Different types of abdominal wall endometriosis have different clinical features and surgical outcomes

Of 122 patients, there were 28 cases of type I (23.0%), 55 cases of type II (45.1%), and 39 cases of type III (31.9%). All patients had confirmed endometriotic nodules at the abdominal wall by pathology. 121 cases (99.2%) had a history of cesarean section, and only 1 case (0.8%) had a history of other gynecologic operations. Baseline characteristics of the patients are summarized in Table  1 . Table 1 Clinical and operative characteristics at different groups I ( N  = 28) II ( N  = 55) III ( N  = 39) P Age(years) 34(23–43) 34(27–45) 34(25–48) 0.4851 Latency period(years) 3.67 ± 2.94 3.75 ± 2.53 4.17 ± 2.43 0.6784 3(1–15) 3(0–9) 4(0.5–13) Size(cm) 1.9(0.9–3.2) 2.0(0.7–5.9) 2.9(0.5–8.3) *< 0.0001 1.92 ± 0.73 2.25 ± 0.85 3.13 ± 1.47 Multiple lesions (No) 1(3.6%) 6(10.9%) 6(15.4%) 0.3018 MRI (No) 3(10.7%) 7(12.7%) 7(17.9%) 0.6594 Operative time(min) 44.03 ± 25. 89 56.04 ± 30.32 103.46 ± 60.30 *< 0.0001 40(20–140) 50(20–180) 90(30–300) Blood loss(ml) 8.25 ± 6.42 12.13 ± 12.98 32.31 ± 62.90 *0.0127 5(1–20) 5(1–50) 20(5–400) Hospital stays(days) 6.28 ± 1.86 7.04 ± 2.87 8.79 ± 4.13 *0.0042 6(3–11) 7(2–16) 8(3–19) Clinical and operative characteristics at different groups 107 patients (87.7%) presented a symptom of abdominal wall masses and 107 patients (87.7%) suffered from abdominal wall pain associated with menstruation. Periodic/Cyclic abdominal pain occurred in 21 cases of type I patients (75%), 51 cases of type II (92.7%), and 35 cases of type III (89.7%), and there was no significant different among three types ( P  = 0.06). All patients received abdominal wall ultrasonography and 17 patients received magnetic resonance imaging (MRI), and only 1 patient received computer tomography (CT) to measure the lesions before surgery. The rate of multiple lesions in type II and type III was higher than that in type I (10.9%, 15.4% vs. 3.6%). And the maximal ultrasonographic diameters increased with the location of lesions deepen (type I, 1.9 ± 0.7 cm; type II, 2.3 ± 0.9 cm; and type III, 3.1 ± 1.5 cm), the differences were statistically significant ( P  < 0.0001). The operative time for the various types of patients, the deeper the level of lesion invasion, the longer the operative time, and the results between the groups were all statistically different ( P  < 0.0001). 8 cases of pelvic endometriosis were found during the operation-accounting for 8.5% of the total cases of type II and III patients with pelvic endometriosis. 6 patients with type III AWE required primary mesh repair, representing 15.4% of the 39 women with type III, and the difference of the rate of mesh repair in different types was statistically significant ( P  = 0.0012). Patients who had larger resection area and all the patients who had patch placement underwent drainage on the layer of fascia (Table  2 ). Table 2 Clinical signs and postoperative symptoms at different groups I ( N  = 28) II ( N  = 55) III ( N  = 39) P Dysmenorrhea + 10(35.7%) 17(30.9%) 22(56.4%) *< 0.0001 - 18 38 17 Abdominal wall mass + 27(96.4%) 47(85.5%) 33(84.6%) 0.2753 - 1 8 6 Cyclic pain + 21(75%) 51(92.7%) 35(89.7%) 0.0600 - 7 4 4 Bleeding + 6(21.4%) 11(20%) 9(23.1%) 0.9520 - 22 43 30 Pelvic endometriosis + 0(0%) 4(7.2%) 4(10.3%) 0.2367 - 28 51 35 Mesh + 0 0 6(15.4%) *0.0012 - 28 55 33 Drainage + 1(3.6%) 3(5.5%) 11(28.2%) *0.0012 - 27 52 28 Fever + 1(3.6%) 2(3.6%) 6(15.4%) 0.0679 - 27 53 33 Recurrence + 1(3.6%) 1(1.8%) 0 0.5197 - 27 54 39 Clinical signs and postoperative symptoms at different groups The patient’s hospital stays, postoperative fever, and drainage were analyzed in groups, and the results are shown in Table  2 . With the deepening of the endometriotic invasion, the proportion of patients with postoperative fever gradually increased ( P  = 0.0679), and the length of hospital stay was significantly prolonged ( P  = 0.0042). All patients were pressure bandaged after the operation, the incisions healed at grade A, and the wounds healed satisfactorily at the time of discharge. The patients were followed up for 21–156 months, with an average follow-up time of 91.16 ± 39.88 months and a median follow-up time of 93 months. We followed 105 cases, and 2 cases were diagnosed as AWE recurrence, including 1 case in type I and 1 case in type II. Rates were not statistically significant from one another.

This retrospective, observational, descriptive study included a cohort of 122 women who underwent surgery at our institution from January 2011 to January 2023, and who had a confirmed diagnosis of AWE upon histopathology (Fig.  1 ). We reviewed each patient’s history, characteristics, clinical presentation, nodule size and location, concomitant pelvic endometriosis, and recurrence. Fig. 1 Flow chart of the study Flow chart of the study This study protocol was approved by the Institutional Review Board (IRB) of Beijing Chao-Yang Hospital affiliated to Capital Medical University (IRB no. 2025-science-24). This committee deemed that participant consent was not required due to the retrospective nature of the study. For patients with initial onset, the latency period refers to the time from the previous cesarean section or gynecologic operation to the appearance of a mass on the abdominal wall; for patients with recurrence, the incubation period refers to the time after the last resection of the abdominal wall endometriotic lesion to the reappearance of the mass. Except for two consecutive measurements on the day of the operation (with an interval of ≥ 4 h between the two measurements), patients with a temperature ≥ 38.5 °C were defined as exhibiting postoperative fever. According to the position of the endometriotic mass, patients were divided into three types (Fig.  2 ). Type I included AWE with infringement of the skin and adipose layer; type II reflected mass infringement of the fascial rectus abdominis, which can invade the skin and subcutaneous tissue at the same time; and type III showed infringement of the muscle and/or peritoneum, which can also invade the skin and subcutaneous tissue simultaneously. If the mass invaded multiple layers, it was classified according to the deepest level of its invasion. Fig. 2 Three types were divided according to the position of the endometriotic mass Three types were divided according to the position of the endometriotic mass All of the patients were followed up for 2–10 years. Given the long duration of follow-up, the observation ended up after the patients experienced spontaneous menopause. During the follow-up period, telephone or outpatient follow-up was conducted. A painful mass on the abdominal wall found on physical or imaging examination was defined as a clinical recurrence. Statistical analysis was performed using SPSS 25.0 (SPSS Inc., Chicago, IL, USA). The normality of continuous variables was tested using the Shapiro–Wilk test, and comparisons of normally distributed, continuous data were made with Student’s t-test. Three sets of non-normally distributed, continuous data were analyzed with the rank-sum test; otherwise, we employed the Kruskal–Wallis H test. The categorical data were analyzed with χ2 and the Fisher exact probability test. The differences were considered statistically significant when the P value was less than 0.05.

Our data showed that the different layers invaded by the AWE lesions have different clinical characteristics and have an impact on surgical results, but no impact on the chance of recurrence. Our report reminds us that all types of the AWE have the risk of multiple lesions. It suggests that evaluating the lesion pre-operatively help to make a complement plan for treatment. Considering the diagnosis of AWE, the clinical triangle includes cyclical pain, a lump at or near the level of the scar/abdominal wall and a history of caesarean section or similar gynecological procedures [ 4 , 5 ]. Type III AWE carries more severe clinical manifestations, larger lesion size, longer operative time, higher necessity of mesh implantation, and longer postoperative recovery process. Ultrasound remains the best screening method [ 6 ]. MRI is better used in cases with small lesions, and is the most commonly used method for evaluating pelvic endometriosis and also used for preoperative disease staging, while CT provides better results in cases with muscle and subcutaneous layer involvement [ 6 – 8 ]. Generally, the screening tool remains ultrasound and as a next step MRI or CT is useful [ 7 ]. Sumathy et al. [ 9 ] reported concurrent endometriosis in 18.9% of cases, and recently, Leng et al. [ 2 ] found that during the operation, 26.6% of the type III patients with pelvic endometriosis, while others reported no synchronous pelvic lesions [ 10 ]. The recurrence rate of AWE has previously demonstrated to be 4.3–11.4%. It also found that most of the recurrence sites were located in the fascia and rectus abdominis. Recurrence may also be due to a deeper location [ 3 ], accompanied by satellite lesions that were not visible to the naked eye, resulting in incomplete removal. Study in which comparisons were made between different types of AWE was limited [ 2 , 11 ]. Leng et al. demonstrated that the 5-year cumulative recurrence rate for type I, II and III was 4%, 3.3%, and 4.3%, respectively [ 2 ]. And Pei XT et al. found that the recurrence rate of type I, II and III was 10.0%、6.9%、5.0%, respectively [ 11 ]. Rates were not statistically significant from one another. The recurrency of AWE is low and complete resection of the lesion is critical for preventing recurrent. Minimally invasive techniques, including high-intensity focused ultrasound (HIFU) ablation, percutaneous image-guided cryoablation [ 12 ], and ultrasound-guided microwave ablation, and thermal ablation has also been reported to treat AWE. For a large and deeply invading lesion, noninvasive treatment including HIFU has been widely used to treat AWE [ 13 , 14 ], in which has less trauma and fewer complications, but similar results, compared with surgery [ 15 ]. Ultrasound-guided microwave ablation is characterized by high ablation temperatures, large ablation volumes, fast ablation times, and the ability to use multiple applicators simultaneously and can be proposed in outpatients. And it also has been reported to the treatment of AWE [ 16 ]. Surgical resection remains the standard of care in the management of AWE. The major limitations of the present analysis were acknowledged: the retrospective nature of the clinical data and the long period of the collected data, and consequently it is less easy to contact and convoke them for postoperative visits. However, only 13.9% of women were lost to follow-up. Another limitation is that the surgeries were performed by different surgeons. And our study only mentioned the clinical features of abdominal wall endometriosis treated by surgery.

In conclusion, considering the different layers invaded by the lesions have an impact on surgical results, it suggests that evaluating the lesion pre-operatively help to make a complement plan for treatment. Maybe, it is the time to think that the approach should be varied based on its relationship to the fascia. However, the large number of patients and the long follow-up period enhance the validity of the study. The mechanisms responsible for its development and its pain should be further understood in future [ 3 , 17 ].

Abdominal wall endometriosis (AWE) is defined as the implantation and embedding of ectopic endometrial tissue into the abdominal wall [ 1 ]. The majority of AWE is secondary to the incision of cesarean section, and it could also be secondary to other gynecologic operations [ 1 ], and can invade all layers of the abdominal wall. However, It remains unclear whether the layer invaded by the lesion have an impact on surgical methods, surgical results, or the likelihood of recurrence [ 2 , 3 ]. We reviewed 122 cases of AWE managed at the Beijing Chaoyang Hospital over a 12-year period and also the current literature. In this study, we aimed to assess the differences in demographic and clinical characteristics, surgical options, recurrence rates, and association with pelvic endometriosis in various types of patients with AWE.