Does deep endometriosis infiltrating the uterosacral ligaments present an asymmetric lateral distribution?

Objective: To investigate whether deeply infiltrating endometriosis occurs with equal frequency between left and right uterosacral ligaments. Design: Retrospective analysis of consecutive cases. Setting: Department of gynaecological surgery in a tertiary care university hospital in Paris, France. Population: One hundred and thirty consecutive women with laparoscopic resection of histologically proven deep endometriosis infiltrating the uterosacral ligaments. Methods: Laterality, intraoperative aspect of the uterosacral ligaments, and associated endometriosis were recorded during laparoscopy. Deep endometriosis infiltrating the uterosacral ligaments was considered as histologically proven in the presence of endometrial glands and stroma. Main outcome measure: Frequency of left- and right-sided deep endometriosis infiltrating the uterosacral ligaments. Results: The left uterosacral ligament alone was involved in 69 cases; the right uterosacral ligament alone was involved in 38 cases; both were involved in 23 cases. For patients with unilateral deep endometriosis infiltrating the uterosacral ligaments the observed proportion of endometriosis involving the left uterosacral ligament (69/107, 64.5%) was significantly different from the expected proportion of 50% (X² = 8.98; P <0.01). Conclusion: Anatomical differences between left and right hemipelvis and differences in the frequency of ovulation between right and left ovary could explain these results.