Background: Hydrosalpinx is when the fallopian tube is damaged, and its distal portion is dilated and filled with fluid. The exact mechanisms behind hydrosalpinx's adverse effects on pregnancy are poorly understood. The hydrosalpinx fluid is believed to retrograde into the uterine cavity. It harms the endometrium by altering endometrial receptivity markers and creating a local inflammatory response following a significant elevation in inflammatory cytokines such as interleukin-2 (IL-2). Objective: We evaluated whether surgical removal of hydrosalpinx can subside endometrial inflammatory response by modifying the endometrial leukocyte populations in the fourth-post treatment cycle. Materials and Methods: In this study, 10 infertile women with moderate to severe hydrosalpinges (sono visible, diameter > 10 mm) confirmed by hysterosalpingography or laparoscopy who underwent laparoscopic salpingectomy from January 2021 to January 2022 were evaluated for endometrial pathologic examination. The inclusion criteria were a normal hormonal profile, body mass index (18-28 kg/m 2 ), and regular menstrual cycle confirmed by mid-luteal progesterone levels of >10 ng/mL. Mid?luteal?phase endometrial sampling was performed at the time of surgery. Patients were followed up for a second endometrial biopsy in the mid-luteal phase of the fourth-post treatment cycle. Ten age-matched egg donor women with a history of successful pregnancy were enrolled in the study as a control group and underwent endometrial biopsy in the mid-luteal phase. Control and hydrosalpinx endometrial samples were obtained by pipeline. All participants did not use hormonal medication for three months before salpingectomy and signed the informed consent form. After sample collection, tissues were prepared for hematoxylin and eosin staining. 5 representatives adjacent, nonoverlapping high-power fields (400×) were examined for pre and post-salpingectomy endometrium. The leukocyte count was recorded as the number of neutrophils, plasma cells, lymphocytes, basophils, eosinophils, and macrophages. Results: Evaluation of the H&E-stained slides of the endometrium showed a statistically significant increase in the overall number of inflammatory cells in cases before surgery versus control groups (94.66 ± 27.60 vs. 45.33 ± 13.73, p = 0.02). Moreover, there was a statistically significant decrease in the number of lymphocytes (36.16 ± 10.59 vs. 86.66 ± 26.39, p = 0.027) after surgery compared to pre-surgery samples. There were no differences in the number of neutrophils, plasma cells, eosinophils, or macrophages in the pre and post-surgery samples (p > 0.05). Conclusion: Our findings suggest that local inflammatory response of endometrium is present in the endometrium exposed to hydrosalpinges fluid, and surgical removal of the hydrosalpinx before In vitro fertilization program effectively subsides the endometrial inflammation through a significant decrease in the lymphocyte population.
