic Laparoscopists, 1, 24-30.