Move the probe with a parallel shift medial to the ischiocavernosus muscle in the anterior perineal triangle until the superficial and deep transverse muscles are visualized.

The pudendal nerve runs alongside the internal pudendal artery in the Alcocks canal along the medial margin of the inferior pubic ramus deep to the muscles of the superficial pelvic floor.

In the ilioanal fossa below the levator ani, the pudendal nerve has three branches: the inferior rectal branch, the perineal branch, and the dorsal nerve of the penis (blue arrow).

Alcocks canal (synonym: pudendal canal) is a fascial compartment on the lateral wall of the ischioanal fossa that contains the pudendal nerve, the internal pudendal artery and the internal pudendal vein.

Place the patient supine with the pelvis elevated by a pillow. Hips and knees are flexed and the thighs are abducted with external rotation.

Place the linear high-frequency probe on a line between the scrotum/mons pubis and the lateral border of the anus on top of the ischiopubic ramus. Visualize the ischiocavernosus muscle on top of the ischiopubic bone.

The pudendal nerve exits the pelvis through the greater sciatic foramen, curls around the sacrospinous ligament and enters the ischioanal fossa through the lesser sciatic foramen.

The lesser sciatic foramen is formed by the sacrospinous ligament and the sacrotuberous ligament.

The external anal sphincter origins from the perineal body and inserts on the anococcygeal ligament. It is innervated by the inferior rectal branch of the pudendal nerve.

The pudendal nerve origins from the spinal nerves S2-S4 and whirls around the ischial spine.

The anatomical space called the ischioanal fossa (synonym: the ischiorectal fossa) is the space inferior and lateral to the levator ani, lateral to the anal canal, medial to the internal obturator muscle, and superior to the urogenital diaphragm (syn: the superficial pelvic floor).

The ischioanal fossa mainly contains fat but also the pudendal canal (synonym: the Alcock’s canal) on the lateral wall of the ischioanal fossa. The pudendal canal contains the pudendal nerve and the internal pudendal blood vessels.

The muscles of the deep pelvic floor are known as the levator ani muscles. The deep pelvic floor has two components: The pubovisceral and the iliococygeal muscles. The pubovisceral muscles are the pubococcygeus and the puborectalis muscles.