The studies diverged regarding the devices, parameters, temperature applied to vaginal tissue, form of application, and number of sessions. RF can be divided into ablative, microablative, and non-ablative, monopolar and bipolar, according to energy dissipation and the action of the electromagnetic wave on the tissue. Non-ablative monopolar RF has been found to be the most widely used [1] . The monopolar form passes from an active electrode conductor handled by the operator to the body, exiting by passive electro (grounding). The advantage is that the energy concentrates in a small and precise area, besides requires handling of only one part. In the bipolar form, both electrodes are located on the operator's handle, so the energy flows directly from one electrode to the other, and this increases the ability to concentrate the energy, generating a thermal effect on the tissue. Bipolar technology allows, through the distance between the two electrodes, greater control and uniformity of RF, but with less penetration and depth of energy [5] .

Microablative RF promotes the discharge of fractional electromagnetic energy causing evaporation of the cell and the consequent protein denaturation of the tissue. It uses 0.2 mm long micro-needles that generate microscopic columns of ablative thermal lesions in the epidermis and upper dermis [6] [7] .

The monopolar protocols varied according to the papers reviewed [1] . Those that described temperature cited a range of 39˚C to 45˚C in the transvaginal transducer. Others applied energy by dividing the vagina into quadrants and others only to the urethral meatus and anterior wall of the vagina. One study used a temperature of 43˚C with the patient in the lithotomy position for a period of 7 to 10 minutes, applying energy to the entire anterior vaginal wall and vaginal introitus for three sessions at 4-week intervals [8] . Another study used monopolar non-ablative RF with the temperature set at 41˚C while maintaining circular movements for two minutes in the anterior and posterior vaginal walls for five sessions at 7-day intervals [9] . The studies that used bipolar RF applied energy only to the anterior wall of the vagina and vaginal introitus, adjusting the temperature to 43˚C for a period of seven to ten minutes, for two or three sessions with an interval of four weeks [8] [10] . In the non-ablative modality, the use of topical anesthetic is not necessary. The microablative protocol consists of applying lidocaine to the vaginal walls and introitus and antisepsis. Application of RF under direct vision on the anterior and posterior walls and vaginal introitus, for three sessions at 30-day intervals, recomendation to use barrier cream for two to five days after treatment, and avoid sexual intercourse for 10 days [6] [7] .

The primary outcomes analyzed were based on the response to quality of life questionnaires (ICIQ-SF). Pinheiro et al., in a pilot study with 11 postmenopausal women, showed that among six participants with pre-treatment urinary complaints, at the end of three months of intervention, 5 (83.3%) had shown improvement in the score, with two participants referring complete improvement. However, two participants had a higher score at the end of the treatment; among these, one started with symptoms of urinary loss after the first session [9] .

Mezzana et al. in a non-controlled retrospective study with 54 women ranging in age from 40 to 71 years (mean, 70.1 years) using bipolar RF grouped the participants into a scale of SUI severity: 7 (13%) mild, 33 (61%) moderate and 14 (26%) severe. At the follow-up visit, 4 months after treatment, participants’ symptomatology improved: 35 (65%) had mild SUI, 18 (33%) moderate and 1 (2%) severe [10] .

Abdelaziz et al, in a retrospective study comparing bipolar vs. monopolar RF treatment in women with different types of UI, evaluated 69 women, with ages ranging from 35 to 79 years, applying the UDI-6 questionnaire. Both RF modalities were effective in improving UI-related quality of life scores, included at 6 months post-treatment. In subgroup analysis by UI types (stress incontinence, urge incontinence, mixed incontinence), there was consistent improvement in all three groups of incontinence with no statistical difference favoring one group over other. A limitation of the study, as a retrospective study, a true power analysis was not performed, statistical analysis was hampered [8] .

Slongo et al. in a randomized clinical trial with 117 climateric women with SUI, compared microablative RF to pelvic floor muscle exercises (PFME) in three intervention groups: group 1 microablative RF and 3 monthly sessions; group 2 PFME with 12 weekly sessions; and group 3, simultaneous RF and PFME. The participants were evaluated before treatment and 30 days after the final treatment session. Urinary loss was evaluated with the ICIQ-SF questionnaire and a 1-hour pad test to quantify urinary loss. The three groups showed statistically significant improvement in the score of the questionnaire after treatment, and the RF + PFME group presented the most marked and significant reduction in the urinary loss, with reduction from 13.6 ± 3.8 to 8.2 ± 5.2. All groups also presented a change in the classification of urinary loss in the pad test analysis, from important to insignificant. It is worth mentioning the fact that the follow-up loss rate in the PFME group was 33.3%, while in the other groups it was 7.6% [6] .

A systematic review demonstrated that RF treatment, either non-ablative or micro-ablative, had an objective improvement in volume reduction in the pad test. However, it draws attention to the design of the studies, since few are randomized and with control groups or sham procedures. In addition, those studies present small samples—only one study presented a sample with more than 100 participants, and they also present a short follow-up period, since only one presented a 12-month follow-up [1] .

Non-urinary outcomes include the effects of RF on vaginal epithelium, vaginal dryness and sexual function. In a study of non-ablative RF with 11 patients, improvement of GSM symptoms was reported with regard to sexual function. Following the analysis of the FSFI questionnaire, which was interpreted in terms of total score, assessing the overall quality of women’s sexual performance/satisfaction, all participants showed sexual dysfunction in the pre-treatment phase. Nine of them (81.8%) showed improvement in the score, with 3 of these women no longer showing a result consistent with sexual dysfunction. After 3 months of exposure, the benefit was sustained in 72% of the participants. Most participants showed no improvement in pH (63.6%) and three showed a decrease in pH, meaning improvement in vaginal health [9] .

Slongo et al. when analyzing the symptoms of GSM, observed that the three therapies were successful according to ICIQ-VS. The RF group achieved the most significant improvement in reducing symptom score (−9.3) compared to the RF + PFME group (−4.4) and the PFME group (−3.4). Vaginal dryness, hydration, pH, and vaginal elasticity showed improvement in the groups that used RF, regardless of the association with PFME. The FSFI scores improved significantly in both groups. The RF group improved from 19 to 21.9 and the PFME group improved from 17.9 to 19.6, although no statistical significance was reached between the groups. Dyspareunia, assessed by the Marinoff scale, improved only after RF therapy [9] . This paper described a participant in the microablative RF group who had mild vaginal burning with spontaneous improvement and mild dyspareunia after three months.

The studies that compared non-ablative RF, monopolar or bipolar, there were no records of side effects or secondary infections [8] [9] [10] .

In a systematic review, other authors observed a 50.6% reduction in vaginal symptoms, a 72.1% reduction in sexual complaints sustained for two months after treatment [1] .