Reevaluating the vesicouterine pouch: histological evidence for optimal dissection planes in oncologic surgery.

During dissection of the vesicouterine pouch, entering from the uterine body side may lead to an inappropriate plane that scrapes the uterine body, whereas dissecting from the bladder side often facilitates smoother separation of the vesicouterine pouch. This suggests that multiple dissectible layers exist in the vesicouterine pouch. In this study, we aimed to investigate the midline structures, which are crucial in oncologic surgeries. Overall, six halves of three cadavers were used. They had no history of lower abdomen or pelvic condition. No fasciae or septum-like structures were observed between the bladder and uterine and vaginal walls. A magnified image revealed several layers of connective tissue that were irregularly interspersed between the muscular layer of the bladder and vagina. Histological analysis demonstrated that the vesicouterine pouch consists of multiple dissectible layers, differing from descriptions in traditional surgical textbooks. Specifically, the pubocervical fascia and vesicovaginal septum were absent in the mid-sagittal section. Instead, multiple layers of connective tissue were irregularly interspersed within the bladder's muscular layer. This finding is particularly important in oncologic surgeries, as it highlights the risk of cancer exposure at the dissection margins in cases with deep muscular invasion or stromal invasion. Additionally, it suggests that initiating dissection from the bladder side facilitates entry into the correct dissectible plane, reducing the risk of exposing malignant tissue.