Endometriosis is one of the challenges for women with pelvic pain and infertility. Chronic pelvic pain affects about 15% of women of childbearing age and reduces their quality of life [15]. In the present study, the mean age of patients was 32.4 years, and the disease was highly severe in less than half of the cases, which is consistent with the findings of Khawaja et al [16]. The infertility rate in women with endometriosis in our study was 37.3%, which is consistent with the study of Radhika et al [17]. And Bellelis et al. [18], reported infertility rate as 31.5% and 40%, respectively.
This study aimed to explore the relationship between the severity of endometriosis symptoms (dyspareunia, dysmenorrhea and chronic pelvic pain) and the spread of the disease. The results show that only the severity of dyspareunia is related to the stage of endometriosis, and the odds ratio of endometriosis was 0.24 in the absence of dyspareunia. In previous studies, many attempts have been made to clarify the relationship between the type and location of lesions and the spread of the disease with the severity and symptoms of the disease, which has had no consensus on results [19].
The mechanism of severe pain in endometriosis is the growth of nerve fibers into ectopic implants [20-22]. According to the study by Varecellini et al. [19], dysmenorrhea, one of the most common symptoms of endometriosis, was associated with atypical and popular implants. Fedele et al. [23] reported the association of dysmenorrhea with advanced stages of endometriosis. Chapron et al. [24], showed that dysmenorrhea was associated with the size and depth of the lesions. However, in other studies, there was no association between menstrual pain and endometriosis [25], which shows that other factors play a role in causing this pain, and merely examining the appearance of implants can reveal the true nature of the disease.
In our study, there was no association between dysmenorrhea and chronic pelvic pain with disease severity. This finding are inconsistent with that of Varcellini et al. [19], who found a significant association between disease severity and dysmenorrhea and chronic pelvic pain. Although their estimated odds ratio for dysmenorrhea and chronic pelvic pain (1.33 and 1.01, respectively) was very close to one and indicates not strong correlation, a slight change in the samples volume possibility causes the missing of the confidence interval.
Results of the present stdudy suggested that there is a significant relationship between dyspareunia and posterior DIE lesion, it has been strongly confirmed in other studies. Anatomically, the most stretched area during intercourse is the retro-cervical area [26], which indicates the organic nature of this pain. In the study of Anaf et al. [27], the histological relationship between nerves and endometriotic foci in retro-cervical nodules was found [28]. Besides, Douglas stenosis was significantly associated with dyspareunia in the present study, which has been reported in almost all previous studies. Varcellini et al., reported a strong association between Douglas pouch lesions and dyspareunia [19].
Studies show that the association between ovarian endometriosis and dysmenorrhea has conflicting results. Although endometrioma was common among the patients in our study (83.4%), no significant association was found between endometrioma and dysmenorrhea, which is consistent with the findings of some reasearchers (Radhika et al. [17], Porpora et al. [29], Chapron et al. [24], and Koninckx et al [30]). In contrast, Muzii et al. [31] and Fedele et al’s study. [23], the association between endometrioma and pelvic pain was significant, which is inconsistent with results of the present study.