Background
The current laparoscopic procedures for ovarian endometriomas, which affects 17 %–44 % of women with endometriosis [
1], include ovarian cystectomy, ablation of the cyst wall and fenestration of cysts [
2]. According to the European Society of Human Reproduction and Embryology (ESHRE) guidelines, ovarian cystectomy is preferred for the secondary prevention of endometriosis-associated symptoms and for increasing the spontaneous pregnancy rate [
3]. However, both the guidelines and previous studies suggested a possible post-surgical reduction in the ovarian reserve, which indicates that follicles are inadvertently removed by the stripping of the cyst wall [
4‐
7]. The serum concentration of anti-Müllerian hormone (AMH) is a highly sensitive marker of ovarian reserve, and, owing to its stability, it can be used to evaluate ovarian reserve after surgery to treat ovarian endometriomas [
8,
9]. Serum AMH concentrations are known to significantly decrease after cystectomy for ovarian endometriomas.
The ESHRE working group established the Bologna criteria in 2011, which proposed a definition for the term poor ovarian responder (POR) to controlled ovarian stimulation for assisted reproductive technology (ART) [
10]. A recent study reported that, based on the Bologna criteria, women diagnosed with POR after cystectomy for ovarian endometriomas had significantly lower clinical pregnancy and live birth rates after in vitro fertilisation (IVF) than women who were idiopathic PORs [
11]. The study suggested that some patients with ovarian endometriomas have a potential risk of diminished ovarian reserve (DOR) and becoming a POR following ovarian cystectomy. However, the potential incidence and the risk factors have not yet been adequately investigated.
The aims of the present study were to investigate the factors associated with DOR and the potential risk of becoming a POR before and after laparoscopic cystectomy of ovarian endometriomas, and to evaluate the feasibility of pre-surgical prediction of post-surgical DOR according to the Bologna criteria.
Methods
Patients and recruitment
Patients who were admitted to our hospital from January 2009 to May 2015 for symptomatic ovarian endometrioma with a cyst >4 cm in diameter were enrolled in the present study. The disorder was diagnosed using transvaginal ultrasound and pelvic magnetic resonance imaging. The inclusion criteria were as follows: 1) non-pregnant patients; 2) age under 45 years with a regular menstrual cycle; 3) absence of any leiomyoma involving the cavity or intramural leiomyoma >3 cm in diameter; 4) absence of any other bleeding diseases; 5) absence of endocrine disorders, including thyroid dysfunction, hyperprolactinemia and Cushing’s syndrome; 6) no previous history of abdominal surgery; 7) absence of malignant ovarian diseases and 8) no previous history of hormonal treatment within 3 months before blood collection. The diameters of the ovarian cysts were measured in all the patients by ultrasound before surgery.
Definitions of pre-and post-surgical adverse DOR
In accordance with the Bologna criteria, AMH concentrations already decreased to <1.1 ng/mL before surgery were defined as pre-surgical adverse DOR (aDOR) with a potential risk of the patient becoming a POR. AMH concentrations that were >1.1 ng/mL before surgery but decreased to <1.1 ng/mL at 3 or 6 months after laparoscopic cystectomy were defined as post-surgical aDOR. None of the patients underwent postoperative hormonal therapy until 6 months after surgery.
Measurements
The diameters of the ovarian cysts were measured in all patients using ultrasound before surgery; the concentrations of serum AMH, luteinising hormone (LH), follicle-stimulating hormone (FSH), estradiol and cancer antigen 125 (CA125) were also measured. In patients with bilateral ovarian endometriomas, the total diameter was calculated as the sum of the diameters of both cysts. Serum AMH concentrations were also measured at 3 and 6 months after surgery. The sera, obtained from the blood samples by centrifugation (1,400 × g, 10 min) to separate the cellular contents and debris, were transferred into sterile polypropylene tubes and then cryopreserved at −80 °C until analysis. The serum AMH concentrations were measured using an enzyme immunoassay kit according to the manufacturer’s instructions (EIA AMH/MIS; Immunotech, Marseille, France). The intra- and inter-assay coefficients of variation for the AMH assay were below 12.3 and 14.2 %, respectively.
Surgical procedures
All surgical procedures were performed by the same skilled surgeon (J.K.). The patient was placed in a 30° reverse Trendelenburg lithotomy position under general anaesthesia, and endotracheal intubation was then performed, with a pneumoperitoneum created using CO
2 insufflation with an umbilical 11-mm trocar (VersaStep™; Covidien, Mansfield, MA, USA), approached via the closed method and maintained at a pressure of 10 mmHg. Under observation using a 10-mm rigid laparoscope (Endoeye™; Olympus, Tokyo, Japan) inserted through the umbilical trocar, three additional sites for trocar (VersaStep™; Covidien) insertion were made as follows: two 5-mm sites at 2 cm above the anterior superior iliac spine and a 12-mm site on the left side of the umbilicus on the left axillary line. A uterine manipulator (Ethicon, Somerville, NJ, USA) was inserted in the uterus of the patient, and the severity of pelvic endometriosis was assessed using a scoring system according to the revised American Society of Reproductive Medicine (Re-ASRM) classification immediately before initiating the laparoscopic procedures [
12]. Furthermore, patients underwent adhesiolysis of the obliterated cul-de-sac when necessary. After the cyst was aspirated and drained, adhesions between the cyst wall and the pelvic wall or bowel were lysed, and an 18-gauge infusion needle was used to inject diluted vasopressin (Pitressin®; Goldshield Pharmaceuticals, Croydon, Surrey, UK; 0.1 U/mL: 10 U diluted with 100 mL saline) from the inner surface of the cyst wall into the subcapsular space depending on the diameter of the incised ovarian cyst. The incision was further extended to strip the cyst wall from the surrounding normal ovarian cortex as gently as possible using two atraumatic grasping forceps for traction and counter-traction after identifying the cleavage plane. After completion of the excision of the cyst capsule, 3–0 absorbable sutures (PolySorb®; Covidien) were used for approximation of the ovarian edges and bleeding control. Electrocoagulation with a monopolar (30-W) needle knife for haemostasis was minimally used before approximation. The total duration of the surgery was calculated as the sum of the amounts of elapsed time between the skin incision and the start of the pneumoperitoneum, the intra- and extracorporeal manipulations and the skin closure after finishing the pneumoperitoneum.
Statistical analyses
Statistical analyses were performed using the computer software package IBM SPSS Statistics version 20 (IBM, Armonk, NY, USA). A Kolmogorov–Smirnov test was performed to analyse the normality of the respective parameters. Unpaired Student’s t-tests or the Mann–Whitney U-test was performed to compare consecutive variables, and chi-square tests or Fisher’s exact test was performed to compare categorical variables. The results are expressed as the mean ± standard deviation and 95 % confidence interval (CI) or median and range. Attribution analysis of the factors influencing pre- and post-surgical aDOR was followed by forward stepwise variable selection; logistic regression analysis was performed to minimise the effects of confounding factors. Receiver operating characteristic (ROC) curves were used to obtain the area under the curve (AUC) as well as the sensitivity and specificity for the predictive value of pre-operative AMH. The highest Youden index (sensitivity + specificity - 1) was considered as the optimal cut-off point for outcome prediction. A p value of <0.05 was considered statistically significant. Among the patients, the cumulative spontaneous pregnancy rate of infertile patients was analysed using the Kaplan–Meier method. Patients who were lost to follow-up or who underwent ART during the observation period until 6 months after surgery were defined as censored data. The cumulative pregnancy rates between the groups were compared using the log-rank test. We also calculated odds ratios (ORs).
Discussion
The results of the present study demonstrate that age and pre-surgical serum FSH concentrations were significantly associated with pre-surgical aDOR and that pre-surgical serum AMH concentrations and bilateral cystectomy were significant factors influencing the likelihood of a patient having post-surgical aDOR at 3 and 6 months after surgery. The optimal cut-off points of the pre-surgical AMH concentration to predict post-surgical aDOR due to ovarian cystectomy by ROC curve analysis were also determined. In addition, the cumulative spontaneous pregnancy rate was significantly lower in the post-surgical aDOR group than in the non-aDOR group at 6 months after surgery.
As evaluated by serum AMH concentrations, the reduction of ovarian reserve after ovarian cystectomy for endometriomas is inevitable. In our study population, 21.7 % of the patients were classified in the pre-surgical aDOR group based on the Bologna criteria. A decline in serum AMH concentration is highly correlated with the increasing age in women [
13,
14]. Our data suggested that the ovarian reserve of aged patients with ovarian endometriomas was already diminished before surgery; thus, it is presumed that serum AMH concentrations in patients who have intrinsically low AMH concentrations would be further diminished. Therefore, the assessment of pre-surgical ovarian reserve for predicting further post-surgical decline of ovarian reserve could be more reliable if the serum AMH concentrations would be assessed in combination with a patient’s age and serum FSH concentration, which is a conventional ovarian reserve marker.
Several previous studies demonstrated that bilateral ovarian cystectomy is a significant factor associated with the decline of serum AMH concentrations after cystectomy for ovarian endometriomas [
15‐
17]. The results of the present study revealed that pre-surgical AMH concentration is a crucial factor for the decline in serum AMH concentrations after unilateral and bilateral ovarian cystectomy. We believe that the post-surgical ovarian reserve after ovarian cystectomy for endometriomas depends on the pre-surgical potential of the ovarian reserve. In addition, it is thought that the optimal cut-off points of the pre-surgical serum AMH concentrations determined in the present study will be valuable for the pre-surgical prediction of DOR leading to patients becoming PORs. Previous studies have reported that the serum AMH concentrations in most patients who underwent a cystectomy for ovarian endometriomas decreased immediately after surgery and that the concentrations in some patients continuously decreased after the immediate reduction [
18,
19]. The authors of these previous studies hypothesised that the continuous decline of the AMH concentrations could be attributed to vascular compromise, although the mechanisms are unknown. Our results showed that the cut-off point of the pre-surgical AMH concentrations in patients who underwent bilateral ovarian cystectomy at 6 months after surgery was increased compared with that at 3 months after surgery and that these cut-off points were higher at both 3 and 6 months compared with the concentrations of those who underwent unilateral ovarian cystectomy. We believe that these declines in the post-surgical serum AMH concentrations of patients who underwent bilateral cystectomy were due to a lower rate of recovery or a continuous decrease in AMH concentration because of the extended ovarian ischemia resulting from the bilateral surgery.
Meticulous surgical techniques for the excision of the capsule of ovarian endometrioma to find a correct cleavage plane and to achieve adequate haemostasis by coagulations using an energy devise are important for preserving the ovarian reserve [
20]. In addition, an alternative management to cystectomy for ovarian endometriomas may be better for patients in whom further decline of the ovarian reserve should be prevented. Less reduction in serum AMH concentrations and antral follicle count (AFC) was observed when vaporising internal cyst walls using a CO
2 laser as the source of energy compared with the excision of the cyst wall because the CO
2 laser could vaporize only the filmy superficial internal lining up to 1.0 to 1.5 mm of the cyst wall [
21]. However, higher recurrence rate after the vaporization remains debatable. Donnez et al. [
22] reported that the ovarian volume and AFC did not significantly different between the operated ovary by combining excision and vaporization using CO2 laser and the contralateral unaffected ovary, with a low recurrence rate at short-term follow-up. In contrast, for patients who already have a decreased ovarian reserve before surgery and who desire pregnancy, ART may be more suitable because it has been reported that IVF outcomes, including oocyte retrieval and pregnancy, are promising even though the responsiveness of ovarian hyperstimulation may be decreased owing to the presence of the ovarian endometriomas [
23]. Therefore, further research is required to examine whether these alternative managements instead of cystectomy are feasible for avoiding the impairment of future fertility in the predicted post-surgical DOR patients who have a potential risk for being post-surgical PORs.
The results of the present study demonstrated that the cumulative spontaneous pregnancy rate was significantly lower in the post-surgical aDOR group at 6 months after surgery than in the post-surgical non-aDOR group; the rate at 18 months after the 6-month post-surgical measurements of serum AMH concentrations was approximately 60 % in the post-surgical non-aDOR group. Although the Bologna criteria define PORs with respect to ART outcomes, our data indicate that post-surgical DOR based on the criteria are reflected in the spontaneous pregnancy rate after cystectomy of ovarian endometriomas; this rate might not have been as low if the patients had not become PORs post-surgically. Vercellini et al. reported that the spontaneous pregnancy rate after ovarian cystectomy for endometriomas in infertile patients ranged from 30 % to 67 %, and they concluded that the pregnancy rate 12 months after surgery in patients who underwent surgery for ovarian endometriomas could be hypothetically estimated to be not greater than 25 % owing to the multiple confounding factors of the studies in this field, including selection and publication bias [
24]. Although the actual spontaneous pregnancy rate after ovarian cystectomy for endometriomas is debatable, the variability of this rate in previous studies might be related to the heterogeneity of the patients who experience difficulty getting pregnant owing to the degree of DOR in each study.
One limitation of our study is that we did not examine other markers of ovarian reserve. AFC is significantly correlated with serum AMH concentrations and is a reliable marker of the ovarian reserve [
25]; however, the correlation was slightly altered when compared between operated and contralateral healthy ovary after cystectomy for unilateral ovarian endometrioma. Ercan et al. [
23] demonstrated that AFC of the operated ovary significantly decreased compared with that of the non-operated ovary, although serum AMH concentrations did not significantly change at 3 months after laparoscopic unilateral cystectomy. Furthermore, meta-analysis for ovarian reserve after excisional surgery demonstrated that the ovarian reserve of the operated ovary, evaluated using AFC, was not significantly reduced after surgery, although AFC of the operated ovary after surgery was lower than that of the non-operated ovary [
26]. Moreover, they stated that AFC is more accurate as a marker for ovarian reserve than AMH concentration because AFC directly indicates the ovarian reserve expressed by each single ovary. Conversely, AMH expresses the ovarian reserve of both ovaries, where a balancing effect of a healthy ovary may compensate for a reduced ovarian reserve in the contralateral affected ovary. Furthermore, the AMH values do not represent the quality of the oocytes. As the Bologna criteria define POR with respect to patient age, which is an oocyte quality-related factor, and to the responsiveness to ovarian stimulation, the outcomes of ART for these DOR patients may differ depending on the definitions used. Therefore, it is thought that other markers of ovarian reserve should also be evaluated to assess the reproducibility of our data.
Acknowledgement
There was no acknowledgement.