Anatomy and Clinical Aspects of the Perineum

The perineum refers to the region of the human body located between the vagina and the rectum, extending from the inferior aspect of the pubic symphysis to the coccyx and bounded by the ischiopubic ramus, ischial tuberosities, and the upper border of the sacrotuberous ligaments. The perineum is formed predominantly by the bulbocavernosus and transverse perineal muscles, with the puborectalis muscle and the external anal sphincter contributing additional muscle fibers. The anal sphincter complex lies inferior to the perineal body, with the external anal sphincter composed of skeletal muscle and the internal anal sphincter composed of smooth muscle, continuous with the smooth muscle of the colon.

Perineal trauma can occur during vaginal birth, leading to obstetric anal sphincter injury (OASI), which is associated with significant short- and long-term morbidity. The incidence of some form of perineal trauma is reported to be 85%, and the incidence of trauma requiring suturing ranges from 44% to 79%. Perineal trauma is associated with intense pain that can require pain relief, dyspareunia, fecal incontinence, and can lead to major physical, psychological, and social problems, affecting the ability to care for the newborn and cope with daily tasks of motherhood.

Obstetric perineal lacerations are classified as first to fourth degree, depending on their depth. The repair of these lacerations requires good lighting, visualization, proper surgical instruments, and adequate analgesia. The use of 3-0 polyglactin 910 (Vicryl) suture results in decreased wound dehiscence and less postpartum perineal pain compared with surgical repair using catgut or chromic suture. With severe perineal lacerations involving the anal sphincter complex, irrigation is performed to improve visualization and reduce the incidence of wound infection, and a single dose of a second- or third-generation cephalosporin may be given intravenously before the procedure to reduce the risk of infection.

The perineum is a diamond-shaped space below the pelvic floor, extending between the inferior fascial layer of the pelvic diaphragm and the perineal skin, which is continuous with the skin of the external genitalia. The superficial perineal space contains the erectile tissues, skeletal muscles, and the terminal branches of the internal pudendal vessels and nerves. Knowledge of the anatomy of the perineum is necessary to provide the best surgical outcomes in cases related to trauma, cancer-related extirpation, and congenital abnormalities.

In summary, the perineum is a crucial region of the human body, and understanding its anatomy is essential in providing optimal surgical outcomes and reducing morbidity associated with perineal trauma.