The present study showed that laparoscopic cystectomy for endometrioma caused a more significant damage to the ovarian reserve compared with that for ovarian mature teratoma. These findings are consistent with recent studies . In addition, this study showed that the damage to the ovarian reserve after cystectomy in patients with mature teratoma is positively correlated with cyst size (especially for cysts > 5.13 cm), whereas cyst size in patients with endometrioma showed no correlation with damage to the ovarian reserve after surgery.
Although laparoscopy is the first–line management for benign ovarian cysts, controversy exists regarding the most appropriate time for surgical intervention that could minimize ovarian damage. These cysts are common in younger women; thus, identifying the appropriate time of surgery is crucial for sparing residual functioning ovarian tissue after surgery.
The European Society of Human Reproduction and Embryology guidelines recommend that surgery should be performed in women complaining of endometriosis-associated pain or in women with endometrioma (≥ 3 cm) . However, a number of studies reported that cystectomy for endometrioma may be harmful for the ovarian tissue [16, 17], and some recent studies showed reduction in ovarian reserve after surgery based on serum AMH levels.1 Moreover, removal of endometriomas before in vitro fertilization did not improve fertility outcomes , and post-cystectomy ovaries showed reduced follicular response in natural and clomiphene citrate cycles . However, substantial evidence on expectant versus surgical management of endometrioma is lacking. Few recent studies on the influence of cyst size on ovarian reserve after cystectomy have been conducted. Chen et al. reported that operation-related damage to the ovarian reserve is positively related to bilateral endometriomas and endometrioma > 7 cm . Mehdizadeh Kashi et al. demonstrated that laparoscopic cystectomy, particularly endometriomas with bilateral involvement and those at least 5 cm in diameter, is associated with post-operative decrease in serum AMH level . Exacoustos et al. showed that ovarian stripping of endometriomas, but not of ovarian mature teratomas, is associated with a significant decrease in residual ovarian volume, which could result in diminished ovarian reserve and function .
Several reasons for the decrease in ovarian reserve after cystectomy have been proposed. First, cystectomy using the stripping technique could result in inadvertent removal of a healthy ovarian tissue and decreased ovarian reserve [13, 22]. The second possible reason is the ovarian vascular injury associated with bipolar electrocoagulation . Nevertheless, the mechanisms underlying the decrease in ovarian reserve after cystectomy remain unknown. In addition, the aforementioned reasons were mainly from studies of patients with endometrioma. Thus, whether laparoscopic cystectomy for nonendometriotic ovarian cyst could decrease ovarian reserve remains to be established.
In this study, the postoperative decrease in AMH level in patients with endometrioma showed no correlation with cyst size, age, BMI, locularity of cyst, and preoperative AMH level. Although the size of mature teratoma was positively related to the rate of decrease in the AMH level, it was not correlated with age, BMI, locularity of cyst, and preoperative AMH level. These results indicate that laparoscopic cystectomy for a relatively large mature teratoma could result in significant damage to the ovarian reserve.
In our opinion, the finding that ovarian reserve after cystectomy decreases supports the second reason mentioned previously; i.e., vascular injury during surgery plays a role. The amount of ovarian normal tissue removed during stripping of mature teratoma could be less than that during stripping of endometrioma because mature teratomas, unlike endometriomas, can be enucleated more easily. In this study, further analysis was performed to explore the association between the cyst diameter and the rate of decrease in AMH level after cystectomy. The ROC curve analysis revealed that a larger cyst diameter was associated with increased damage to the ovarian reserve. In the subgroup with a cyst diameter > 5.13 cm, a statistically significant decrease in the ovarian reserve was found. This result could be because the hilum of the ovary opens up and more vessels of the mesovarium are exposed as the diameter of the cyst increases. Thus, hemostasis should be implemented more extensively following stripping of cysts with larger diameters. Moreover, some studies about the effects of different hemostatic methods on ovarian reserve showed that bipolar electrocoagulation hemostasis applied to laparoscopic cystectomy is associated with a significant reduction in ovarian reserve compared with the suture hemostasis technique [23, 24] Zhang et al. also showed that recovery of ovarian reserve was greater in patients with suture hemostasis than in those with bipolar electrocoagulation and ultrasonic scalpel , and they emphasized the importance of protecting the ovarian blood supply system to maintain ovarian function. In our study, damage to the ovarian reserve after surgery was more severe in patient with mature teratomas with cysts > 5.13 cm, suggesting that sugery on cysts with larger diameters could result in exposure of extensive vessels. Furthermore, controversies regarding the best surgical intervention to manage mature teratomas exist given that these cysts are extremely common among reproductive-aged women and they also grow very slowly, i.e., by 1.7–1.8 mm each year . Kim et al. reported no difference in preoperative serum AMH level between women with mature teratoma and age- and BMI-matched controls . Legendre et al. recommended that a wait-and–see attitude appears reasonable for asymptomatic women, especially for moderate-sized mature teratomas (4–6 cm), where the risk of secondary interventions is low . However, our results showed that laparoscopic cystectomy is associated with severe damage to the ovarian reserve, particularly with cysts > 5.13 cm. Therefore, a surgical approach instead of expectant management should be considered in young patients with a relatively large mature teratoma to minimize the risk of damage to ovarian reserve due to cystectomy.
In endometrioma cases, several other possible reasons for a decrease in ovarian reserve, such as the inadvertent removal of healthy ovarian tissue during cystectomy or vascular compromise, have been proposed, including excessive adhesiolysis  and postsurgical inflammation [28, 29]. Muzii et al. reported that the ovarian tissue adjacent to the endometrioma wall differs morphologically from the normal ovarian tissue and is possibly nonfunctional, thereby suggesting that ovarian function disruption may have already been present before laparoscopic excision . Hence, factors other than cyst size seems to contribute to the decreased ovarian function after cystectomy in patients with endometrioma.
This study has some limitations. The number of patients was small, and the study had a retrospective design. In addition, only serum AMH levels measured 1 month after surgery were used to assess the risk of postoperative damage to ovarian reserve. Nonetheless, our study has several strengths. The same skilled operator performed each surgery, which removed the influence of surgical skill on surgical outcomes. Additionally, CT or MRI was used to accurately measure the diameter of the ovarian cyst. Only patients with unilateral ovarian cysts were included in the investigation of the relationship between cyst size and postoperative ovarian damage.