Surgical anatomy of the vaginal introitus

Abstract

Aim: The vaginal introitus is the entrance to the vagina, encompassing the anterior and posterior vestibules and the perineum. The surgical anatomy of the vaginal introitus, the lowest level of the vagina, has not been subject to a recent comprehensive examination and description. Vaginal introital surgery (perineorrhaphy) should be a key part of surgery for a majority of pelvic organ prolapse.

Methods: Cadaver studies were performed on the anterior and posterior vestibules and the perineum. Histological studies were performed on the excised perineal specimens of a cohort of 50 women undergoing perineorrhaphy. Included are pre- and postoperative studies which were performed on 50 women to determine the anatomical and histological changes achieved with a simple (anterior) perineorrhaphy.

Results: The vaginal introitus is equivalent to the Level III section of the vagina, measured posteriorly from the clitoris to the anterior perineum then down the perineum to the anal verge. The anterior and posterior vestibules, with nonkeratinizing epithelium, extend laterally to the keratinized epithelium of the labia minora (Hart's line). The anterior vestibule has six anatomical layers while the posterior vestibule has three. The perineum has an inverse trapezoid shape. Perineorrhaphy specimens were a mean 2.9 cm wide and 1.6 cm deep. They show squamous epithelium with loose underlying connective tissue. There were no important structures seen histologically, for example, ligaments or muscles. Microscopically, only 6 (12%) were completely normal with 44 (88%) showing minor changes including inflammation and scarring. Considerable anatomical benefits were achieved with such a perineorrhaphy including a 27.6% increase in the perineal length and a 30.8% reduction in the genital hiatus.

Conclusion: An understanding of the anatomy and histology of the vaginal introitus can assist with performing a simple and effective perineorrhaphy, the main surgical intervention at the vaginal introitus.

Keywords: anterior vestibule; perineorrhaphy; perineum; posterior vestibule; prolapse; vaginal introitus.

Figure 1

Vaginal introitus is Level III of the vagina incorporating anterior and posterior vestibules and the perineum down to the anal verge.

Figure 2

Vaginal introitus: anterior and posterior vestibule (as outlined by Hart's line), and the perineum (within the yellow line extension to Hart's line to the anal verge).

Figure 3

Superficial dissection of the anterior and posterior vestibules: urethra marked by probe (U), crus of the clitoris (CC), superficial perineal fascia (SPF), perineal membrane (PM), superficial transversus perinei muscle (STPm), fourchette (F), bulbospongiosus muscle (BSm), sphincter ani externus (SAE), anus (A). Fuller description in Haylen et al.

Figure 4

Dissection of the posterior vestibule: subcutaneous tissue (ScT); perineal body (PB). Fuller description in Haylen et al.

Figure 5

Inverse trapezoid

Figure 6

(A) Perineal gap (PG): thinned out medial area (cm) between Moynihan forceps placed bilaterally where the labia minora meet the perineum., , ,  (B) Perineorrhaphy width (PW) and perineorrhaphy depth (PD).

Figure 7

Perineal length (PL): distance from posterior margin of vestibule to anterior anal verge.,

Figure 8

Mid‐perineal thickness (MPT): thickness (cm) of the mid‐perineum in the midline.,

Figure 9

Genital hiatus: middle of the external urethral meatus to the posterior aspect of the hymen., ,

Figure 10

(A) Perineal gap (before excision); (B) perineal gap (after excision); (C) reconstituted perineum.

Figure 11

Excised perineum showing (A) lichen sclerosis; (B) inflammation and scarring.