Posterior Vaginal Compartment Anatomy: Implications for Surgical Repair.

OBJECTIVES: To examine the gross and histologic anatomy of the proximal, mid, and distal posterior vaginal compartment and discuss implications for surgical repair.

STUDY DESIGN: In this cadaver study, pelvic organs were resected en bloc, immersed in formalin solution, and transected in the mid sagittal plane. Measured distances included: posterior vaginal wall length, cervicovaginal junction or vaginal cuff to posterior peritoneal reflection, peritoneal reflection to proximal edge (apex) of perineal body, and perineal body apex to hymenal remnant (height). The posterior vaginal wall was divided into 3 segments along the midsagittal plane and submitted in whole tissue blocks for staining. Histologic analysis included that of 2 young nulliparous women whose tissue was harvested within 12 hours of death.

RESULTS: Eleven cadavers were examined. Median (interquartile range [IQR]) posterior vaginal length was 7.6 (2.2) cm. The peritoneum attached to the posterior vaginal wall a median (IQR) of 1.3 cm (0.5 cm) distal to the cervicovaginal junction (n = 8). The rectovaginal space, spanning from the peritoneal reflection to perineal body apex, had a median (IQR) length of 4.7 cm (2.1 cm). Microscopic examination of the mid segment revealed a layer of loose fibroadipose tissue between the vaginal/rectal walls, with no distinct dense fibroconnective tissue layer. The median (IQR) perineal body height was 2.3 cm (1.2 cm). No discrete fibrous capsule was seen surrounding the external anal sphincter muscle.

CONCLUSIONS: These findings support evidence showing absence of a rectovaginal fascia. The anal sphincter lacks a fibrous capsule, which is important during closure of third-/fourth-degree obstetric lacerations.