Pain syndrome features in different forms of external genital endometriosis: a cross-sectional study

Objective: To assess pain syndrome in patients with different forms of external genital endometriosis.

Materials and methods: The one-stage study was conducted at the V.I. Kulakov National Medical Research Center for Obstetrics, Gynecology & Perinatology of the Ministry of Health of the Russian Federation from 2021 to 2023, involving 200 patients (age 32.03 (7.15) years) with confirmed endometriosis through expert ultrasonography and magnetic resonance imaging of the pelvic organs. Patients were categorized into three groups based on the form of endometriosis: with peritoneal endometriosis (SUP), endometriomas (OMA), and deep endometriosis (DE); in case of combined pathology inclusion in one or another group was carried out according to the most severe form. The targeted history collection of women was conducted through questioning. The intensity of the pain syndrome was evaluated using the visual analog scale (VAS), followed by calculation of the pelvic pain index (PPI). The level of central sensitization (CS) was assessed using the CSI scale, and quality of life and sexual function were evaluated using the SF-12 questionnaire and 5-point Likert scale, respectively. Neuropathic components were assessed based on the results of the PainDetect questionnaire.

Results: Data analysis revealed that patients with OMA were predominantly not characterized by pain syndrome. The severity of dysmenorrhea, chronic pelvic pain, and PPI, according to VAS indicators, was minimal in isolated endometriomas, with a tendency for higher PPI when endometriomas were combined with SUP, DE, and all three forms of endometriosis, respectively. PPI determination revealed that a threshold score of ≥3.8 points can indicate the presence of DE. Additionally, a significant level of sensitization (≥40 points) was observed in nearly one in two women with DE, one in three women with SUP, and one in six women with OMA. The presence of a neuropathic component was generally less common in patients with endometriosis (5.0%).

Conclusion: The study results demonstrated that not only the presence of pain but also the degree of its severity play a significant role in the diagnosis of endometriosis. PPI can serve as a tool to identify women at risk of endometriosis at the outpatient examination stage. A PPI score ≥3.8 points may indicate DE. The study results led to the conclusion that CS significantly contributes to pain genesis in patients with endometriosis-associated pelvic pain, while the neuropathic component plays a lesser role.