CSE is an uncommon iatrogenic disease caused by endometrium implantation in the incision during cesarean delivery. In the present study, we investigate 198 cases of CSE over a period of 13 years, providing detailed information that helps us to better understand the clinical characteristics of this rare condition.
Several theories about the pathogenesis of AWE have been proposed, such as the implantation theory, the coelomic metaplasia theory, and the lymphatic or hematogenic dissemination theory [8, 19]. As the most common type of AWE, CSE is best explained by the iatrogenic direct implantation theory. During cesarean delivery, endometrial tissue is seeded into the wound. With an appropriate supply of nutrients and hormonal stimuli, these endometrial cells survive and proliferate, finally leading to CSE. In the present study, most of the endometriomas were located in a corner of the incision scar: 83.0% in Pfannenstiel incision scars and 84.2% in vertical midline incision scars. In another large retrospective study, conducted by Yan Ding et al., similar results were obtained [20]. In their study, 77.1% of the endometriomas were located in the corners of the scars. This is probably because endometrial cells are less easily removed from the corners of the incisions during CS. Thus, our data also support the iatrogenic cell implantation theory. However, the implantation theory alone cannot completely explain the pathogenesis of CSE, given the low incidence of CSE. Residual endometrial cell contamination of the wound during CS occurs often and sometimes is inevitable, but CSE is rare. Hereditary predisposition may confer susceptibility to the development of CSE [21].
CS is one of the most common surgical procedures performed on women worldwide. Pfannenstiel incision and vertical midline incision are the two most frequently used abdominal skin incisions. The vertical midline incision has the advantages of speed of abdominal entry and less bleeding, but has a higher risk of incisional hernia and results in a less cosmetically pleasing scar. Conversely, the Pfannenstiel incision has a lower risk of incisional hernia and results in a better cosmetic appeal. However, the Pfannenstiel incision usually involves more dissections, and the blood loss following dissection may be greater [22].
CSE is a complication of cesarean surgery. Unfortunately, the relationship between the CS incision type and the pathogenesis of CSE is still unknown. The Pfannenstiel incision is the most commonly reported type for the occurrence of CSE; however, because of the disease rarity and the need for the pathological confirmation of the diagnosis, it is difficult to estimate the population-wide incidence of CSE for different incision types [19, 20]. Demiral et al. speculated that Pfannenstiel incisions confer a higher risk of CSE than do midline incisions, but without sufficient evidence [23]. In this study, the latency period of CSE was 31.6 ± 23.9 months, which was comparable with that reported in other studies [19, 24]. However, when comparing the latency period of CSE in patients with Pfannenstiel incisions to those with vertical midline incisions, we observed a significantly shorter latency in Pfannenstiel incisions (24.0 vs 33.0 months, P = 0.006) (Table 3). In other words, CSE in patients with Pfannenstiel incisions occurred earlier than in patients with vertical incisions. This indicates that, compared to the vertical incision, the Pfannenstiel incision might be more favorable to the implantation and proliferation of the residual endometrial cells. We suggest two possible causes for the favorable role of the Pfannenstiel incision. First, the Pfannenstiel incision involves wider dissection planes and more gaps, rendering tissue irrigation difficult and inducing much more endometrial cell contamination [22]. The second cause is a larger nutrient supply. Due to the longitudinal pattern of the abdominal vessels and the large dissection, more capillaries are cut off during a Pfannenstiel incision than in a vertical incision, causing more blood loss. Endometrial cells require an adequate blood supply to survive in their ectopic sites, and angiogenesis plays an important role in the pathogenesis of endometriosis [25]. Therefore, more blood loss in the Pfannenstiel incision would provide a relatively rich nutritional environment for the implantation and growth of residual endometrial cells, favoring the occurrence of CSE. Consistent with this explanation, all 11 patients in this study who had multiple endometriomas had Pfannenstiel incisions. These research findings demonstrate that the Pfannenstiel incision probably carries a higher risk of CSE than the vertical midline incision. Another interesting result from this study is that deeper endometrioma locations are correlated with longer latency periods. This is probably due to the fact that the deeper endometriomas could not be easily noticed.
Although CSE is a rare event, it manifests as a painful subcutaneous mass and usually bothers the patient for several years. Additionally, CSE can undergo malignant change, which is rapidly fatal and has a survival rate of only 57% [14]. Hence, it is necessary to take precautions to prevent or reduce the occurrence of CSE. On the basis of the implantation theory, we propose a variety of measures: careful flushing and irrigating before closure; using separate needles for uterine and abdominal closure; and not using a sponge to clean the endometrial cavity following complete delivery. Extending the breastfeeding period to delay menstruation has also been proposed for preventing CSE, but without scientific corroboration [21]. In our study, 83.3% (174/209) of the scar endometriomas were located in corner sites of the wound. Therefore, the abdominal wound should be cleaned thoroughly with saline solution before closure, especially the corner sites. Additionally, endometriomas were more common in superficial parts of the abdominal wall, i.e., 12/209 (5.7%) were present in the adipose layer and 135/209 (64.6%) between the adipose layer and the fascia layer, accounting for 70.3% of the total endometriomas. Therefore, careful flushing and irrigation of the adipose layer and fascia layer during closure is critical.
All of the patients in our study underwent surgical excision for the treatment of CSE. Generally, surgical treatment offers the best chance for both making a definitive diagnosis and treating CSE. Medical therapy has a low success rate is associated with adverse effects.
As a retrospective study, some limitations in this study could not be avoided. For example, the data about the CS procedures lacked details such as the layers of closure, type of suture materials, and operation duration. These factors might also affect the occurrence of CSE. To address these questions, further studies will be required in the future.