INTRODUCTION — The introduction of non-resectoscopic ablation techniques has greatly increased the use of endometrial ablation as a therapeutic option for patients with abnormal uterine bleeding. Non-resectoscopic endometrial ablation is performed with a device that is inserted into the uterine cavity and delivers energy to uniformly destroy the uterine lining. Non-resectoscopic techniques are also referred to as second generation ablation.

Resectoscopic endometrial ablation techniques, on the other hand, are performed under hysteroscopic visualization, using resectoscopic instruments to ablate or resect the endometrium. Non-resectoscopic endometrial ablation techniques are more widely practiced than resectoscopic ablation, since they require less specialized training and have a shorter operative time [1].

Non-resectoscopic techniques for endometrial ablation will be reviewed here. General principles (eg, indications, contraindications, preoperative and postoperative care) of endometrial ablation, techniques for resectoscopic endometrial ablation or resection, as well as other management options for abnormal uterine bleeding, are discussed separately. (See "Overview of endometrial ablation" and "Endometrial ablation or resection: Resectoscopic techniques" and "Abnormal uterine bleeding: Management in premenopausal patients".)

CURRENT NON-RESECTOSCOPIC ABLATION DEVICES — Current non-resectoscopic endometrial ablation technologies approved for use in the US by the Food and Drug Administration (FDA) are:

●Bipolar radiofrequency (NovaSure).

●Hot liquid filled balloon (ThermaChoice; no longer available in the United States).

●Cryotherapy (Her Option, Cerene).

●Circulating hot water (Hydro ThermAblator).

●Microwave (Microwave Endometrial Ablation; no longer available in the United States).

●Combined thermal and bipolar radiofrequency (Minerva).

●Vapor ablation (Mara). This device was approved by the FDA in 2017 [2].

Two other brands of hot liquid filled balloon devices are available outside of the United States: Cavaterm and Thermablate EAS.

GENERAL OPERATIVE TECHNIQUE — Positioning, sterile preparation, and cervical dilation are the same as for hysteroscopy. (See "Overview of hysteroscopy", section on 'Procedure'.)

General perioperative practices (eg, endometrial preparation, prophylactic antibiotics) and complications of endometrial ablation, as well as comparison with resectoscopic ablation, are discussed separately. (See "Overview of endometrial ablation", section on 'Complications' and "Overview of endometrial ablation", section on 'Non-resectoscopic versus resectoscopic ablation'.)

Routine use of hysteroscopy — Most non-resectoscopic techniques do not require hysteroscopy, with the exception of the Hydro ThermAblator, during which hot water is instilled into the uterus through a hysteroscopic sheath. For other techniques, preoperative hysteroscopy is necessary only if the uterine cavity has not been assessed for leiomyomas or endometrial polyps in the preoperative period. Also of note, the manufacturer of the microwave ablation system advises hysteroscopic evaluation before and after ablation [3].

The endometrial cavity should be assessed preoperatively in all patients undergoing endometrial ablation. Performing this assessment of the uterus during the preoperative evaluation is optimal, since it helps to guide surgical planning (eg, preparing for myomectomy if a submucosal fibroid is present). If the uterine cavity has not been assessed preoperatively, a diagnostic hysteroscopy should be performed just prior to the ablation procedure. (See "Overview of endometrial ablation", section on 'Assessment of the uterus'.)

Postoperative hysteroscopy is potentially useful to identify areas of remaining endometrium or detect uterine perforation. Some surgeons ablate endometrial remnants using resectoscopic instruments. However, the clinical benefit of hysteroscopy for these indications is uncertain. There are no data regarding whether small amounts of residual endometrium following non-resectoscopic ablation impact treatment success; data suggest that partial resectoscopic ablation is successful [4,5]. (See "Overview of endometrial ablation", section on 'Cavity size'.)

Regarding uterine perforation, evaluation for this complication after blind transcervical procedures is usually performed only in selected patients in whom there is reason to suspect perforation (eg, an instrument was inserted past the depth of the uterine fundus). (See "Uterine perforation during gynecologic procedures", section on 'Diagnosis'.)

ABLATION METHODS — This section will review the energy sources and technical specifications for current non-resectoscopic endometrial ablation devices. Uterine requirements and operative duration for each procedure are listed in the table (table 1). In general, endometrial destruction is achieved when the tissue is heated to 65°C or cooled to -60°C.

Bipolar radiofrequency — The bipolar radiofrequency device (NovaSure) is a three-dimensional bipolar mesh probe that delivers radiofrequency current (a type of electrical energy) until a specific tissue impedance is reached (figure 1A-B). The NovaSure generator applies up to 180 watts of power.

The device is inserted into the uterine cavity and the mesh is expanded until it is in contact with the endometrium. Suction is then applied to the endometrial cavity, thereby drawing the endometrium closer to the bipolar mesh probe. The suction also removes debris and vapor that can increase impedance and reduce the depth of energy penetration. The system will shut down when complete desiccation has occurred (calculated at a tissue impedance of 50 ohms of resistance) or after a total treatment time of two minutes. The average treatment time is just over one minute and the average depth of ablation is 4 to 5 millimeters.

The system also evaluates cavity integrity by emitting carbon dioxide and assessing for leaks. If the integrity check fails, the user will not be able to activate the ablation phase of the procedure.

Uterine requirements — Uterine cavity and cervical dilation parameters for NovaSure ablation are [6]:

●Diameter of the original NovaSure device is 8 mm, and the diameter of the NovaSure Advanced device is 6 mm.

●Sounded cavity length ≥6 to ≤10 cm; alternatively, ≥4 cm from internal cervical os to fundus.

●Cornua to cornua distance ≥2.5 cm.

●Patients with submucosal leiomyomas or with endometrial polyps >2 cm were excluded from the FDA approval studies.

●No irregularly shaped cavities.

Intraoperative predictors for failure of radiofrequency endometrial ablation were evaluated in a retrospective cohort study (n = 1178) [7]. Failure was defined as subsequent development of abnormal uterine bleeding, pelvic pain, or dysmenorrhea that necessitated surgical intervention or medical intervention. Predictors for ablation failure were uterine sounding length >10.5 cm (2.6-fold increased risk), uterine cavity length (from fundus to endocervix) >6 cm (twofold), uterine width >4.5 cm (twofold), uterine surface area (uterine cavity length multiplied by uterine width) >25 cm² (twofold), procedure duration <93 seconds (2.6-fold), and radiofrequency ablation index (procedure duration divided by the surface area) (3.1-fold).

Outcome — Studies in which patients who underwent NovaSure ablation were followed for five or more years reported high rates of reduced uterine bleeding (97 to 98 percent) and amenorrhea (75 to 97 percent) [8,9]. There were low rates of repeat ablation (1 to 4 percent) and hysterectomy (3 to 8 percent).

Advantages/disadvantages — NovaSure ablation does not require endometrial preparation, since it adjusts ablation depth by measuring tissue impedance. This may increase the ease of scheduling in comparison with other endometrial ablation techniques. (See "Overview of endometrial ablation", section on 'Endometrial preparation'.)

NovaSure was not evaluated in the FDA approval studies for use in patients with intracavitary fibroids. However, some data suggest that bipolar radiofrequency ablation is successful in this population. A prospective series of 65 patients with endometrial polyps or fibroids up to 3 cm who underwent bipolar radiofrequency ablation reported, at one-year follow-up, that 95 percent had improvement in uterine bleeding [10].

Cryoablation — Cryoablation is a technique in which a cryoprobe is inserted into the uterine cavity (figure 2A-B). The probe is cooled either by liquid nitrogen or by differential gas exchange. An elliptical ice ball approximately 3.5 by 5 centimeters forms around the probe when it is cooled to less than -90°C. At the edge of the ice ball, the tissue temperature is 0°C, which is nondestructive. A temperature of -20°C is lethal to tissue; this temperature is reached approximately 3 to 5 mm from the edge of the ice ball. Therefore, the endometrial tissue exposed to this low temperature, including the basalis layer of the endometrium (figure 3), is permanently destroyed.

The number of ice balls that must be created to destroy the entire uterine cavity is dependent upon the size of the cavity. Intraoperative ultrasonography is used to monitor probe placement and depth of tissue freezing. In general, two to three ice balls are sufficient (figure 4). Each freeze cycle takes two to six minutes.

Uterine requirements

●Uterine parameters for Her Option ablation are [11]:

•Diameter of device 5.5 mm.

•Sounded cavity length ≥4 to ≤10 cm.

•Patients with intramural leiomyomas ≤2 cm in diameter were included in the FDA approval studies; patients with pedunculated fibroids or endometrial polyps were excluded.

●Uterine parameters for Cerene are [12]:

•Cervix should be dilated to 6 mm.

•Sounded cavity length ≤10 cm (uterine cavity length: >2.5 but <6.5 cm).

•Patients with an endometrial polyp >1 cm in diameter, any submucous fibroids, or any intramural fibroids that distorted the uterine cavity were excluded in the FDA approval studies.

Outcome — A randomized trial compared Her Option with rollerball ablation in 279 patients [13,14]. There were few adverse events; major complications included, in the Her Option group, one patient who underwent a hysterectomy 43 days after the procedure for severe uterine bleeding and one patient who was treated with rollerball was hospitalized for hematometra. At two-year follow-up, patients in the Her Option group compared with the rollerball group had similar rates of either reduced uterine bleeding or amenorrhea (94 versus 92 percent). Rates of hysterectomy (7 and 8 percent) and repeat ablation (3 and 1 percent) were similar between groups.

The Cerene device was evaluated in a prospective, multicenter, single-arm study including 242 patients (mean age 40.1 years) undergoing treatment for heavy menstrual bleeding (HMB); there were no reported major adverse device effects or major adverse events [15]. The primary effectiveness endpoint (reduction of bleeding at 12 months) was achieved in 77 percent of patients and the majority (90 percent) of patients were satisfied or very satisfied with their outcome; outcome results were not available for eight patients. Four patients (1.7 percent) required further intervention (medical or surgical) for continued HMB.

Advantages/disadvantages — Use of cold destroys tissue and may also cause numbness. Therefore, cryoablation is potentially less painful than the other non-resectoscopic techniques, which all use high temperatures. Less perioperative pain is an advantage for use with no anesthesia or with local anesthesia.

Another unique feature of cryoablation is the use of perioperative sonography. This serves as both an advantage and disadvantage. Cryoablation is not a totally blind procedure, which helps to ensure complete ablation and avoid complications. On the other hand, it can be difficult to visualize the ice ball if the patient is obese and the need for sonography adds to the expertise and/or personnel required to perform the procedure.

An advantage of the Cerene device is the absence of postoperative intrauterine synechiae and the ability to evaluate the endometrium after treatment. In the prospective study described above (see 'Outcome' above), of the 223 patients who underwent hysteroscopy 12 months after their Cerene cryoablation procedure, complete evaluation of the uterine cavity was possible in 204 out of 220 (93 percent) patients; uterine cavity entry was not possible in three patients due to pain intolerance or cervical stenosis [15].

Circulating hot water (hydrothermal) — Hydrothermal ablation (Hydro ThermAblator [HTA]) refers to a technique in which a hysteroscope sheath is inserted into the uterine cavity under direct hysteroscopic visualization (figure 5). Heated isotonic saline is administered into the uterus through the sheath. To maintain a low uterine distension pressure (<70 mmHg), the fluid is instilled using gravity rather than a pump. The treatment phase lasts for 10 minutes, during which the fluid should be at a temperature of 90°C. An intrauterine cool down phase is then performed for one minute with the fluid at 45°C.

Safety apparatus within the equipment detects whether any fluid has escaped from the closed system, which will shut down if more than 10 cc of fluid are lost, whether through the cervix, fallopian tubes, or a uterine perforation.

Uterine requirements — Uterine cavity and cervical dilation parameters for HTA ablation are [16]:

●Diameter of device 7.8 mm.

●Sounded cavity length ≥6 to ≤10.5 cm.

●Patients with submucosal fibroids were excluded in the FDA approval studies.

Outcome — A randomized trial compared HTA with rollerball in 276 patients [17,18]. Patients treated with HTA compared with rollerball were less likely to have postoperative hematometra (1 versus 6 percent), but they were significantly more likely to experience abdominal pain (53 versus 38 percent) and postoperative nausea and vomiting (22 versus 7 percent). Two patients in the HTA group had lower extremity burns due to contact with the device tubing.

At three-year follow-up, patients in the HTA group compared with those in the rollerball group had similar rates of reduced uterine bleeding (94 versus 91 percent) and amenorrhea (53 versus 46 percent). For HTA compared with rollerball, rates of hysterectomy were 9 and 6 percent and of repeat ablation were 2 and 4 percent. Tests of significance were not reported for the three-year follow-up data.

Advantages/disadvantages — The primary advantage of this method is that it can be performed in patients with intracavitary lesions. The circulating hot water will contact the entire endometrial surface regardless of cavity irregularity (figure 6). There is a report of use of HTA in two patients with bicornuate uteri, but ablation in patients with uterine anomalies is not standard practice [19]. (See "Overview of endometrial ablation", section on 'Uterine anomalies'.)

Another advantage of HTA is that it is done under direct visualization, so the operator can ensure that the entire uterine lining has been destroyed.

Perioperative pain is a potential disadvantage of HTA. The hysteroscope used has a large diameter (7.8 mm) and hot water stimulates pain from nerve fibers within the myometrium.

In addition, external burns appear to be more frequent following HTA than other non-resectoscopic ablation procedures. There have been reports of vaginal, perineal, and leg burns from contact with hot water when there was a poor seal on the cervix or when the sheath was removed before the intrauterine fluid has cooled [20-22]. From 2003 to 2006, voluntary reports by device manufacturers to the FDA Manufacturer and User Facility Device database regarding circulating hot water ablation included 54 cases of burns (22 were major burns); it is not possible to calculate the incidence of these injuries, since the total number of procedures performed during this time period is not known [23].

Combined thermal and radiofrequency ablation — A combined thermal and radiofrequency ablation endometrial ablation device (Minerva) was approved by the FDA in 2015 [24]. The mechanism of ablation utilized by the device is mainly heat applied to the endometrium via a silicone membrane with circulating ionized argon gas (the argon gas is heated by radiofrequency current) [25]. In addition, heat is applied to the endometrium by intracavitary fluid produced and retained during the procedure that is heated by the silicone membrane and by direct effects of radiofrequency current on the endometrium.

Uterine requirements — Uterine cavity parameters for combined radiofrequency and thermal ablation are [24]:

●Cervix should be dilated to 7.0 mm.

●Uterine cavity length ≥4 cm.

●Contraindicated in a patient with a narrow uterine cavity – Narrow was not defined in the device instructions, but a cavity width of <2.5 cm was an exclusion criterion in a preclinical study [25].

●Contraindicated in a patient with a prior endometrial ablation by any method.

●Patients with fibroid(s) distorting the uterine cavity or large endometrial polyp(s) (>2 cm) were excluded from preclinical studies [25,26].

Outcome — Studies of the device include:

●A multicenter, single-arm, randomized trial (n = 153) of premenopausal patients with heavy menstrual bleeding assigned to endometrial ablation with the Minerva device or rollerball [26]. At one year, thermal/radiofrequency compared with rollerball resulted in higher rates of menstrual blood volume ≤80 mL (93.1 and 80.4 percent) and amenorrhea (71.6 and 49 percent). There were no intraoperative complications.

●A multicenter prospective study (n = 105) of premenopausal patients with menorrhagia and dysfunctional uterine bleeding treated with Minerva ablation reported that at one year, 96.2 percent achieved a target reduction of menstrual bleeding based on a pictorial blood loss assessment chart and 69.5 percent were amenorrheic [25]. No intraoperative complications were reported.

Advantages/disadvantages — The main advantage of the combined thermal and radiofrequency endometrial ablation system is the high amenorrhea rate reported in the randomized trial [26]. Another advantage is the relatively low power setting of approximately 40 watts used with this device. The disadvantage with this device is the lack of data regarding long-term outcomes in terms of hysterectomy rate, or other potential late occurring complications, such as hematometra.

Vapor ablation — The vapor ablation device (Mara) uses water vapor to ablate the endometrium. A disposable handheld device is inserted through the cervix and into the uterus to deliver vapor for 120 seconds to ablate endometrial tissue. To use this system, the vapor probe is inserted inside the uterine cavity, after which three positioning balloons are inflated to seal the uterine cavity. A uterine cavity integrity test is performed to ensure the absence of vapor leaks, and a lumen patency test is performed to confirm that the vapor probe is positioned unobstructed by blood or tissue. Vapor delivery is then delivered for 140 seconds. The first 20 seconds of vapor delivery displaces the remaining saline from the patency test and then ablation is carried out for 120 seconds. During that time, the vapor generator regulates the vapor pressure based on feedback from a pressure sensor near the distal tip of the vapor probe and monitors temperature via a thermocouple on a positioning probe.

Uterine requirements — Uterine parameters for Mara ablation are:

●Sounded uterine cavity length ≥6 to ≤12 cm

●Any uterine width

●Cervical dilation 5.8 mm (usually does not require dilation)

Of note, no International Federation of Gynecology and Obstetrics (FIGO) type 0 or 1 fibroids were included in the pivotal trial, so efficacy is uncertain in patients with such fibroids.

Outcomes — The vapor ablation system was evaluated in a prospective study of 155 subjects. The primary effectiveness end point was a reduction in menstrual blood loss, as measured by a Pictorial Blood Loss Assessment Chart (PBLAC) score of <75 at one year after ablation [27]. At 12 months, 78.7 percent of patients had a PBLAC score <75, and the amenorrhea rate was 19.4 percent. At 12 months, 91 percent of patients were very satisfied or satisfied.

Advantages/disadvantages — The vapor ablation has the advantage of providing a soft, flexible tip for insertion through the endocervical canal that eliminates the requirement to touch the uterine fundus and can essentially be performed without cervical dilation.

Other — The following ablation methods are not available for clinical use in the United States.

Microwave — Microwave Endometrial Ablation (MEA) is a 9.2 GHz, 30 watt, microwave system (figure 7). When inserted into the uterine cavity, this energy will produce a tissue temperature of 75 to 85°C at a depth of 6 mm. In order to treat the entire uterine cavity, the surgeon moves the probe from cornu to cornu and across the lower uterine segment until the entire endometrium has reached the desired temperature. Total treatment time is three to five minutes. Unlike other non-resectoscopic ablation devices, the probe is reusable.

The manufacturer of MEA advises hysteroscopic evaluation before and after ablation, in contrast with other non-resectoscopic ablation devices.

Uterine requirements — Uterine parameters for MEA ablation are [3]:

●Diameter of device 8.5 mm.

●Sounded cavity length ≥6 to ≤12 cm is advised by the manufacturer, although the device was studied in patients with a cavity length of up to 14 cm.

●Patients with submucosal leiomyomas that do not obstruct treatment access were included in the studies for FDA approval.

Outcome — A randomized trial compared MEA with endometrial resection in 263 patients [28,29]. Perioperative complications included a uterine perforation in each treatment group. Excessive intraoperative bleeding occurred in five patients in the resection group and none in the MEA group; however, three patients treated with MEA were readmitted with secondary hemorrhage. In patients followed for 10 or more years, those treated with MEA compared with resection had similar rates of amenorrhea (83 and 88 percent). The rate of repeat ablation was similar in patients treated with MEA compared with resection (1 versus 2 percent); however, the hysterectomy rate differed significantly (17 versus 28 percent).

Advantages/disadvantages — The labeling from the manufacturer of this device includes the treatment of patients with small submucosal leiomyomas (≤3 cm). The uterine cavity size maximum is larger than with the other non-resectoscopic ablation devices (12 to 14 cm versus 10 cm).

The manufacturer of MEA advises extra precautions that are not advised for the other non-resectoscopic devices, including preoperative measurement of the thickness of the myometrium and pre- and postoperative hysteroscopy. These may serve as barriers for the use of this method for surgeons and patients.

These requirements were likely added because prior to the introduction of MEA in the United States, there were case reports from Europe in which bowel burns occurred in patients with no perforation of the uterus [30]. The etiology was presumed to be passage of microwave energy through the uterine walls. As a result, the FDA trial required that ultrasound be performed prior to the procedure and that the myometrium be at least 1 cm in thickness in all areas. The potential risk of ablation-associated injury in patients with thinning of the myometrium is not limited to microwave ablation. (See "Overview of endometrial ablation", section on 'Myometrial thinning following uterine surgery'.)

Hot liquid filled balloons — Hot liquid filled balloon ablation is also referred to as thermal balloon ablation. There are three available brands of hot liquid filled balloons for endometrial ablation. ThermaChoice (figure 8A-B) is FDA-approved and Cavaterm and Thermablate EAS are available only outside the United States.

All three devices utilize a silicon balloon which is inserted through the cervix into the uterine cavity via a probe [11,31,32]. The balloon is expanded to a pressure of 160 to 220 mmHg with either 5 percent dextrose in water (ThermaChoice), glycine (Cavaterm), or glycerine (Thermablate EAS). For ThermaChoice and Cavaterm, the fluid is heated to approximately 68 to 87°C and ablation requires 8 to 10 minutes. Thermablate uses a higher temperature (173°C) and has shorter ablation time (two minutes).

Uterine requirements — Uterine cavity and cervical dilation parameters for ThermaChoice ablation are [11]:

●Diameter of device 5.5 mm.

●Sounded cavity length ≥6 to ≤10 cm.

●Patients with submucosal leiomyomas were excluded from the FDA approval studies.

Outcome — Studies with long-term follow-up report a wide range of treatment results. In patients who underwent hot liquid filled balloon ablation with either ThermaChoice, Cavaterm, or an unspecified device and were followed for four or more years, there was reduced uterine bleeding in 22 to 81 percent and amenorrhea in 23 to 58 percent [33-35]. Repeat ablation was performed in 5 to 11 percent, and hysterectomy in 2 to 13 percent.

It is unclear whether these long-term data apply to current versions of the hot liquid filled balloon devices, since two of the devices have been revised (ThermaChoice III and Cavaterm plus) and Thermablate was introduced later than the other devices and follows a different protocol. For the current version of each of the devices, the reported rates of treatment success and failure are:

●ThermaChoice III – A prospective study of 148 patients followed for 12 months reported reduced bleeding in 31 percent and amenorrhea in 66 percent [36]. No patient had undergone re-ablation or hysterectomy.

●Cavaterm plus – A prospective study of 220 patients followed for 19 months reported reduced bleeding or amenorrhea in 74 to 83 percent [37]. No patient had undergone re-ablation, but 15 percent had undergone, or were planning, hysterectomy.

●Thermablate EAS – A prospective study of 47 patients followed for 12 months reported reduced bleeding or amenorrhea in 77 percent [38]. There were no reports of re-ablation or hysterectomy.

Advantages/disadvantages — Hot liquid filled balloon techniques may cause more perioperative pain than other non-resectoscopic ablation techniques (see 'Perioperative pain' below). The likely mechanism of this is the stimulation of pain fibers by both the heat and uterine distention pressure produced during the procedure. However, with adequate preoperative analgesia (eg, nonsteroidal anti-inflammatory drugs, oral narcotics) and a paracervical block, the procedure can be performed in an office setting in appropriately selected patients.

ThermaChoice was not evaluated in the FDA approval studies for use in patients with intracavitary lesions. However, some data suggest that hot liquid filled balloon ablation is successful in this population. Hot liquid filled balloon ablation was used successfully in 45 patients with submucosal fibroids ≤3 cm in a randomized trial comparing balloon versus rollerball ablation [39,40].

An additional disadvantage is that hot liquid filled balloon techniques cannot be used in patients with intracavitary lesions since ablation occurs only where the balloon is in contact with the endometrium.

While there is one report of successful use of a liquid balloon in a patient with bicornuate uterus, endometrial ablation in patients with uterine anomalies is not standard practice [41]. (See "Overview of endometrial ablation", section on 'Uterine anomalies'.)

CHOOSING AMONG TECHNIQUES — Of the seven non-resectoscopic ablation devices (five of which are available in the United States), all reduce uterine bleeding in 80 percent or more of patients treated. Operative complication rates are low for all seven devices.

In the absence of differences in efficacy and complications, choosing among the non-resectoscopic ablation methods is based upon the following factors:

●Uterine characteristics (cavity size and the presence of intracavitary lesions).

●Factors that facilitate use in an office setting and/or under local anesthesia (eg, operative duration, perioperative pain).

●Ease of preoperative preparation.

●Surgeon familiarity and preference.

●Device availability.

The feasibility of use in an office setting and/or under local anesthesia is of particular importance when deciding among non-resectoscopic ablation techniques. Office use offers benefits of greater patient acceptability, ease of scheduling, and reduced expense. Many surgeons do not have the office set-up to perform ablation; however, use of local anesthesia has fewer risks and adverse effects than general anesthesia, regardless of the operative setting. All non-resectoscopic methods can be performed in an office setting and/or under local anesthesia, but some are more amenable to this approach than others (eg, shorter operative duration, less perioperative pain). (See "Overview of endometrial ablation", section on 'Office versus operating room procedures' and "Overview of endometrial ablation", section on 'Anesthesia'.)

Efficacy and complications — In the few studies that have compared between non-resectoscopic endometrial ablation techniques, radiofrequency and microwave methods were found to have comparable efficacy to hot liquid filled balloon devices, while radiofrequency was found to be superior to circulating hot water ablation [42-47]. Further data are needed to compare among non-resectoscopic ablation techniques.

●Bipolar radiofrequency versus hot liquid filled balloon – NovaSure was compared with ThermaChoice balloon ablation in a randomized trial of 126 patients [42,43,48]. There were no operative complications in either group. At 5- and 10-year follow-up, the NovaSure versus ThermaChoice groups had no significant differences in the frequency of amenorrhea (five years: 48 versus 32 percent), repeat ablation (five years: one patient in each group), or hysterectomy (five years: 10 versus 13 percent).

Similarly, a randomized trial in 57 patients compared NovaSure with the Cavaterm balloon [44]. There were no major complications in either group; perioperative pain was lower in the radiofrequency group. At 12 months, rates of amenorrhea were significantly higher in the NovaSure compared with Cavaterm group (42 versus 12 percent); the rate of eumenorrhea between groups did not show a significant difference (16 versus 29 percent). Among patients treated with NovaSure, three (8 percent) were planning repeat ablation and two (5 percent) underwent hysterectomy.

●Bipolar radiofrequency versus circulating hot water – In a randomized trial of 160 patients with menorrhagia without pretreatment therapy, at 12-month follow-up, NovaSure compared with HTA had significantly higher rates of patient satisfaction (87 versus 68 percent), amenorrhea (47 versus 24 percent) [47]. In addition, NovaSure was associated with one-third the risk of reintervention and one-half the risk of hysterectomy.

●Microwave versus hot liquid filled balloon – The MEA system appears to result in less postoperative pain and nausea than hot liquid filled balloon ablation. This was illustrated in a randomized trial of 320 patients comparing MEA with ThermaChoice III [45]. There were no major complications in either group; patients in the microwave versus balloon group had a significantly lower rate of using postoperative opiates (80 versus 89 percent) or antiemetics were used by fewer patients in the microwave versus balloon group (26 versus 48 percent). At one-year follow-up, there were no significant differences between microwave and balloon ablation in pictorial blood chart assessment scores (3.0 versus 4.0; menorrhagia is defined as ≥100 [46]) or amenorrhea (41 versus 38 percent). No patient underwent re-ablation or hysterectomy.

General complications of resectoscopic and non-resectoscopic endometrial ablation are discussed separately. (See "Overview of endometrial ablation", section on 'Complications'.)

Thermal injury — Burns to the vagina, vulva, or thighs are a rare, but serious, complication that is associated mainly with circulating hot water ablation. Only a few cases of this complication have been reported by device manufacturers to the FDA Manufacturer and User Facility Device database [22]. Further study of the risk of thermal injury with HTA ablation is needed. (See 'Circulating hot water (hydrothermal)' above.)

Use with leiomyomas or polyps — Microwave ablation and cryoablation were evaluated in the FDA approval studies in patients with small submucosal or intramural fibroids; labeling for circulating hot water ablation permits use in patients with submucosal fibroids that are ≤4 cm, although these patients were excluded from the approval studies. A total of 19 patients were included in the FDA pivotal trial for the vapor ablation device; none were FIGO type 0 or 1, two were FIGO type 2, and four were FIGO type 3. Therefore, there are limited data for evaluation with this device.

Endometrial polyps can generally be easily removed prior to endometrial ablation. Of note, patients with small endometrial polyps (≤2 cm) were included in the FDA approval studies for the microwave, bipolar radiofrequency, and ThermaChoice hot liquid filled balloon devices.

Use of endometrial ablation in patients with intracavitary lesions is discussed separately. (See "Overview of endometrial ablation", section on 'Leiomyomas or polyps'.)

The treatment of submucosal fibroid with resection at the time of non-resectoscopic endometrial ablation is understudied. A theoretical concern about resection of a fibroid with subsequent non-resectoscopic ablation includes the transfer of energy through a partially resected fibroid, which may absorb energy differently than myometrium. In a retrospective study of 160 patients ablated with HTA with normal cavities (n = 136) and submucous fibroids (n = 33) without resection, demonstrated a high amenorrhea rate in both groups, thus suggesting fibroid resection was not necessary [49].

Preoperative preparation — Endometrial preparation is advised by the manufacturer used for all non-resectoscopic ablation procedures with the exception of the bipolar radiofrequency and the Mara devices (the Mara device was evaluated in the early proliferative phase). The other device manufacturers advise 30 to 60 days of pretreatment with a gonadotropin-releasing hormone antagonist (eg, intramuscular leuprolide 3.75 mg/month); preparation for ThermaChoice can be either hormonal suppression or uterine curettage.

Endometrial preparation for endometrial ablation is discussed in detail separately. Methods that do not require hormonal suppression avoid the drug-associated 30- to 60-day delay and adverse effects (eg, menopausal symptoms). (See "Overview of endometrial ablation", section on 'Endometrial preparation'.)

MEA ablation requires sonographic measurement of the myometrium in all patients since endometrial ablation in patients with severe myometrial thinning can potentially result in visceral injury. This requirement, however, does not add to the relative inconvenience of the procedure, since uterine imaging is required prior to all non-resectoscopic ablation procedures. (See "Overview of endometrial ablation", section on 'Myometrial thinning following uterine surgery'.)

Endometrial sampling is performed in all patients prior to endometrial ablation to exclude endometrial hyperplasia or cancer. Ideally, this should be performed with enough time to receive the results and cancel the procedure, if neoplasia is found. However, if sampling has not yet been performed by the day of the procedure, it should be done just prior to the ablation. Some clinicians elect to perform a routine dilation and curettage (D&C) at the time of endometrial ablation in addition to the office endometrial sampling. Routine D&C should not be considered necessary in all cases, as this surgery is often performed in the office setting with mild or moderate sedation, which may not be appropriate pain control for D&C. However, it is reasonable to consider a D&C if there is adequate pain control, and if there is concern about the accuracy of the office endometrial sampling, or if there are additional risk factors for endometrial hyperplasia or endometrial cancer, as clearly, there are cases of endometrial ablation in patients with existing endometrial cancer. For example, in a systematic review of endometrial cancer after endometrial ablation, 22 cases of endometrial cancer were found, the time of diagnosis ranging from two weeks to 10 years postoperatively [50].

Operative duration — A shorter procedure is easier for a patient to tolerate under local anesthesia. Also, differences in operative duration impact upon a surgeon's operative or office schedule.

The duration of energy delivery of the non-resectoscopic endometrial ablation procedures, from shortest to longest, are:

●NovaSure bipolar radiofrequency (90 to 120 seconds)

●Minerva thermal/radiofrequency (120 seconds)

●Mara vapor system (120 seconds)

●Cerene cryoablation (2.5 minutes)

●MEA (3 to 5 minutes)

●ThermaChoice hot liquid filled balloon (8 minutes)

●HTA circulating hot water (10 minutes)

●Her Option cryoablation (10 minutes)

Thermablate EAS hot liquid filled balloon ablation has an operative time of just two minutes, but it is not currently available in the United States.

These times do not include other parts of the procedure, which are similar across ablation methods, including patient set-up and anesthesia time.

Perioperative pain — There are few comparative data regarding perioperative pain across non-resectoscopic endometrial ablation methods [51]. Bipolar radiofrequency ablation and MEA appear to be associated with less perioperative pain than hot liquid filled balloon procedures, based on data from randomized trials [44,45,51].

Pain is stimulated by cervical dilation, uterine distention and burning of the endometrium. The ThermaChoice hot liquid filled balloon and cryoablation devices use probes with the smallest diameter (approximately 5 mm), which require no or minimal cervical dilation. No uterine distention is required with the bipolar radiofrequency, cryoablation, and microwave devices. Her Option and Cerene provide cryoanesthesia while all other devices use heat to burn the endometrium, which stimulates pain fibers within the endometrium and myometrium. Taking into consideration all sources of pain, the cryoablation device likely results in the least amount of perioperative pain, although comparative data are needed to fully evaluate this.

Summary — All of the endometrial ablation devices have similar efficacy and complication rates and each device has advantages and disadvantages. Cryoablation appears to result in the least patient discomfort. Bipolar radiofrequency, thermal/bipolar radiofrequency, and vapor ablation have the shortest energy delivery time. Circulating hot water is the only non-resectoscopic method performed using direct visualization. Surgeons should determine which device is most appropriate in their practice.

In patients with submucosal fibroids or endometrial polyps, we suggest use of microwave ablation or cryoablation over other methods since the success of the other devices was not evaluated in the FDA studies. Although radiofrequency ablation and hot liquid filled balloon ablation were not initially evaluated in patients with intracavitary lesions (submucosal fibroids, endometrial polyps), some data suggest that these methods can be used effectively in this population. Limited data are available for the vapor ablation with fibroids. Further study of this issue is needed. By contrast, microwave has been evaluated and used successfully in these patients. Microwave ablation has the additional advantage of allowing for a larger cavity size than other methods (12 to 14 versus 10 cm). (See 'Bipolar radiofrequency' above and 'Circulating hot water (hydrothermal)' above and 'Microwave' above.)

POSTOPERATIVE CARE — Postoperative care and other follow-up issues for endometrial ablation is discussed separately. (See "Overview of endometrial ablation", section on 'Follow-up'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Gynecologic surgery".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topic (see "Patient education: Endometrial ablation (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Non-resectoscopic endometrial ablation is a treatment for abnormal uterine bleeding that is performed with a device which is inserted into the uterine cavity and delivers energy to uniformly destroy the uterine lining. (See 'Introduction' above.)

●Comparative studies have found comparable treatment efficacy for bipolar radiofrequency, microwave, and hot liquid filled balloon ablation devices. (See 'Efficacy and complications' above and 'Perioperative pain' above.)

●The non-resectoscopic endometrial ablation devices with the shortest energy delivery times are bipolar radiofrequency (90 to 120 seconds), thermal/bipolar radiofrequency (120 seconds), vapor ablation system (120 seconds), and microwave (one to four minutes); hot liquid filled balloon device with an operative duration of two minutes is available outside of the United States. (See 'Operative duration' above.)

●In patients with small (≤4 cm) submucosal fibroids or endometrial polyps, we suggest use of microwave ablation or cryoablation rather than other non-resectoscopic ablation methods (Grade 2C). Patients with larger intracavitary lesions require resectoscopic endometrial ablation or other treatment methods. (See 'Microwave' above.)

●All of the non-resectoscopic devices appear to have similar efficacy and complication rates. Specific methods have advantages or disadvantages regarding operative duration, perioperative pain, and use in patients with irregular uterine cavities. (See 'Choosing among techniques' above.)