Current Endometriosis Classifications (rASRM, #Enzian, AAGL2021) and their Correlation with Operative Time

Abstract

Introduction

In the ongoing effort to identify or develop the optimal classification system for endometriosis, there is a paucity of data regarding the association between currently used classification systems and operative times. This study aims to evaluate the correlation between the rASRM, #Enzian, and AAGL2021 classifications and the duration of endometriosis surgery to determine the most accurate system for planning operating room resources.

Materials and Methods

This retrospective study included patients who underwent laparoscopic endometriosis surgery at Kepler University Hospital in 2021 and 2022. Surgeries were performed by experienced gynecologic surgeons, with endometriosis extent assessed using rASRM, #Enzian, and AAGL2021 classifications. Corrected operative time (total time minus fixed durations for common concomitant procedures) was used for analysis. Statistical analyses included descriptive statistics, Kendall’s tau correlation, Spearman’s correlation, Mann-Whitney U test, and generalized linear models.

Results

Out of 248 patients with laparoscopic surgery for endometriosis, 139 met the in-/exclusion criteria. The median corrected operative time was 68.50 minutes. Significant positive correlations were found between surgery duration and stages in both rASRM and AAGL2021 classifications. The #Enzian classification also showed positive correlations with more complex analyses attributable to the classification structure. Operative times were longest in surgeries affecting compartments C3, A3, FI, and FU. Regression analysis identified several significant variables impacting surgery duration.

Conclusions

All three classification systems significantly impact operative time, with higher stages or specific coding correlating with longer durations. The AAGL2021 and #Enzian classifications can be used as preoperative diagnostic tools, with #Enzian offering more detailed coding. Future research should focus on prospective, multi-center studies to develop algorithms incorporating #Enzian codings for enhanced preoperative planning.

Zusammenfassung

Einleitung

Bei den laufenden Bemühungen, die optimale Klassifikation für Endometriose zu identifizieren oder zu entwickeln, gibt es aktuell nur wenige Daten zum Zusammenhang zwischen derzeit existierenden Klassifikationssystemen und der Dauer von Endometriose-Operationen. Ziel dieser Studie war es, die Korrelation zwischen den rASRM-/#Enzian-/AAGL2021-Klassifikationen und der Operationsdauer zu evaluieren, um das geeignetste System für die Planung von OP-Ressourcen zu ermitteln.

Material und Methodik

In diese retrospektive Studie wurden alle Patientinnen eingeschlossen, die sich 2021 oder 2022 am Kepler Universitätsklinikum einer laparoskopischen Endometriose-Operation unterzogen haben. Die Operationen wurden von erfahrenen gynäkologischen Chirurgen durchgeführt, die das Ausmaß der Endometriose anhand der Klassifikationen rASRM, #Enzian und AAGL2021 beurteilten. Für die Analyse wurden korrigierte Operationszeiten (Gesamtzeit minus festgelegter Dauer für häufige Begleiteingriffe) verwendet. Die statistischen Analysen umfassten deskriptive Statistik, Kendall-Tau-Korrelation, Spearman-Korrelation, Mann-Whitney-U-Test und verallgemeinerte lineare Modelle.

Ergebnisse

139 von insgesamt 248 Patientinnen mit laparoskopischer Endometriose-Operation erfüllten die Ein- und Ausschlusskriterien. Die mediane korrigierte Operationszeit betrug 68,50 Minuten. Es zeigten sich signifikant positive Korrelationen zwischen der Operationsdauer und den rASRM- wie auch den AAGL2021-Stadien. Auch die #Enzian-Klassifikation zeigte positive Korrelationen, bei jedoch komplexeren Analysen aufgrund der Klassifikationsstruktur. Die längsten Operationszeiten traten bei Beteiligung der Kompartimente C3, A3, FI und FU auf. Eine durchgeführte Regressionsanalyse identifizierte mehrere signifikante Variablen, die sich auf die Operationsdauer auswirkten.

Schlussfolgerungen

Alle 3 Klassifikationssysteme zeigen signifikante Korrelationen zur Operationszeit, wobei höhere Stadien oder spezifische Kodierungen mit einer längeren OP-Dauer assoziiert sind. Die AAGL2021- und #Enzian-Klassifikationen können präoperativ eingesetzt werden, wobei #Enzian eine detailliertere Kodierung bietet. Zukünftig sollten Algorithmen zur Planung von OP-Zeiten unter Einbezug von #Enzian-Kodierungen entwickelt und in prospektiven, multizentrischen Studien getestet werden.

Keywords

endometriosis - surgery time - #Enzian - AAGL2021 - rASRM

Schlüsselwörter

Endometriose - Operationsdauer - #Enzian - AAGL2021 - rASRM

Introduction

Endometriosis is a chronic gynecological disease that affects approximately 10% of women of reproductive age. It is defined as the presence of endometrial tissue outside the uterus, which may manifest as peritoneal lesions, ovarian cysts (known as endometriomas), or deep endometriosis [1] [2] [3].

Commonly used classification systems for endometriosis are the rASRM, the #Enzian, and the AAGL2021 classification. The rASRM score is the most widely used classification system, but hardly describes deep endometriosis [4] [5]. The #Enzian classification describes superficial and deep endometriosis, as well as ovarian endometriosis, adhesions and adenomyosis [6]. The AAGL2021 classification is a 4-stage system analogous to the rASRM classification but has been developed to better reflect surgical complexity of endometriosis surgery by using a more detailed mapping [7].

The treatment options for endometriosis vary depending on the symptomatology and results of non-invasive diagnostics, with surgery being one of the primary treatment pillars, along with hormonal treatment. Preoperative planning plays a critical role in optimizing health resource management, particularly in the context of endometriosis surgery, where operative times can vary significantly based on disease extent and complexity. Optimal estimation of the planned surgery duration can achieve improved operating room efficiency, more accurate scheduling, reduced patient waiting times and better resource allocation [8]. To the best of our knowledge, no publication has evaluated the duration of endometriosis surgery in relation to the stage of all three classification systems mentioned above within the same patient cohort.

The aim of this study was to evaluate the correlation between the rASRM, #Enzian, and AAGL2021 classifications and the duration of surgery. The main intention was to ascertain which of these classifications most accurately reflects the duration of surgery and should be employed to plan operating room resources.

Material and Methods

Participants in this retrospective data analysis were all patients who underwent laparoscopic endometriosis surgery at the Department of Gynecology, Obstetrics and Gynecological Endocrinology at the Kepler University Hospital in 2021 and 2022. Eligible patients were identified using the digital surgery book of the hospital information system. The following exclusion criteria were formulated: lack of histological evidence of endometriosis, incomplete treatment of endometriosis, as well as additional surgical indications besides endometriosis with an influence on the duration of surgery (e.g., simultaneous hysterectomy, ovarian cysts of a different entity). However, for some frequently performed additional surgical procedures (e.g., hysteroscopy), a time factor was added to enable inclusion in the study (see [Table 1] below). These specific correction time factors are based on evaluations of procedure duration in the operating room and have been rounded up to five-minute thresholds. The time factors were subtracted from the total operative time resulting in a corrected operative time that was then used for further calculations.

Table 1 Time factors for additional intraoperative measures.

Additional intraoperative measures	Frequency [n]	Time factor [min]
min = minutes
Hysteroscopy + chromopertubation	10	10
Hysteroscopy + curettage + thermal balloon endometrial ablation	1	20
Conization	2	10
Prophylactic salpingectomy	4	5
Hysteroscopy	3	10

All surgeries were performed by gynecologic surgeons with substantial experience in endometriosis treatment; when necessary, in multidisciplinary collaboration (e.g., colorectal surgeon). The extent of endometriosis was assessed intraoperatively using the rASRM, #Enzian and AAGL2021 classifications. However, the AAGL2021 score was only applied intraoperatively to patients from November 2021 onwards regarding to its publication date. For patients operated before November 2021, the AAGL2021 score was assigned retrospectively based on the surgical report and stored intraoperative images. This partially retrospective staging of the AAGL2021 classification was performed or supervised by the last author (S-H.E.).

The study was approved by the Institutional Ethics Committee of the Johannes Kepler University (submission number 1188/2022, date of first approval 08/10/2021).

Statistical analysis

Descriptive statistics, including frequencies, means, medians, interquartile ranges (IQR) and standard deviations, were calculated to summarize the data. Kendall’s tau correlation was used to determine if there was a correlation between the operative time and the rASRM/AAGL2021 classifications. Two tests were used to calculate the correlation between the #Enzian compartments and operative time: Spearman’s correlation and the Mann-Whitney U test (for the F compartments). Generalized linear models for regression analysis were performed to explore whether there were significant associations between the individual compartments of the #Enzian classification and the duration of surgery.

The level of significance was set to p < 0.05, and no adjustment for multiple testing was used. Data were analysed using SPSS Statistics 29.0.2.0.

Results

Origin and description of dataset

248 patients underwent laparoscopic surgery for endometriosis at the Department of Gynecology, Obstetrics, and Endocrinology at the Kepler University Hospital (KUK) between 2021 and 2022. After applying the exclusion criteria, 139 patients were included in the study – 64 in 2021 and 75 in 2022. The flowchart of the inclusion process is shown in [Fig. 1].

Fig. 1 Flowchart of inclusion process.

The median age in the dataset is 32 years (IQR = 28–37) with a median BMI of 22.86 kg/m² (IQR = 20.31–25.71). Of the patients included, 50.4% had undergone at least one previous abdominal surgery, and eight patients had undergone three or more abdominal surgeries. The most prevalent subtype of endometriosis in the sample was peritoneal endometriosis (85.6%), followed by ovarian endometriosis (49.6%), deep endometriosis (46.8%), and adenomyosis (22.3%). Rectal involvement was observed in 10.1% of patients. According to the AAGL2021 classification, 43.2% of patients were classified as stage 1, 30.9% as stage 2, 5.0% as stage 3 and 20.9% as stage 4, while according to the rASRM classification, 37.5% of study participants were in rASRM stage 1, 12.5% in stage 2, 36.8% in stage 3 and 13.2% in stage 4. The distribution of affected compartments according to the #Enzian classification is provided in the appendix (Table S1 online).

The median “actual” operative time – after subtracting time factors for additional intraoperative measures – was 68.50 minutes (IQR = 46.75–97), with a minimum of 19 minutes and a maximum of 402 minutes. In two cases rectal shaving was required, eight patients had an intestinal resection without stoma and one patient had an intestinal resection with stoma. In one case, the surgical procedure was converted from laparoscopic surgery to laparotomy.

AAGL2021 and rASRM in relation to surgery time

As illustrated in [Table 2], a comparison has been made of the operative times of the rASRM and AAGL2021 classifications across different stages. The median operative time increased with stage in both the rASRM classification and the AAGL2021 classification. Using Kendall’s tau correlation, a significant positive correlation (p < 0.001) has been identified between the stages and the duration of surgery in both classifications.

Table 2 Operative times for the different stages of the rASRM and AAGL2021 classifications.

	rASRM classification					AAGL2021 classification
Stage	n	min	max	Median (IQR)	Kendall’s tau correlation	n	min	max	Median (IQR)	Kendall’s tau correlation
Operative times in minutes IQR = interquartile range; max = maximum; min = minimum
I	51	19	156	47 (34–63)	ρ = 0.465 p < 0.001	60	19	156	47 (35.25–63.75)	ρ = 0.572 p < 0.001
II	17	34	287	68 (58.5–78)		43	25	189	72 (54–90)
III	49	25	351	79 (55–124.5)		7	62	290	79 (64–145)
IV	17	45	402	110 (97–232.5)		28	69	402	124 (97.75–221.25)

#Enzian classification in relation to surgery time

Due to the more complex structure and the lack of stages, the evaluation of the #Enzian classification is more complex. [Table 3] shows the descriptive statistics for operative time in relation to the compartments of the #Enzian classification. The longest median operative time can be found for surgeries coded C3. Also, A3 and the involvement of compartments FI and FU showed long median operative times. Spearman’s correlation for individual compartments of the #Enzian classification shows significant positive correlations (p < 0.001) between surgery duration and all compartments. A regression analysis was carried out to identify associations between the #Enzian compartments and the operative time as a whole (Table S2 online). Several parameters are statistically significant, including O2right, C3, C1, FA, and FU, indicating these factors have a significant impact on the operative time in the dataset.

Table 3 Operative times for the different compartments of the #Enzian classification.

	#ENZIAN classification
	0	pos	1	2	3	Correlation/ p value
Data as Median [IQR] in minutes, IQR = interquartile range “pos” refers to all positive parts of the compartment (1–3 of the corresponding compartment) Correlation: Spearman Correlation for P/O/T/A/B/C compartments and Mann-Whitney U test for F compartments * significant in the regression analysis (details in Table S2) ** Upper quartile could not be calculated due to small sample size.
Comp P	71.5 [49.75–101.5]	68 [46–96.25]	51 [39–77.25]	75 [63.35–124.5]	122.5 [85.5–168]	ρ = 0.283 p < 0.001
Comp O left	58.5 [42.5–78.75]	88 [63.75–123.75]	96 [66–116.5]	80 [47–127]	89.5 [67–125.25]	ρ = 0.312 p < 0.001
Comp O right	58 [41–83]	81 [63–122.5]	75 [50.5–119.5]	94.5 [70.75–125.75]*	86 [67.25–117.25]	ρ = 0.355 p < 0.001
Comp T left	55 [41.75–74.25]	97 [77.25–134.5]	92 [70.5–116]	128.5 [58.5–169.5]	103 [84–255]	ρ = 0.482 p < 0.001
Comp T right	59.5 [44–86.25]	104 [84.5–232.5]	104 [77–209]	90 [90–90]	104 [84.5–232.5]	ρ = 0.410 p < 0.001
Comp A	60 [41–80]	103.5 [67–143.25]	68.5 [52.75–126.25]	117 [85.5–130]	287 [103–351]	ρ = 0.434 p < 0.001
Comp B left	58.5 [39–78]	86.5 [58–131.5]	67.5 [49.25–83]	103 [78–255]	156 [129–225]	ρ = 0.439 p < 0.001
Comp B right	59.5 [41–86.25]	97 [64–139]	80 [58–124]	107 [67.75–213.75]	131 [123–NA]**	ρ = 0.351 p < 0.001
Comp C	62.5 [44.25–86.75]	162 [122–322.75]	144 [86.25–178.5]*	116 [104–NA]**	324.5 [203.5–363.75]*	ρ = 0.444 p < 0.001
Comp FA	59.5 [43.5–89]	97 [68–225]*	NA	NA	NA	p < 0.001
Comp FB	68.5 [46.25–96.75]	160 [65–NA]**	NA	NA	NA	p = 0.328
Comp FI	67.5 [46–95]	222 [124.5–365.25]	NA	NA	NA	p < 0,001
Comp FU	68 [46–96]	255 [79–NA]*, **	NA	NA	NA	p = 0.028

Discussion

This study represents a pioneering effort to compare operative times for endometriosis surgery according to codings by the #Enzian, rASRM and AAGL2021 classifications. The findings indicate a significant correlation between extended endometriosis and the length of surgical procedures in all three classifications, whether by stages in the rASRM and AAGL2021 classifications or by compartments in the #Enzian classification.

For both four-stage classification systems (rASRM and AAGL2021), the median operative time extended with increasing stages. In the existing literature, there is a lack of explicit studies investigating operative times according to rASRM stage. An indirect correlation was observed in a study by Nicolaus et al. reporting that higher rASRM stages are associated with more complications, leading to longer operative times [9]. However, the rASRM classification does not adequately capture deep endometriosis, which may be a contributing factor why this system alone does not fully reflect the actual surgical effort for more complex cases [10]. Furthermore, the applicability of the rASRM classification in a preoperative non-invasive setting is limited, thereby restricting its use for preoperative planning of operating room resources.

Similar to rASRM, there is a shortage of studies reporting surgical duration according to the AAGL2021 stage. A comprehensive search of the PubMed database failed to identify any publications that addressed operating times in relation to the AAGL2021 classification. Even in the original publication on the AAGL2021 classification, no operating times are presented in the surgical validation cohort [7]. However, a study by Abrao et al. on the applicability of ultrasound concluded that patients can be reliably identified preoperatively with the correct AAGL2021 stage [11]. This statement, in conjunction with the presents study’s results, underscores the potential for incorporating AAGL2021 staging into preoperative planning tools.

The #Enzian classification, with its detailed coding of endometriosis by affected compartments and size, revealed a more complex relationship with the duration of surgery. Specifically, the compartments C, FI, and FU were associated with the longest median operative times, highlighting the significant impact of deep endometriosis on surgical complexity and duration, particularly in cases of bowel involvement. This finding is in line with the study of Haas et al., in which a multiple regression analysis for predicting operating time based on the Enzian classification showed an extension of the operation time when C3 is involved [12]. Another study by Thomassin-Naggara et al., based on preoperative Enzian codings by MRI, demonstrated that the operating time for Enzian coding C3 was significantly longer than for C2 [13]. In both studies an earlier version of the Enzian classification was used, but its basic structure has been retained in the current #Enzian classification. The regression analysis of the #Enzian compartments in our study further identified compartment O (ovarian endometriomas) and FA (adenomyosis) as relevant influencers on surgery duration. A study of Banerjee et al. described that the presence of endometriomas is a good indicator for the presence of rectosigmoid disease and involvement of the posterior cul-de-sac [14]. Other studies have demonstrated a strong association between adenomyosis and deep endometriosis [15] [16]. Whether adenomyosis plays an independent role or is merely a surrogate marker of accompanying deep endometriosis cannot be determined by the study’s data.

The #Enzian classification can be applied either intraoperatively or by using imaging modalities such as ultrasound or MRI. By precisely mapping endometriosis across anatomical compartments and lesion sizes, the #Enzian demonstrates strong potential as a predictive tool for surgical complexity and duration, particularly through its associations with deep infiltrating compartments like C, FI, and FU, as well as ovarian involvement and adenomyosis. In contrast to rASRM, the AAGL2021 and #Enzian classifications offer preoperative utility, with #Enzian particularly suited for algorithmic tools due to its structured and compartmental format. However, high-quality preoperative mapping and use of detailed classification systems requires in-depth anatomical knowledge and targeted training to ensure consistent and correct use. Systems like #Enzian or AAGL2021 should be regarded as a crucial quality standard to promote continuous improvement in preoperative planning.

Recent studies have reported alternative scores for predicting the length of surgery. For instance, the preoperative applicability of the NMS-E (Numerical Multi-Scoring System of Endometriosis) was described in a recent paper [17]. This score demonstrated a robust correlation with the rASRM score and surgical outcomes, and was useful in predicting surgical duration. The Deep Pelvic Endometriosis Index magnetic resonance imaging score (dPEI score) is a newly published preoperative score for women with deep endometriosis based on MRI images. This score is helpful in predicting operating time, length of hospitalisation and postoperative complications [18]. Ebrahimi et al. evaluated a preoperative five-domain ultrasound-based endometriosis staging system (UBESS), which was compared postoperatively with the RANZCOG/AGES system. The results showed that preoperative ultrasound using the UBESS staging system was able to predict the complexity of laparoscopic surgery [19]. The list demonstrates that new endometriosis classifications are springing up, yet a universally accepted classification remains elusive. Fadinger et al. described in their study a first attempt to convert the #Enzian classification into a 4-stage scoring system comparable to the AAGL classification, demonstrating an overlapping of both classification systems. In their opinion, there should be a universal classification in the future that incorporates the strengths of existing classifications [20].

The strength of the study lies in its direct comparison of three distinct endometriosis classifications within a single data set of a diverse endometriosis population. Consistent surgical procedures by physicians at an endometriosis center certified by EuroEndoCert ensure high standards of care and expertise [21]. However, limitations of the study must be acknowledged including its retrospective study design and single-center data collection. Experience in endometriosis surgery and individual surgical technique plays an important role in the duration of surgery, making it challenging to extrapolate the time data to other centers. Additionally, a larger study population would facilitate a more nuanced analysis of the complex #Enzian coding system, maybe enabling a preoperative planning tool. While certain compartments in the #Enzian classification (e.g., C3, FI, FU) showed statistically significant associations with prolonged operative time in the regression analysis, these findings must be interpreted with caution due to the small sample sizes in those subgroups, increasing the risk of overfitting or type I error. However, it is important to emphasize that the statistically significant findings in our study align well with clinical experience and plausibility. The time factors employed for minor additional intraoperative interventions may introduce inaccuracies in the actual operative time, though this is presumed to have no substantial impact on the study’s findings.

Conclusion

All three classification systems used in our study (#Enzian, AAGL2021 and rASRM) show a considerable impact on operative time, with an increase in duration corresponding to higher stage or specific coding. This underscores the importance of non-invasive classification systems as predictors of surgical complexity and duration. In contrast to the rASRM classification, the AAGL2021 and #Enzian classifications can be used as preoperative diagnostic tools, with the #Enzian offering a more diverse coding. Future research should focus on prospective studies with larger, multi-center datasets to develop algorithms incorporating codings from the #Enzian classification for enhanced preoperative planning. Such advancements could lead to more accurate predictions of surgery duration and better resource allocation.

Appendix – Supporting Information

• Table S1: Distribution of the compartments of the #Enzian classification.

• Table S2: Results of the Regression Analysis for the compartments of the #Enzian classification.

Conflict of Interest

The authors declare that they have no conflict of interest.

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Publication History

Received: 25 April 2025

Accepted after revision: 30 August 2025

Article published online:
25 September 2025