Ultrasound and single‐port laparoscopic‐guided microwave ablation of abdominal wall endometriosis lesions: A single‐center observational study

Abstract

Introduction

Raising the temperature of abdominal wall endometriosis lesions contributes to an effective ablation; however, providing sufficient protection to the surrounding tissues remains a challenge. In this study, we aimed to combine ultrasound and single‐port laparoscopic images to not only achieve complete ablation of abdominal wall endometriosis lesions but also protect surrounding tissues from damage. The adverse events and complications were Common Terminology Criteria for Adverse Events grade 1 or Society of Interventional Radiology classification grade A.

Material and Methods

This historical study included 30 patients with abdominal wall endometriosis who underwent ultrasound and single‐port laparoscopic‐guided microwave ablation at the Ultrasonography and Gynecology Department of the Wuhan Central Hospital between October 2017 and February 2022. Ultrasonography and magnetic resonance imaging were used to evaluate the number, size, and depth of the lesions. Pain levels were assessed using a visual analog scale. Subsequently, ultrasound and single‐port laparoscopic‐guided microwave ablation of the lesions was performed, and patients were followed up to monitor the lesion volume and pain.

Results

One patient experienced an intra‐abdominal wall burn that was detected by single‐port laparoscopy, and ablation was stopped immediately. No other complications were recorded. Following surgery, the lesion volume decreased and was lower than the preoperative lesion volume at 1 year postoperatively (1.6 ± 1.3 vs. 4.0 ± 3.6 cm³; p < 0.05). Visual analog scale scores revealed that, compared with preoperative levels, pain was reduced significantly at all postoperative time points (p < 0.01). The recurrence rate was 16.7% (5/30).

Conclusions

The addition of single‐port laparoscopy to ultrasound‐guided microwave ablation may allow greater protection of the surrounding tissues, particularly in cases involving deep lesions, and may, therefore, represent a promising clinical treatment strategy.

Ultrasound‐guided percutaneous microwave ablation of abdominal wall endometriosis is safe and effective, and it is safer when combined with single‐port laparoscopy monitoring in the case of deep lesions.

Abbreviations

AWE

abdominal wall endometriosis

HIFU

high‐intensity focused ultrasound

Key message.

Additional monitoring during microwave ablation of abdominal wall endometriosis lesions, with single‐port laparoscopy and ultrasonography, may provide extra protection for unaffected tissues, particularly those surrounding deep lesions, consequently increasing the clinical applicability of this technique.

1. INTRODUCTION

Endometriosis is characterized by the growth of tissue similar to that found in endometrial glands and stroma outside of the uterine cavity. Abdominal wall endometriosis (AWE), which has an incidence of 0.03%–5%, ¹ , ² , ³ typically occurs secondary to surgical procedures such as cesarean section, hysterectomy, or salpingostomy or following amniocentesis. The main manifestations of AWE are cyclic abdominal pain and a palpable mass, ³ which affects the quality of life and mental health of patients, while the malignant transformation rate is 1%. ⁴

Current treatment methods for AWE include medication, surgical resection, and high‐intensity focused ultrasound. The effectiveness of drug therapy for AWE remains unclear, and the long‐term use of these drugs can cause adverse effects. ³ , ⁵ , ⁶ Accordingly, surgical excision remains the standard treatment for symptomatic AWE, with recommended surgical margins of at least 1 cm to ensure complete disease resection. Nevertheless, mesh introduced to support the abdominal wall structure increases the risk of infection, ³ , ⁵ and reoperation may be required in cases of disease recurrence. ² High‐intensity focused ultrasound (HIFU) ablation is a novel non‐invasive treatment strategy with proven safety and efficacy. However, protecting the surrounding tissue, including the bowel, while achieving complete ablation remains a challenge.

In the present study, we used microwave ablation to treat AWE. This technology uses a microwave radiator to convert electromagnetic wave energy into microwave radiation energy, which is absorbed by tissue and converted into heat energy, causing tissue coagulation and necrosis. Microwave ablation is another form of thermal ablation with shorter ablation, operation, and anesthesia times than HIFU. ⁷ , ⁸ HIFU ablation destroys the AWE lesion; however, inaccurate positioning of the HIFU ablation wand during treatment may result in skin burns. Accordingly, we aimed to combine ultrasound and single‐port laparoscopic monitoring to not only achieve complete ablation but also protect surrounding tissues from damage. In single‐port laparoscopy, the abdominal wall is separated from important organs such as the intestinal tube, and a sufficient safe distance is maintained. At the same time, the lens is pointed at the abdominal wall, and the color change of the abdominal wall, whether there is bleeding in the abdominal wall, and whether there is adhesion in the abdominal wall during ablation were observed. This real‐time, dual‐monitoring approach leads to fewer surgical complications and is especially suitable for deep endometriosis lesions.

2. MATERIAL AND METHODS

2.1. Study design and population

Patients with AWE who underwent ultrasound‐guided microwave ablation at Wuhan Central Hospital between October 2017 and February 2022 were included in this retrospective study. Patients were followed up using a combination of in‐person appointments and telephone calls. The abdominal wall lesion depth was classified as follows: type I (superficial implant/above the muscle fascia), type II (intermediate/at the level of the rectus muscle fascia), and type III (deep position/below the fascia). Patients with type I lesions were included in the surface group, whereas those with type II or III lesions were included in the deep group.

The inclusion criteria for undergoing ultrasound‐guided microwave ablation were as follows: (1) women of reproductive age with AWE lesions following uterine surgery, (2) abdominal pain related to the menstrual cycle, and (3) size and location of AWE lesions confirmed by ultrasound. The exclusion criteria were as follows: (1) pregnancy or lactation and (2) skin inflammation or ulceration near the AWE lesion.

2.2. Examination and treatment

Ultrasonography was performed using a Philips IU22 color Doppler ultrasound machine with a superficial probe (Philips). Biopsies were obtained using a Bard MC1810 puncture needle (BD). Microwaves were generated using an ECO‐100 cold circulation dual‐source microwave tumor therapeutic apparatus (Nanjing Yigao Microwave System Engineering Co., Ltd.) with water circulation cooling, a frequency of 2450 MHz, output power of 40–80 W, and an AL8/AL3 ablation needle. Laparoscopy was performed using a single port (Kangji Medical).

Following admission to the hospital, data on the following baseline patient characteristics were collected: age, body mass index, lesion size, lesion quantity, number of previous cesarean sections, latency (the intermediate time between the last C‐section and the formation of the abdominal mass), relative locations of lesions and scars, symptoms, any other deep lesions, and visual analog scale pain scores. In the absence of contraindications for surgery, ultrasound‐guided puncture biopsy of AWE lesions was performed, followed by microwave ablation. The power level was set at 50 W to achieve complete ablation of endometriosis lesions. The ablation was complete when the ablation of strong echo completely covered the lesion area and margin. The total ablation time was recorded, as were any intraoperative complications. Postoperative pathological examinations were performed to confirm the diagnosis of endometriosis.

2.3. Follow‐up

All patients were followed up until August 2023 at 1, 3, and 6 months and at 1, 2, 3, 4, and 5 years postoperatively by telephone or in person. The visual analog scale was used by patients to report pain levels, with 0, 1–3, 4–6, and 7–10 points representing no, mild, moderate, and severe pain, respectively. If the patient could not come to the hospital for follow‐up because of various reasons, we conducted a telephone follow‐up, during which the numerical rating scale (NRS) was used. At follow up, lesion volume (d1 × d2 × d3 × π/6), visual analog scale pain scores, and recurrence were assessed.

Symptom relief was defined as the substantial relief of cyclic abdominal pain or absence of a palpable mass. Recurrence was defined as abdominal wall pain returning to preoperative levels or the presence of an abdominal wall mass on physical examination after 3 months of symptom relief.

2.4. Statistical analyses

Data are presented as the mean ± standard deviation for normally distributed data or as the median ± quartile for non‐normally distributed data. For the measurement data of multiple samples, one‐way analysis of variance was used for the comparison of normally distributed data, and the least significant difference test was used for pairwise comparison; the Kruskal–Wallis test was used to compare non‐normally distributed data. For the count data of two independent samples and multiple samples, the chi‐squared test or continuity correction analysis was used for comparison. The Fisher exact test was used for four 2 × 2 contingency tables. SPSS software (version 27.0; IBM Corp.) was used to perform statistical analysis, and a p‐value < 0.05 was considered statistically significant.

3. RESULTS

3.1. Lesion location

Lesions were classified as type I (superficial) or type II or type III (deep) according to their depth, which was determined using ultrasonography combined with magnetic resonance imaging. Representative images of superficial and deep lesions are shown in Figure 1.

FIGURE 1.

Lesions classified according to depth. (A) Ultrasonography and (B) magnetic resonance imaging of a superficial lesion. Ultrasonography shows that the hypoechoic lesion was in the superficial layer of the myofascial layer, mostly in the fat layer, with a lack of clear boundaries and an uneven internal echo. Magnetic resonance imaging shows a short T1 long T2 signal shadow under the subcutaneous lower abdominal wall, with a range of approximately 10 × 12 × 9 mm; the inner edge is closely connected with the rectus abdominis. (C) Ultrasonography and (D) magnetic resonance imaging of a deep lesion. Ultrasonography shows that the hypoechoic lesion was in the muscular layer, with a lack of clear boundaries and an uneven internal echo. Magnetic resonance imaging shows a short T1 and slightly long T2 signal shadow in the right lower rectus abdominis, with uneven and mixed signals, a range of 13 × 22 × 29 mm, and an unclear edge. Endometriosis with bleeding was considered.

3.2. Baseline patient characteristics according to lesion depth

Of the 30 patients with AWE and complete follow‐up data included in this study, 18 (60%, 18/30) had type I, 10 (33.3%, 10/30) had type II, and two (6.7%, 2/30) had type III lesions. The superficial and deep groups included 18 and 12 patients, respectively.

There were no significant differences between the superficial and deep groups in terms of age, body mass index, lesion size, previous cesarean sections, latency, relative locations of the lesions and cesarean scars, preoperative presence of mass and pain, or duration of pain (all, p > 0.05). Almost all patients (96.7%, 29/30) experienced preoperative cyclic abdominal pain, including 24 with menstrual pain, one with ovulatory pain, and four with pain around the time of menstruation.

All 30 patients had a history of cesarean section. One patient (3.3%, 1/30) had undergone hysteroscopic cervical polypectomy, two patients (6.67%, 2/30) had undergone laparoscopic myomectomy, and one patient (3.3%, 1/30) had undergone two laparoscopic myomectomies (Table 1).

TABLE 1.

Baseline patient characteristics according to lesion depth.

Characteristic	Surface group (n = 18)	Deep group (n = 12)	p‐Value
Age, years	35.5 ± 5.1	34.3 ± 4.6	0.50
Body mass index, kg/m2	25.8 ± 1.6	25.5 ± 1.5	0.62
Lesion size, cm3	3.00 ± 0.63	5.60 ± 1.23	<0.05
Lesion number
One	18 (100%)	12 (100%)
Multiple	0 (0%)	0 (0%)
Number of cesarean sections			0.18
One	16 (88.9%)	8 (66.7%)
Two	2 (11.1%)	4 (33.3%)
Latency, years	7.0 ± 4.1	4.2 ± 3.0	0.05
Relationship with scar location			0.14
Left side	12 (66.7%)	4 (33.3%)
Right side	6 (33.3%)	8 (66.7%)
Presence of palpable mass
Yes	18 (100%)	12 (100%)
No	0	0
Cyclic abdominal pain
Yes	17 (94.4%)	12 (100%)
No	1 (5.6%)	0
Duration of pain, days	7.2 ± 2.5	8.6 ± 1.9	0.12
Presence of other deep lesion	0	0

Note: Surface group: the depth of lesion invasion is above the muscle fascia; deep group: the depth of lesion invasion is at the level of the rectus muscle fascia or below the fascia. Data are expressed as mean ± standard deviation or number (percentage).

Of the 30 cases included this study, only one patient developed abdominal wall endometriosis after cesarean section and experienced recurrence after surgical removal of the heterotopic lesion. This patient experienced postoperative recurrence and underwent two abdominal wall operations, cesarean section, and abdominal wall adenomyoma extraction. None of the other patients (29/30) received any other treatment previously.

3.3. Imaging changes and intraoperative complications during ablation

Figure 2 shows changes in ultrasonograms captured during ablation, with the low echo of the lesion slowly becoming obscured by the high echo of the thermal radiation area. The single‐port laparoscopy used to monitor the abdominal wall (Figure 3A) revealed few intraoperative complications during ablation. One patient experienced burning of the abdominal wall (Figure 3B), causing the ablation needle to be immediately withdrawn. Subsequently, edema and abdominal wall thickening were observed in this patient (Figure 3C). No other intraoperative complications, including skin pain, skin burning, bleeding, infection, or poor wound healing, were observed.

FIGURE 2.

Changes in two‐dimensional gray‐scale ultrasound images during ablation. (A) Before ablation, the abdominal wall lesion can be seen as an unencapsulated low echo area with a clear boundary, irregular shape, and uneven internal echo. Further images recorded after (B) 20, (C) 60, and (D) 120 s of ablation show high echo in the thermal radiation area during ablation. Over time, the high echo range gradually expanded to cover the lesion.

FIGURE 3.

Burning of the abdominal wall during ablation. (A) Preoperative laparoscopic image of the abdominal wall. (B) Burning of the abdominal wall causes the tissue to become yellow, as indicated by the green arrows. (C) Postoperative laparoscopic image of the burned abdominal wall shows edema and thickening, as indicated by the blue arrows.

3.4. Follow‐up

Compared with the preoperative lesion volume (4.0 ± 3.6 cm³), the lesion volume at 1 year postoperatively was significantly lower (1.6 ± 1.3 cm³; p < 0.05). No further significant differences were observed between the other time points (Table 2). Compared with the preoperative pain score (6.4 ± 1.1 points), the postoperative pain scores were significantly lower at all time points (p < 0.01) (Table 2).

TABLE 2.

Lesion volume and pain scores during the follow‐up period.

Parameter	Before treatment	Months after treatment (follow up)
		1 (30)	3 (30)	6 (30)	12 (30)	24 (28)	36 (24)	48 (21)	60 (17)
Lesion volume (cm3)	4.0 ± 3.6	2.6 ± 1.9	2.2 ± 1.5	1.9 ± 1.3	1.6 ± 1.3 a	1.9 ± 1.2	1.8 ± 1.4	2.1 ± 1.1	1.5 ± 1.1
Visual analog scale	6.4 ± 1.1	1.5 ± 1.2 b	1.4 ± 1.0 b	1.3 ± 1.0 b	1.2 ± 1.0 b	1.5 ± 1.5 b	1.3 ± 1.5 b	1.1 ± 1.6 b	0.7 ± 1.4 b

^a p < 0.05.

^b p < 0.01 vs. before treatment. Data are expressed as mean ± standard deviation.

Three patients (10%, 3/30) experienced disease recurrence in the first postoperative year, one patient experienced recurrence in the second postoperative year (13.3%, 4/30), and one patient experienced recurrence in the third postoperative year (16.7%, 5/30); no further cases of recurrence were observed in the fourth and fifth postoperative years. Accordingly, the total recurrence rate was 16.7% (5/30). Two of the patients who experienced recurrence had a history of pelvic surgery: one had undergone laparoscopic myomectomy, and the other had undergone two laparoscopic myomectomies. Table S1.

4. DISCUSSION

Symptomatic AWE can result in long‐term adverse effects on the quality of life and work productivity and can result in massive increases in healthcare costs. Therefore, it is crucial to diagnose and treat it at an early stage. At present, the therapeutic methods for AWE include medical management, surgical excision, and minimally invasive techniques. The success rate of medical therapy has been reported to be low, and a temporary alleviation of symptoms following the use of oral contraceptives, progestogens, danazol, progesterone, and aromatase inhibitors is often followed by recurrence after cessation of the drug. ² , ⁹ Traditionally, surgical excision has been the primary treatment for AWE. To prevent recurrence, appropriately expanding the scope of surgical resection, such as by a margin of 1 cm, is considered adequate. However, expanding the scope of surgical resection for AWE patients with involvement of the abdominal wall fascia and muscle may lead to complex repairs, including the need for flaps and mesh by Cocco et al. ¹⁰ , ¹¹ The reduction in lesion volume and pain after microwave ablation were consistent with the conclusions of Liu et al.'s study, ¹² which was a retrospective study of nine women with pathologically proven endometriosis of the abdominal wall. In this study, after microwave ablation treatment, the volume of all nodules significantly decreased and no major complications were observed. All patients had subjective improvement in their cyclical abdominal wall pain. The most common site of extraperitoneal endometrial tissue growth is the abdominal wall outside the site of previous pelvic surgeries. Owing to the estrogen and progesterone dependence of AWE, edema or even hemorrhage is thought to occur during cyclic changes in estrogen and progesterone levels, as in the normal endometrium; outside the uterine cavity, this induces fibrosis or adhesion of surrounding tissues and eventually leads to the formation of local nodular lesions. Therefore, patients with AWE experience estrogen and progesterone cycle‐related pain, which seriously affects their health and quality of life. Malignant transformation has been reported in approximately 1% of endometriosis cases. ⁴

Microwave ablation technology has previously been applied to liver tumors, thyroid tumors, endometriosis, and AWE. ¹³ , ¹⁴ , ¹⁵ , ¹⁶ , ¹⁷ The present study's results demonstrated that the lesion volume decreased significantly after 1 postoperative year. Prior to this time point, tissue edema may have contributed to lesion volume. Wang et al. ¹⁸ reported that HIFU ablation of AWE resulted in a significantly lower lesion volume at 6 months postoperatively compared with preoperative values, as determined by contrast‐enhanced ultrasonography. The difference in volume assessment methods may explain the earlier lesion volume decrease observed in this study compared to the present study. However, in the present study, visual analog scale scores showed a significant decrease in pain levels at all postoperative time points compared with preoperative levels, showing that the treatment had achieved its aim; the results are consistent with those of studies by Wang et al. and Yang. ¹⁸ , ¹⁹ Recurrence manifested in 16.7% of patients. Compared with other treatments, the overall success of medical management is temporary, with symptom recurrence following drug discontinuation reported by Allen et al. ² , ²⁰ The recurrence risk ranges from 4.3% to 11%, but the risk can be minimized by ensuring adequate margins during surgery. ¹ , ²¹ We hypothesize that the recurrence rate will be increased by laparoscopic myomectomy. When the uterine fibroids are located in or near the endometrium, the fibroids are removed laparoscopically. In this case, endometriosis may be placed intramuscularly or ectopic into the subcutaneous soft tissue layer, and this may cause endometriosis of the abdominal wall. As the number of cases in our center continues to increase, we will further study the issue of relapse factors. We also assessed lesions according to depth, with different depths requiring different treatment methods; superficial lesions can be treated with ultrasound‐guided percutaneous ablation, but deep lesions require a single‐port laparoscopy to allow observation. Although this distinction has been made previously, it was not in the context of microwave ablation. ²² Single‐port laparoscopy is performed through the patient's umbilicus after the establishment of the artificial pneumoperitoneum, expanding the subcutaneous space and making the operating space clearer, while also facilitating the monitoring and heating of deep lesions during ablation. Therefore, single‐port laparoscopy and ultrasound‐guided ablation of AWE lesions is beneficial if the lesion is deep—located in or below the rectus abdominis—and invades the posterior and posterior sheath of the rectus abdominis. Accordingly, the surgical procedure requires laparoscopy to optimally observe color changes. Alternatively, if the patient is obese and the lesion is close to the abdominal wall and surface, single‐port laparoscopy can help avoid thermal damage to the viscera under artificial pneumoperitoneum, and the abdominal and pelvic wall can be observed under laparoscopy for the presence of visceral and peritoneal adhesion, avoiding damage to important blood vessels, nerves, and visceral organs. Ablation can be stopped immediately in cases of abdominal wall thermal damage and discoloration to protect the abdominal wall and surrounding tissues from further damage.

Several certain limitations should be considered in our study. It was a single‐center retrospective observational study with a small number of cases. Additionally, according to the location of the lesions, the patients were divided into the surface or deep group, and the number of patients in each group was small. Thus, a comparative study between the two groups was not possible. The promising findings reported herein warrant confirmation in further large‐cohort prospective studies. In subsequent studies, we plan to conduct further research on ablation precision treatment to reduce unnecessary damage to surrounding tissue, while also combining a variety of treatments to reduce recurrence.

5. CONCLUSION

Ultrasound and single‐port laparoscopy‐guided ablation of AWE was associated with significant decreases in lesion volume and pain, with few adverse effects recorded. The recurrence rate in this study was 16.7%, indicating its potential as an important clinical treatment method. With the continuous application and development of ultrasound‐guided minimally invasive technology, clinicians are seeking to minimize surgical trauma while retaining satisfactory treatment effects.

AUTHOR CONTRIBUTIONS

All authors contributed to the study design, data collection, writing of the manuscript, data cleaning, statistical analysis, research guidance, and manuscript editing. Shunshi Yang: Conceptualization, methodology, project administration, resources, software, supervision, validation, and writing—review and editing. Jueying Li: Conceptualization, data curation, formal analysis, methodology, supervision, validation, and writing—original draft. Jingjing Li: Data curation, formal analysis, funding acquisition, project administration, and writing—original draft. Xiaoyu Zhao: Investigation, methodology, software, and supervision. Mengying Li: Data curation and project administration. Yi Zhang: Data curation, project administration, and supervision. Xiong Li: Conceptualization, resources, and writing—review and editing. Ying Chen: Investigation, resources, and validation.

FUNDING INFORMATION

This work was supported by a grant from the Wuhan Municipal Health Commission of Hubei Province, China (grant number: WX21C36).

CONFLICT OF INTEREST STATEMENT

The authors declare no conflicts of interest.

ETHICS STATEMENT

This study was approved by the Ethics Committee of the Wuhan Central Hospital on October 8, 2015 (Wuhan Health and Family Planning Commission Application [2016] 17); all patients provided informed consent.

Supporting information

Table S1.

Yang S, Li J, Li J, et al. Ultrasound and single‐port laparoscopic‐guided microwave ablation of abdominal wall endometriosis lesions: A single‐center observational study. Acta Obstet Gynecol Scand. 2025;104:755‐762. doi: 10.1111/aogs.15051

DATA AVAILABILITY STATEMENT

Data are available from the corresponding authors with the permission of the Central Hospital of Wuhan.