Endometrial Ablation Technique

Endometrial sampling before ablation can help rule out current malignancy. However, malignancy can be masked after an ablation. Accordingly, one should consider alternatives to ablation for patients who are at very high risk for endometrial cancer. There is no known increased risk for endometrial malignancy after endometrial ablation.

Postoperatively, patients who have had endometrial ablation are able to go home on the day of the procedure. Postoperative pain is typically controlled with ibuprofen. The recommended follow-up is 2 weeks after the procedure.

Concomitant microinsert placement

Essure devices are small microinserts containing a stainless steel inner coil with polyester fibers and a superelastic nitinol outer anchoring coil. This device is inserted hysteroscopically into the fallopian tubes for contraception.

No data suggest that these procedures cannot be done at the same time as an endometrial ablation. There has been concern that uterine synechiae would interfere with the ability to perform and interpret the hysterosalpingogram that is normally performed 3 months postoperatively, but data have shown that uterine synechiae did not interfere with the ability to document proper location of the Essure device or the ability to grade the degree of tubal occlusion. ^[44]

Because the Essure microinserts are made of nickel-titanium, there is the potential for energy conduction when bipolar energy ablation is used. When endometrial ablation is being done concomitantly with hysteroscopic tubal occlusion, performing the ablation before placing microinsert placement should prevent such complications. ^[44]

Essure has also been shown to be safe for use in conjunction with thermal balloon ablation for accomplishing endometrial ablation and permanent sterilization. ^[45] The ThermaChoice is approved by the US Food and Drug Administration (FDA) for this indication, but the NovaSure has not been and thus would be an off-label choice. ^[46]

Concomitant use of Adiana catheter

The Adiana catheter (Hologic, Bedford, MA) is a catheter inserted hysteroscopically into the fallopian tubes for contraception. The catheter delivers a low level of radiofrequency (RF) energy and then releases a silicon matrix that allows scar tissue to form, blocking the fallopian tubes. There is no metal in the device to interfere with energy conduction during endometrial ablation. At present, only limited data are available time regarding the safety of using the Adiana catheter concomitantly with endometrial ablation.

Mirena versus endometrial ablation

The levonorgestrel-releasing intrauterine device (IUD) marketed as Mirena (Bayer HealthCare Pharmaceuticals, Wayne, NJ) is effective for reducing heavy menstrual bleeding. Multiple studies have compared the effects of this IUD with those of endometrial ablation, with varying results. A meta-analysis found Mirena and endometrial ablation to be comparable in terms of menstrual blood loss and overall quality of life. ^{[33, 47]}

Resectoscopic endometrial ablation (REA) procedures include rollerball (roller barrel) desiccation, laser vaporization, and wire-loop resection. All of these procedures are performed through the resectoscope under direct visualization with laser energy or with monopolar or bipolar RF energy sources. In general, REA procedures are less costly than global endometrial ablation (GEA) procedures.

For standard monopolar electrosurgical techniques, distention media typically consist of low-viscosity, electrolyte-free solutions (eg, 1.5% glycine, 3% sorbitol, 5% mannitol, or combined sorbitol-mannitol). The potential for systemic intravasation of these solutions and subsequent adverse sequelae necessitates use of a strict fluid measurement and management system, preferably automated, to monitor differences between fluid instilled and fluid returned. To further reduce intravasation risk, the lowest effective intracavitary pressure should be used.

Newer bipolar devices are also available; however, the small gauge of the device (typically < 5 mm) results in increased operating times. Electrolyte-free distention media are not required, allowing the operator to use normal saline instead. Consequently, there is not the same risk of fluid intravasation, and this advantage may outweigh the risks of increased operating time for an experienced operator.

Rollerball (roller barrel) desiccation

The distention medium is introduced, the power is set to 50-150 W on the generator, and monopolar energy is used to desiccate the endometrium. The rollerball is initially placed at the fundus, then moved to the anterior and lateral walls, and finally moved to the posterior wall. The goal is to destroy the visible endometrium to a depth of 1-2 mm; this prevents regeneration because the basal and spiral arterioles do not survive the exposure. The procedure is approximately 30 minutes in duration.

Laser vaporization

A neodymium:yttrium-aluminum-garnet (Nd:YAG) laser is placed through the instrument channel of the hysteroscope. The laser fibers touch and then photocoagulate the endometrial tissue. Because of the high cost of the equipment and the considerable training required, this procedure is not commonly used.

Wire-loop resection

A wire loop is used with the operative hysteroscope to manually resect the endometrium to a depth of 5-6 mm. The loop is connected to either a monopolar or a bipolar electric current.

Each GEA technique requires thorough knowledge of the equipment, the procedure, and intraoperative response of the uterus and endometrium (see the Table below). The newer tools for GEA require less operator time and training to achieve excellent results than the earlier devices did.

Table. Global Endometrial Ablation Techniques (Open Table in a new window)

Almost all GEA devices are designed with fail-safe mechanisms to detect procedural abnormalities (eg, uterine cavity defects, fluid loss, and pressure loss). Some are also designed to automatically detect procedure completion, as in the case of the NovaSure, which measures tissue impedance to determine depth of ablation in an attempt to ensure proper treatment.

Thermal balloon ablation

In its first iteration, ThermaChoice consisted of a latex balloon. This was replaced with a silicone balloon in ThermaChoice II. The third generation of the device, ThermaChoice III, uses a stronger and more flexible Silastic balloon, thereby improving coverage throughout the cavity and, potentially, over small submucosal myomas smaller than 2 cm.

Thermal balloon ablation is performed via a cannula. Advance the balloon-tipped probe into the cavity and inflate it with 5% dextrose in water (D5W) to a pressure of 160-180 mm Hg, up to a total of 30 mL of fluid (see the image below).

Activate the device (this requires a minimum pressure of 150 mm Hg). It automatically passes through a 2-minute warm-up phase, then an 8-minute ablation phase, and finally a 2-minute cooldown phase. During the ablation phase, the fluid is maintained at 87°C. Tissue is destroyed to a depth of 3.3-5 mm.

The system automatically shuts down under the following conditions:

• Rapid decrease in pressure

• Pressure >210 mm Hg

• Pressure < 45 mm Hg, temperature >95°C

• Temperature < 75°C for > 15 seconds

The procedure is performed blindly, and total procedure time is approximately 30 minutes.

It is important to keep in mind that the ThermaChoice requires a pressure of 160-180 mm Hg for proper application of the balloon to the endometrial cavity. During the initial filling of the balloon, the operator may notice a rapid increase in uterine pressure as a result of a uterine contraction, which is typically self-limited. After completion of the initial filling of the balloon, the uterus may relax, resulting in a slight loss of pressure. This can be addressed by continued slow filling if the pressure has stabilized to a less-than-optimal level.

Occasionally, a uterine contraction may be encountered during the ablation phase, resulting in intracavitary pressures exceeding the predetermined device limit and possible automatic cessation of the procedure. This can be remedied by releasing a small amount of fluid from the balloon intraoperatively to maintain the appropriate pressure.

Alternatively, uterine relaxation may be encountered during the ablation phase. However, additional fluid injection is not recommended, because the introduction of cool fluid would compromise endometrial cavitary temperature. It is reasonable to continue the procedure; the device will continue ablation as long as the pressure remains above 45 mm Hg (though it should ideally be at least 100 mm Hg to ensure minimally adequate pressure within the cavity).

Cryoablation

In endometrial cryoablation with Her Option, a cryoprobe is placed into the uterus and cooled with pressurized carbon dioxide to create temperatures of –100° to –120°C.

Advance the cryoprobe into the endometrial cavity (see the image below), typically starting with the tip of the probe at one cornu. Activate the device. This cools the probe to –90°C, which results in the formation of an elliptical ice ball that measures approximately 3.5-5 cm. Each of these freeze cycles is followed by a thaw cycle. The process takes 4-6 minutes and is repeated at the contralateral cornu. It may be repeated in the lower uterine segment.

As a rule, 2 to 3 ice balls are adequate for complete treatment, but the number of ice balls can be increased, depending on the total size of the endometrial cavity. A temperature of –20°C is required for permanent destruction, and this is achieved at 3-5 mm from the edge of the ice ball, where the temperature increases to a nondestructive 0°C.

Monitor the procedure via transabdominal ultrasonography. Monitor the edge of the ice ball to ensure that it does not traverse the uterine serosa. Total procedure time is up to 20 minutes.

Of the GEA devices described in this article, Her Option confers the deepest tissue penetration (up to 9-12 mm) with probably the least discomfort; freezing techniques generally result in less pain than heat-employing techniques. A significant advantage of this device includes the ability to observe tissue destruction ultrasonographically, though such observation can be compromised in obese patients. Performing the procedure with a full bladder can help with visualization, as can intrauterine saline instillation.

Placement of the initial freeze at the fundus prevents the operator from having to attempt to move the probe through an ice ball. Increasing the cornual freeze times may be necessary to achieve the proper depth of tissue destruction. Like hydrothermablation, endometrial cryoablation is not limited by the size of the uterus.

Hydrothermal ablation

Hydrothermal ablation is the only second-generation ablation technique that uses hysteroscopy during treatment. The device is a closed-loop system in which heated saline circulates freely in the uterine cavity and is monitored hysteroscopically. A sheath is placed over a standard 3 mm hysteroscope to provide fluid recirculation. A computerized system controls the cycles, which consist of a priming cycle and a treatment cycle.

Advance the hysteroscope with sheath into the lower uterine segment (see the image below), and instill room-temperature saline into the cavity using gravity to create a low distending pressure (ie, well below 70 mm Hg, which is the approximate opening pressure of the fallopian tubes). During the priming cycle, the fluid is circulated in the uterine cavity for 2 minutes.

Once activated, the device preheats the circulating fluid to 80-90°C, which takes approximately 3 minutes. Again, the pressure should be maintained at 40-50 mm Hg to prevent fluid exiting through the fallopian tubes. A 10-minute treatment phase follows, during which the system shuts down if a deficit larger than 10 mL or a gain larger than 20 mL is measured. This phase is followed by a 1-minute cooldown phase, during which the fluid is at 45°C.

The entire procedure is performed under direct hysteroscopic visualization; it is the only GEA device that allows such visualization during the ablation phase. Total operating time is approximately 20 minutes. One advantage of hydrothermal ablation is that it is effective in irregularly shaped uterine cavities, because the water will contact all surfaces. At present, this device is the only one approved by the US Food and Drug Administration (FDA) for ablation of abnormally shaped endometrial cavities.

The procedural success of hydrothermal ablation is partially dependent on achieving a proper watertight seal at the level of the cervix. The manufacturer produces an extra ridged sheath attachment that is designed to ensure a proper seal. Another method of ensuring a proper seal is to apply a single-toothed tenaculum at the 3 o’clock or 9 o’clock position (or both) for further cervical compression. If automatic shutoff of the device should occur (for the reasons cited above), repeating the procedure is generally not recommended.

Bipolar energy ablation

The NovaSure system consists of a disposable handpiece and a computerized electrosurgical generator. First, sound the uterine cavity, paying particular attention to the length of the cervix (from external os to internal os) and the total length of the uterus. Calculate the cavity length by subtraction, and enter this number into the controller. A slide lock on the handpiece allows the operator to preset the mesh deployment depth (ie, cavity length). The maximum cavity length possible is 6.5 cm.

Using the measured depth of the uterine cavity, advance the device to the uterine fundus, retract it 1 cm, and deploy the bipolar mesh (a metallic, gold-plated grid) by squeezing the main handle of the handpiece until the handle locks into the open position (see the image below).

Manipulate the handpiece as necessary until the most distal portion of the mesh is at its widest possible measurement within the cavity (as measured by the rotary dial at the back end of the handpiece). Manipulations that may be used to achieve full deployment of the radiofrequency (RF) array may include gentle back-and-forth movements of the operator’s end of the device in any of the following directions: from one side to the other, from anterior to posterior, from clockwise to counterclockwise, and, with caution, in and out.

Submucosal myomas, even if smaller than 2 cm, can significantly impair the deployment of the array. Consequently, it is the author’s practice first to partially or fully resect these myomas hysteroscopically.

Enter the cavity width into the controller. Advance the cervical collar to the external os, and lock it in place to create a seal. Use the controller to perform a cavity assessment by initially insufflating a small amount of carbon dioxide into the cavity, ensuring that pressure can be maintained for 4 seconds (to rule out uterine perforation). The current version of this device includes a safety feature that prevents the overriding of the cavity assessment function, thus precluding ablation if the uterus does not pass the cavity assessment.

Apply suction to the cavity, drawing it into contact with the mesh. This allows the removal of blood, charred endometrium, and vapor at the same time. ^[48] These 3 factors can increase impedance and potentially reduce the depth of energy penetration.

During the ablation phase, the generator applies up to 180 W of bipolar power (automatically calculated by the controller on the basis of the previously entered parameters). This phase generally lasts 1-2 minutes. The device ablates to a resistance of 50 ohms or a total of 2 minutes, whichever comes first. This results in desiccation to a depth of 4-5 mm.

The procedure is performed blindly, and total operating time is approximately 10-15 minutes. An advantage of bipolar energy ablation is that it has equal efficacy whether pretreatment of the endometrium is undertaken or not, which makes it ideal for patients who are unable or unwilling to undergo preoperative hormonal treatment.

Microwave ablation

In microwave endometrial ablation, microwave energy (30 W at a frequency of 9.2 GHz) is applied to the endometrium with a transcervical probe that moves through the endometrial cavity. The microwave endometrial ablation device is the only GEA device approved by the FDA for use in the presence of submucosal leiomyomas up to 3 cm and cavity lengths up to 12 cm.

Advance the probe to the fundus, typically starting at one cornu. Activate the system, creating a temperature of 75-85°C that penetrates to a depth of 6 mm. Move the probe from side to side while slowly treating the entire cavity from fundus to the lower uterine segment (see the image below). Safety mechanisms prevent ablation if the probe has not yet been placed into the uterus, if the probe is advanced further than the original sounding, or if an abnormal rise in temperature (possibly due to perforation) is detected. Total treatment time is 2-5 minutes.

With this procedure, it is recommended that the patient not undergo mechanical dilation and curettage beforehand. However, ultrasonography (to document a transmural thickness of at least 1 cm) and hysteroscopy are recommended before the procedure.

Unique to the microwave endometrial ablation device is the thermocoupler, which gives the operator ongoing feedback regarding the temperature at the point of ablation. This is particularly useful in targeted treatment of submucosal myomas, the thorough ablation of which is monitored through both tactile and thermal feedback.

The risk of individual complications from endometrial ablation varies according to the technique used. All forms of ablation carry the risks discussed below. ^[49]

Generally, patients can expect to experience postoperative cramping, minor-to-moderate vaginal bleeding, vaginal discharge, nausea, or a combination of these symptoms. Cramping is typically short-lived, lasting from a few hours to a few days, and is generally controlled with oral analgesics. Most bleeding tapers quickly and transitions to a clear, watery discharge lasting up to 2 weeks. Any foul odor or discoloration of the discharge should prompt evaluation for possible infection.

More specifically, possible complications of endometrial ablation include the following:

• Injury to cervix and vagina

• Uterine injury

• Postablation tubal syndrome

• Pregnancy

• Bleeding

• Cervical stenosis

• Infection

• Hematometra, likely secondary to occlusion of the endocervical canal at the cervicouterine junction

Injury to cervix and vagina

Injury to the cervix or vagina occurs most often during insertion of the ablation device. Injury to the cervix can be decreased by using mechanical dilators or misoprostol to soften the cervix before the procedure. Injury to the vagina most often occurs with the use of monopolar devices and can be avoided with the use of bipolar resectoscopes and careful technique.

Uterine injury

The primary concern is for uterine perforation, which may result in injury to surrounding structures and vasculature. The incidence of uterine injury is reported to be 3-25 per 1000. ^[3] If perforation occurs with an activated electrode, an exploratory laparoscopy or laparotomy is recommended to evaluate the abdominal cavity.

Postablation tubal syndrome

Postablation tubal syndrome, which develops in 6-10% of patients, occurs in women who have previously undergone tubal ligation. Patients present with cyclic pelvic pain and amenorrhea, remote from the procedure. The average time for the development of this complication is within 2-3 years of the ablation procedure. ^[4] The pain is related to trapped menstrual blood from residual endometrium at cornua. Hysterectomy is often the most effective treatment.

Pregnancy

Although infertility can occur after endometrial ablation, the procedure should not be viewed as a sterilization procedure, and patients should be counseled to use an appropriate contraception method. Pregnancies after endometrial ablation are rare, but when they occur, they may be associated with high rates of malpresentation, prematurity, placenta accreta, and perinatal mortality. ^[3]

Bleeding

Bleeding is most commonly encountered with uterine or cervical laceration. Delayed bleeding can develop as a result of endometrial sloughing. Blood coagulation studies should be obtained in cases of late postoperative bleeding, especially if these studies were not obtained preoperatively.

Cervical stenosis

Cervical stenosis may occur if the internal cervical os is also ablated with the endometrium. This complication may be treated with cervical dilatation.

Infection

The infection rate with all endometrial ablation techniques is approximately 1%. Prophylactic antibiotics are not required.

Risks associated with REA procedures

Because REA procedures require the use of a distention medium, potential fluid overload is a concern. Accordingly, careful attention must be paid to the amount of fluid infused, regardless of the type of medium used. A positive infusion balance of 800 mL can result in fluid shifts, possibly leading to pulmonary or cerebral edema.

Electrolyte imbalance is another risk. In REA procedures, low-viscosity fluids (eg, normal saline, glycine, and mannitol) are primarily used as distention media. Vascular absorption of such media can cause acute hyponatremia and a hypo-osmolar state, which can lead to cerebral edema.

Risks associated with GEA procedures

Unlike REA techniques, which rely on the instillation of hypertonic solutions into the endometrial cavity, GEA techniques do not carry the risks of fluid overload and electrolyte disturbance. Although complications rates are low overall, the potential major complications are grounds for concern and warrant strict adherence to the safety measures recommended by each device manufacturer. Many of these devices include safety mechanisms that prevent operator override of automatic shutdown protocols.

Complications secondary to uterine perforation or extravasation of hot fluid, resulting in bowel injury, are the most common major complications reported. ^[28] Hydrothermal ablation has also been reported to cause major burns to the vagina, buttocks, and thighs, secondary to leakage of hot water through the cervix. ^[50]